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  • bioavailability  (303)
  • Animals
  • EARTH RESOURCES AND REMOTE SENSING
  • General Chemistry
  • Inorganic Chemistry
  • Springer  (305)
  • 2015-2019
  • 1990-1994  (108)
  • 1980-1984  (131)
  • 1975-1979  (66)
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  • 1
    Electronic Resource
    Electronic Resource
    Effect of taurine, l-glutamine and l-histidine addition in an amino acid glucose solution on the cellular bioavailability of zinc (1994)
    Springer
    BioMetals 7 (1994), S. 237-243 
    Details
    ISSN: 1572-8773
    Keywords: taurine ; l-glutamine ; l-histidine ; total parenteral nutrition ; zinc ; bioavailability ; fibroblasts
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Radioactive zinc was used to study the effect of a binary parenteral nutrient solution, composed of amino acids and glucose, on zinc uptake by fibroblasts. The influence of addition of taurine, l-glutamine and of the increase in l-histidine content of the admixture was assessed. The pure mixture was highly toxic for cells and so it was diluted 1/5 in tyrode buffer with 2% albumin. As compared with cells incubated in the buffer containing albumin, zinc absorption was significantly higher (P 〈 0.05) in the presence of the amino acids of the mixture. Amino acids thus increased bioavailability by displacing zinc bound to albumin. When the histidine concentration in the nutrient medium (4.2 mm) was doubled, inhibition was noted after 30 min of incubation and zinc uptake thereafter remained comparable to that in histidine-free medium. The addition of glutamine (4.2 mm), usually not present in binary mixtures, resulted in significant differences as compared with glutamine-free control medium. Taurine (0.8 mm), led to a constant increase in zinc uptake by fibroblasts as compared with that obtained with taurine-free mixture. However, ultrafiltration showed that taurine was not able to displace zinc from albumin.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00149554
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  • 2
    Electronic Resource
    Electronic Resource
    Differences in the bioavailability of dihydrotachysterol preparations (1994)
    Springer
    European journal of clinical pharmacology 47 (1994), S. 81-84 
    Details
    ISSN: 1432-1041
    Keywords: Dihydrotachysterol ; bioavailability ; pharmacokinetics ; human ; HPLC
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Abstract The bioavailability of four preparations containing dihydrotachysterol (DHT2) was tested in two separate trials with administration of single, oral doses of 1 mg per individual. The relative bioavailability of corresponding preparations (capsules vs capsules and oral solution vs oral solution) was tested in a randomised, crossover pattern within the same group of volunteers. Two different groups of 24 healthy volunteers took part in each trial. Solution and capsule bioavailability was also compared inter-individually. A new sensitive HPLC-method (quantification limit 0.5 ng · ml-1) was used for the measurement of DHT2 concentration in serum. Three of the preparations tested had a similar bioavailability (mean AUC values of 195.5–223 ng · h · ml-1); the bioavailability of the fourth preparation (A.T.10 oral solution) was considerably lower (mean AUC value 111.5 ng · h · ml-1). The present dosage recommendations of all four preparations are identical. A new dosage recommendation is thus required for the oral solution with low bioavailability (A.T.10).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00193484
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  • 3
    Electronic Resource
    Electronic Resource
    Doxycycline carrageenate — an improved formulation providing more reliable absorption and plasma concentrations at high gastric pH than doxycycline monohydrate (1994)
    Springer
    European journal of clinical pharmacology 46 (1994), S. 143-146 
    Details
    ISSN: 1432-1041
    Keywords: Doxycycline ; bioavailability ; pH dependent absorption ; pharmacokinetics ; carrageenate ; adverse events
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Abstract The effect of increased gastric pH (obtained by pre-treatment with omeprazole) on the bioavailability of doxycycline monohydrate and doxycycline carrageenate has been investigated in 24 healthy volunteers, using an open, randomised, four-treatment, four-period, crossover, 2×2 factorial design. Each subject received a single dose of 100 mg of each of the doxycycline formulations with and without pre-treatment with omeprazole (40 mg daily for 7 days). The two formulations were bioequivalent (rate and extent) during fasting without omeprazole pre-treatment, whereas after omeprazole, the monohydrate showed a highly significant decrease in bioavailability (38% for AUC and 45% for Cmax) compared to the carrageenate formulation, which was not affected by prior administration of omeprazole. Many of the subjects did not reach a therapeutic plasma level of doxycycline during the combination of omeprazole and doxycycline monohydrate, and most adverse events (mainly gastrointestinal) were reported after this combination. As large populations of patients have a high gastric pH due to frequent use of H2-blockers, proton pump inhibitors and antacids, as well as to physiological achlorhydria, the decreased absorption of doxycycline monohydrate may well have a clinical impact, for example when the patients are treated with tetracyclines for an infection.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00199878
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  • 4
    Electronic Resource
    Electronic Resource
    Receptor binding assays in analysing the bioavailability and pharmacodynamic bioequivalence of active drug moieties (1994)
    Springer
    European journal of clinical pharmacology 46 (1994), S. 237-242 
    Details
    ISSN: 1432-1041
    Keywords: Metoprolol ; bioavailability ; bioequivalence ; receptor binding assay ; pharmacokinetics ; sustained release formulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Abstract The bioavailability and pharmacodynamic bioequivalence of a conventional and an experimental sustained-release formulation of 100 mg metoprolol tartrate were studied in a randomised cross-over study in seven healthy volunteers by assessing over 24 h the plasma kinetics of R,S-metoprolol, its β1-adrenoceptor binding component, and by determining the extent to which the active drug moiety in plasma occupied rabbit lung β1-and rat reticulocyte β2-adrenoceptors. The formulations differed markedly in their kinetic characteristics: the peak plasma concentration (Cmax) of R,S-metoprolol after administration of the conventional formulation was 140 ng·ml−1, (n=7) and it was approximately one-third of that after the sustained-release formulation, 49 ng·ml−1, (n=6); the AUC0–24 h-values for the formulations were 700 and 310 ng·h·ml−1, respectively. The Cmax for the β1-adrenoceptor binding component of metoprolol was 180 ng·ml−1 (n=7) after administration of the conventional, and 74 ng·ml−1 after administration of the sustained-release formulation. The corresponding AUC0–24 h-values for the receptor binding component were 920 and 470 ng·h·ml−1 (n=7). Thus, the kinetic differences between R,S-metoprolol and the β1-receptor binding component were considerable and they were affected by the type of formulation. In general, after administration of the sustained-release formulation, the percentage β1- and β2-adrenoceptor occupancy of metoprolol in plasma was 5–15% less than after administration of the conventional formulation. At 0.5–1.5 h after drug intake the average β1-adrenoceptor occupancy of the conventional formulation varied between 80–90% and that of the sustained release formulation between 20–76%. At these times the differences in receptor occupancy were significant; at 0.5–2 h after drug intake the average β2-adrenoceptor occupancy of the conventional formulation varied from 20–30%, and that of the sustained-release formulation was 2–17%. At other times the difference in receptor occupancy between the formulations was not significant. The results demonstrate that plasma concentration-kinetics were more discriminating than β-adrenoceptor-binding in analysing bioequivalence. It was possible to determine the bioavailability of the active ingredient of metoprolol and to study pharmacodynamic bioequivalence by using receptor binding assays.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00192555
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  • 5
    Electronic Resource
    Electronic Resource
    Conventional and controlled release diltiazem (1994)
    Springer
    European journal of clinical pharmacology 47 (1994), S. 75-79 
    Details
    ISSN: 1432-1041
    Keywords: Diltiazem ; Angina pectoris ; controlled release formulation ; metoprolol ; bioavailability ; pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Abstract Diltiazem CR tablets 120 mg b.i.d. for 1 week were compared with plain tablets 60 mg q.i.d. in 13 healthy male volunteers in a study of pharmcokinetic variables. Their antianginal efficacy was also compared in 23 patients with stable angina pectoris who were already on metoprolol. Both studies were of randomised, cross over design, and the clinical study was double blind. The pharmacokinetic variables of the two formulations were very similar except for the longer tmax of 4.4 h for diltiazem CR in comparison to 2.9 h for the plain tablets. The mean relative bioavailability of diltiazem CR in comparison with plain tablets was 1.14. The clinical study showed that after four weeks on diltiazem CR 120 mg b.i.d. or diltiazem plain tablets 60 mg q.i.d. in addition to metoprolol, there were significant decreases in weekly anginal attacks from 11 to 5 attacks/week, the number of nitroglycerin tablets consumed from 6 to 3 tablets/week, and an increase in the maximum workload from 116 to 126 and 123 W for diltiazem CR and plain diltiazem tablets, respectively, as compared to placebo. Five of the patients were angina free during diltiazem treatment. No difference in antianginal efficacy between the two preparations was seen. It was concluded that CR 120 mg b.i.d. appears bioequivalent to plain diltiazem tablets 60 mg q.i.d.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00193483
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  • 6
    Electronic Resource
    Electronic Resource
    The pharmacokinetics of recombinant human erythropoietin after subcutaneous injection at different sites (1994)
    Springer
    European journal of clinical pharmacology 46 (1994), S. 333-337 
    Details
    ISSN: 1432-1041
    Keywords: Erythropoietin ; recombinant human erthropoietin ; pharmacokinetics ; subcutaneous ; absorption ; bioavailability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Abstract The pharmacokinetics of recombinant human erythropoietin (RhEPO) were investigated after subcutaneous (s.c.) injection in the thigh and in the abdominal wall. Eleven healthy subjects, age 24.4 years (median), were studied. Each subject received two s.c. injections of 100 U·kg-1 RhEPO dissolved in 1 ml water: one injection in the thigh and another in the abdomen. Serum erythropoietin was measured regularly by radioimmunoassay until 144 h after each injection. The mean residence time was significantly longer after injection in the thigh than in the abdomen (32.7 vs 26.2 h). The estimated half-life of absorption was significantly longer after injection in the thigh than after abdominal application (14.9 vs 12.3 h). The estimated half-life of elimination was not significantly different (4.4 vs 4.8 h). The relative difference in the area under the curve between injection in the abdomen and the thigh in the same subject ranged from -36% to +68% but there was no significant difference in bioavailability. The peak concentration was not significantly different and appeared at around 10 h (Cmax thigh, 175 U·l-1 vs Cmax abdomen, 216 U·l-1). A twin-peak configuration of the concentration vs time curve with a significant second peak at 24 h was found after injection in the thigh but not after abdominal injection. In conclusion, the mean residence time was longer after administration in the thigh, probably due to delayed absorption, but bioavailability was not significantly different. Following injection in the thigh the concentration curve had two peaks. The differences may be due to regional variations in lymph flow and to physical activity. The overall differences in pharmacokinetics appeared to be too small to recommend a general preference of the injection site.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00194401
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  • 7
    Electronic Resource
    Electronic Resource
    Effect of diet on the single- and multiple-dose pharmacokinetics of sustained-release ketoprofen (1994)
    Springer
    European journal of clinical pharmacology 47 (1994), S. 361-366 
    Details
    ISSN: 1432-1041
    Keywords: Ketoprofen ; diet ; bioavailability ; pharmacokinetics ; sustained release
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Abstract The indirect effect of diet on the single-and multiple-dose pharmacokinetics of sustained-release ketoprofen was studied in 16 healthy male volunteers. In an open, cross-over design, 200 mg ketoprofen was administered as a gastric-juice-resistant, sustained-release tablet once daily during two periods of 5 days. A low-calorie/low-fat diet (LCFD) was given in the first period and a high-calorie/high-fat diet (HCFD) in the second period. The first meal on each day was given 4 h after drug intake. Ketoprofen plasma concentrations were measured over 24 h after the first dose on day 1 and over 36 h after the final dose on day 5 of each period. On average, plasma concentrations of ketoprofen were higher with the LCFD than with the HCFD. With the HCFD there was a tendency to longer absorption-lag times on day 5. The maximum concentration and the area under the curve over one 24-h dosage period (AUC0–24) were significantly higher with the LCFD, both on day 1 and on day 5. For AUC0–24 the differences were on average 15% (day 1) and 24% (day 5). The same tendency was observed for the amount excreted in urine over 24 h (Ae), but the difference was only significant on day 1 (14%). The elimination rate constant (Kβ) and the mean residence time were similar for the two diets, both on day 1 and on day 5. From these results, we conclude that there was an acute indirect effect of diet when a meal was had 4 h after intake of the medication. This resulted in a greater extent of ketoprofen absorption with the LCFD than with the HCFD. The absorption rate was apparently not influenced by this acute effect. The longer gastric residence time of ketoprofen with the HCFD may be the result of a long-term indirect effect on gastric emptying rate. If the extreme difference between the diets in this study is taken into account, it seems unlikely that the observed indirect effects have implications for clinical practice.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00191169
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  • 8
    Electronic Resource
    Electronic Resource
    Frequency response method in pharmacokinetics (1994)
    Springer
    Journal of pharmacokinetics and pharmacodynamics 22 (1994), S. 293-307 
    Details
    ISSN: 1573-8744
    Keywords: linear dynamic system ; frequency response ; frequency response method ; weighting function ; bioavailability ; gentamicin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The paper presents the demonstration of applicability of the frequency response method in a bioavailability study. The frequency response method, common in system engineering, is based on an approximation of the frequency response of a linear dynamic system, calculated from input-output measurements, by a frequency model of the system transfer function in the frequency domain. In general, the influence of the system structure on the form of the system frequency response is much more distinct than on the form of the system output. This is of great advantage in modeling the system frequency response instead of the system output, commonly used in pharmacokinetics. After a brief theoretical section, the method is demonstrated on the estimation of the rate and extent of gentamicin bioavailability after intratracheal administration to guinea pigs. The optimal frequency model of the system describing the gentamicin pathway into the systemic circulation and point estimates of its parameters were selected by the approximation of the system frequency response in the frequency domain, using a noniterative algorithm. Two similar estimates of the system weighting function were independently obtained: the weighting function of the selected frequency model and the weighting function estimated by the numerical deconvolution procedure. Neither of the estimates of the weighting function does decrease monotonously after the maximum of about 2.2–2.5 unit of dose·hr−1 recorded approximately 0.1 hr after drug administration. Both estimates show a marked additional peak approximately at 0.3 hr after administration and possible peaks in the further time period. We hypothesized that the loop found in the frequency response calculated and in the selected optimal frequency model, the high-order of this model, and several peaks identified in the estimates of the system weighting function indicated the complexity of the system and the presence of time delays. Three estimates of the extent of gentamicin intratracheal bioavailability obtained by the three different ways: directly from the calculated frequency response, calculated using the selected frequency model, and by the deconvolution method were 0.950, 0.934, and 0.907 respectively. Thus the conclusion can be made that gentamicin injected intratracheally to guinea pigs is almost completely available.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02353623
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  • 9
    Electronic Resource
    Electronic Resource
    Bioavailability of Flumequine After Semisimultaneous Administration to Veal Calves (1994)
    Springer
    Pharmaceutical research 11 (1994), S. 117-121 
    Details
    ISSN: 1573-904X
    Keywords: flumequine ; bioavailability ; semisimultaneous administration ; method evaluation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The absolute bioavailability of flumequine after semisimultaneous intramuscular administration as a water-based suspension to veal calves was 92 ± 14%. The semisimultaneous experimental design provided a reliable determination of absorption rate and demonstrated flip-flop pharmacokinetics. No period or sequence effects were detected. Calculated elimination rate, clearance, and volume of distribution after intravenous administration were comparable to values obtained from traditional design studies. The semisimultaneous experimental design proved to be valuable for the assessment of bioavailability and pharmacokinetics of drugs in food-producing animals while preventing violation of basic clearance assumptions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1018962131274
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  • 10
    Electronic Resource
    Electronic Resource
    Percutaneous Absorption of 2′,3′-Dideoxyinosine in Rats (1994)
    Springer
    Pharmaceutical research 11 (1994), S. 809-815 
    Details
    ISSN: 1573-904X
    Keywords: 2′,3′-dideoxyinosine ; transdermal ; bioavailability ; follicular density ; penetration enhancer
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract This study explored the topical route for administering of 2′,3′-dideoxyinosine (ddI), a nucleoside analog used for treating patients with acquired immunodeficiency syndrome. A dose of ddI (∼180 mg/kg) dispersed in ~1 g ointment base was applied, with or without occlusion, to the back of high follicular density (HFD) and low follicular density (LFD) rats. The systemic ddI clearance was determined using a concomitant administration of an intravenous tracer dose of [3H]ddI. At 24 hr, the experiment was terminated and skin sections at the application site were removed. After topical application, average plateau plasma levels of about 0.6 µg/ml were achieved within 1 to 2 hr and maintained for 24 hr. Occlusion gave a more uniform plasma profile but did not increase the bioavailability. The systemic bioavailability in HFD and LFD rats was about the same at 33%. In addition, a depot of about 16% of the dose was recovered by rinsing the application area and extracting the drug from the excised application site. These data indicate that about 50% of the dermal dose penetrated the skin barrier in 24 hr. The similar bioavailability in the HFD and LFD rats further suggests an unimportant role for the transfollicular absorption route for ddI. The effect of a mixture of penetration enhancers, Azone and propylene glycol (5:95), was studied in HFD rats. Coadministration of ddI with the enhancers did not increase the ddI bioavailability. However pre-treatment and coadministration with the enhancers significantly increased the bioavailability to 62%, which is a conservative estimate because the plasma drug level was still at a plateau when the experiment was terminated at 24 hr. In summary, the transdermal bioavailability of ddI exceeded the 15% oral bioavailability found in previous studies by more than 3 folds and was further increased by the pretreatment with absorption enhancers. These data indicate the topical route as an attractive administration route.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1018965305234
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  • 11
    Electronic Resource
    Electronic Resource
    Bioavailability of phosphorus in agriculturally loaded rivers in southern Finland (1994)
    Springer
    Hydrobiologia 287 (1994), S. 179-194 
    Details
    ISSN: 1573-5117
    Keywords: agriculture ; phosphorus ; bioavailability ; bioassays ; isotherms ; eutrophication
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The potential bioavailability of phosphorus in agriculturally loaded rivers of southern Finland was determined by an algal bioassay and the release of the potentially bioavailable particulate P was estimated by sorption studies. According to the bioassay 0 to 13.2 per cent (mean 5.1%) of the particulate P in river water samples was potentially bioavailable. Dissolved reactive P (DRP) in river waters appeared to be totally bioavailable whereas the dissolved unreactive P appeared not to be utilized by algae. In addition to river waters two lake sediment samples were also assayed. In these samples 0 and 2.6% of the P was bioavailable. The potential bioavailability of particulate P in agriculturally loaded rivers obtained in this study was lower than that reported in studies from other countries. The difference was assumed to arise partly from methodological factors and partly from the nature of the Finnish soils. The EPC (equilibrium phosphate concentration) values indicated that during the period when most of the agricultural loading enters the lakes in Finland, potentially bioavailable P is not released from the particles because of the relatively high DRP concentration in the receiving waters. However, during the algal production period the DRP concentration in lakes decreases below the EPC and potentially bioavailable particulate P is desorbed. The increase in pH during this period may further enhance the desorption of P.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00010733
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  • 12
    Electronic Resource
    Electronic Resource
    Enhanced biodegradation of phenanthrene in a biphasic culture system (1994)
    Springer
    Biodegradation 5 (1994), S. 93-103 
    Details
    ISSN: 1572-9729
    Keywords: biodegradation ; PAH ; phenanthrene ; Pseudomonas aeruginosa ; bioavailability ; 2,2,4,4,6,8,8-heptamethylnonane ; surfactants
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Energy, Environment Protection, Nuclear Power Engineering , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Degradation of phenanthrene byPseudomonas aeruginosa AK1 was examined in (i) an aqueous mineral salts medium to which phenanthrene particles of varying size (i.e. diameter) were added, and (ii) an aqueous/organic biphasic culture system consisting of mineral salts medium supplemented with 2,2,4,4,6,8,8-heptamethylnonane (HMN) as the phenanthrene-carrying organic phase. In both systems, the rate of phenanthrene biodegradation could be significantly enhanced by manipulations leading to improved phenanthrene mass transfer into the aqueous phase. With crystalline phenanthrene, the rate of biodegradation was found to be directly correlated to the particle surface area, whereas in the biphasic system the rate of biodegradation of the dissolved phenanthrene was mainly governed by the HMN/water interface area. In the latter system, exponential growth with a doubling time t d of 6–8 hours has been achieved under conditions of intensive agitation of the medium indicating that phenanthrene degradation by strain AK1 is limited mainly by physicochemical parameters. Addition of selected surfactants to the culture medium was found to accelerate phenanthrene degradation by strain AK1 only under conditions of low agitation (in the presence of HMN) and after pretreatment of phenanthrene crystals by ultrasonication (in the absence of HMN). Evidence is presented that the stimulating effect of the surfactants was primarily due to improved dispersion of phenanthrene particle agglomerates (in the aqueous mineral salts medium supplemented with phenanthrene crystals) or of the phenanthrene-carrying lipophilic solvent drops (in the aqueous/organic biphasic culture system) whereas the solubilizing activity towards phenanthrene was neglectible. Under conditions of intensive mixing of the culture medium (i.e. if a high particle surface area or HMN/water interface area, respectively, is provided), the addition of surfactants did not enhance phenanthrene biodegradation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00700634
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  • 13
    Electronic Resource
    Electronic Resource
    Oral Absorption of Peptides: The Effect of Absorption Site and Enzyme Inhibition on the Systemic Availability of Metkephamid (1994)
    Springer
    Pharmaceutical research 11 (1994), S. 528-535 
    Details
    ISSN: 1573-904X
    Keywords: absorption ; peptides ; metkephamid ; bioavailability ; degradation ; permeability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract In this study the intestinal degradation and absorption of a synthetic pentapeptide, metkephamid, were investigated in the rat by determination of its wall permeabilities in the small and large intestine and the extent and mechanism of its intestinal degradation. The peptide was metabolized in the gut wall through contact with membrane-bound enzymes in the brush border membrane. The extent of metabolic inactivation depended on the intestinal segment investigated and decreased in the axial direction. No metabolism was found in the colon. The dimensionless wall permeabilities (P w*), determined by single-pass perfusion, were also site dependent. P w* was highest in the ileum [1.91 ± 0.24, (SE); n = 4], followed by the jejunum (1.64 ± 0.34; n = 4) and the colon (0.67 ± 0.38; n = 4). Based on the permeability data alone and under the assumption of no presystemic metabolism, complete bioavailability would be predicted for metkephamid. However, following oral administration, the mean absolute bioavailability was only 0.22 ± 0.065% (n = 3), indicating the overall dominance of degradation in the absorption process. Thus future strategies in oral peptide delivery should focus on increasing the stability of the peptide in the intestine by modifying the peptide structure and/or delivering the compound to an intestinal segment showing little or no enzymatic degradation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1018962415287
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  • 14
    Electronic Resource
    Electronic Resource
    Pharmacokinetics and Bioinversion of Ibuprofen Enantiomers in Humans (1994)
    Springer
    Pharmaceutical research 11 (1994), S. 824-830 
    Details
    ISSN: 1573-904X
    Keywords: ibuprofen enantiomers ; pharmacokinetics ; bioinversion ; bioavailability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract An open, randomized, six-way crossover study was conducted in 12 healthy males to assess pharmacokinetics and bioinversion of ibuprofen enantiomers. The mean plasma terminal half-life (t1/2) of R(–)ibuprofen was 1.74 hr when intravenously infused as a racemic mixture and was 1.84 hr when intravenously infused alone. The mean t1/2 of S( + )ibuprofen was 1.77 hr when dosed as S( + )ibuprofen. Examination of values of both the absorption and disposition parameters of R(–)ibuprofen revealed that the kinetics of R(–)ibuprofen were not altered by concurrent administration of S( + )ibuprofen. In this study, there was little or no presystemic inversion of R(–)ibuprofen to its S( + )isomer. Also, 69% of the intravenous dose of R(–)ibuprofen was systemically inverted and 57.6% of the oral dose of R(–)ibuprofen lysinate was bioavailable as S ( + )ibuprofen. These results indicate that the bioinversion of R(–)ibuprofen administered orally is mainly systemic. Because bioinversion of R(–)ibuprofen is not complete, S( + )ibuprofen produced higher bioavailability of S( + )ibuprofen (92.0%) than either racemic ibuprofen (70.7%) or R(–)ibuprofen (57.6%). However, bioavailability of R(–)ibuprofen (83.6%) when dosed alone was not significantly different from when dosed as racemic mixture (80.7%).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1018969506143
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  • 15
    Electronic Resource
    Electronic Resource
    Bioverfügbarkeit von Aminosäuren aus einigen industriell gefertigten proteinhaltigen Produkten (1993)
    Springer
    European journal of nutrition 32 (1993), S. 2-20 
    Details
    ISSN: 1436-6215
    Keywords: Aminosäuren ; Proteine ; proteinhaltige Produkte, Bioverfügbarkeit, Biokinetik ; Technologie ; amino acids ; proteins ; protein-containing products ; bioavailability ; biokinetics ; technology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Medicine
    Description / Table of Contents: Summary To evaluate the bioavailability of amino acids from proteins and protein-containing products, the area under the postprandial plasma-concentration-time-curve of the amino acids after oral administration needs to be calculated. Therefore, basic values depending on circadian plasma concentration rhythms have to be subtracted from measured values after loading. To determine the relative bioavailability of two tested samples, e.g., a protein-containing product before and after processing or two technologically different preparations of the same protein, it is sufficient to compare their absorption-curves, both corrected by the basic values. For that purpose the mean value-curves corresponding to the group of subjects are used, because the individual courses show considerable differences, in particular due to discontinuous gastric emptying. Enzymatic hydrolysis of a lactalbumin reduces the quantitative bioavailability of the amino acids by 12%. Concerning products used in nutrition of patients and babies, the availability from ready-to-drink liquid products is about 7–10% better than that out of the same dry products in powdered form. Compared with sterilization, ultrahigh heat treatment of milk protein products improves the availability slightly, by about 1%. Processing of dried green peas destined for use in convenience food increases the protein availability by 20%.
    Notes: Zusammenfassung Zur Bestimmung der Bioverfügbarkeit von Aminosäuren aus Proteinen und proteinhaltigen Produkten wird die Fläche unter der postprandialen Plasmakonzentrations-Zeit-Kurve der Aminosäuren nach oraler Zufuhr berechnet. Dies geschieht nach Subtraktion der durch zirkadiane Rhythmen bedingten Leerwerte von den gemessenen Plasmakonzentrationen. Zur Ermittlung der relativen Bioverfügbarkeit von zwei Testpartnern, z.B. einem proteinhaltigen Produkt vor und nach einer bestimmten Behandlung oder zwei technologisch verschiedenen Zubereitungen eines bestimmten Proteins, genügt der Vergleich der beiden bereinigten Resorptionskurven. Hierzu werden die entsprechenden Mittelwertkurven des Probandenkollektivs verwendet, da die individuellen Verlaufskurven insbesondere durch diskontinuierliche Magenentleerung erhebliche Verzerrungen aufweisen. Durch die enzymatische Hydrolyse verschlechtert sich die quantitative Bioverfügbarkeit der Aminosäuren bei einem Lactalbumin um zwölf Prozent. Bei Produkten für die Kranken- bzw. Säuglingsernährung ist die Verfügbarkeit aus fertigen Flüssigprodukten um sieben bis zehn Prozent verbessert gegenüber den gleichartigen Trockenprodukten in Pulverform. Bei ultrahocherhitzten Milcheiweißprodukten wird die Verfügbarkeit gegenüber einfach sterilisierten geringfügig um etwa ein Prozent verbessert. Durch die Präparation getrockneter grüner Erbsen für die Verwendung in Fertiggerichten wird die Verfügbarkeit des Proteins um zwanzig Prozent gesteigert.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01610081
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    Bioavailability of sorbed- and separate-phase chemicals (1993)
    Springer
    Biodegradation 4 (1993), S. 141-153 
    Details
    ISSN: 1572-9729
    Keywords: bioavailability ; biodegradation ; sorption ; oil ; soil
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Energy, Environment Protection, Nuclear Power Engineering , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00695116
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    Comparison of the effects of two different galenical preparations of glyceryl trinitrate on pulmonary artery pressure and on the finger pulse curve (1993)
    Springer
    European journal of clinical pharmacology 44 (1993), S. 451-456 
    Details
    ISSN: 1432-1041
    Keywords: Glyceryl trinitrate spray ; pharmacokinetics ; a/b-ratio ; pulmonary artery diastolic pressure ; finger pulse curve ; bioavailability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The time course and the magnitude of the effect of glyceryl trinitrate (GTN) on central venous (pulmonary artery diastolic pressure-PAPd) and peripheral arterial (a/b-ratio of the finger pulse wave) haemodynamics were compared in a randomized double-blind cross-over study in 12 patients suffering from congestive heart failure (NYHA II–III) with elevated PADd at rest (≥15 mm Hg). The data were obtained in a bioavailability study of two sprays of glyceryl trinitrate, which differed in their galenical characteristics and in the dose of GTN (0.4 mg vs. 0.8 mg). Following sublingual administration of each spray, PAPd, a/b-ratio and the plasma concentrations of GTN and its metabolites were measured up to 30 min. The relative bioavailability of GTN of the test preparation was estimated to be 157%, 161% and 147%, when calculated from the plasma concentration-time data or the integrated effect of GTN on a/b-ratio or PAPd, respectively. The mean time courses of the decrease in PAPd and the increase in the a/b-ratio of the finger pulse curve were mirror images. Thus, there was a strong correlation between the mean values of PAPd and a/b-ratio following the administration of glyceryl trinitrate. Since the slope of the relationship differed considerably between the patients, the magnitude of effect of GTN on PAPd in the individual patient could not be predicted from the changes in a/b-ratio.
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    URL: http://dx.doi.org/10.1007/BF00315542
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    Absolute bioavailability of an aqueous solution of 1-deamino-8-D-arginine vasopressin from different regions of the gastrointestinal tract in man (1993)
    Springer
    European journal of clinical pharmacology 44 (1993), S. 473-476 
    Details
    ISSN: 1432-1041
    Keywords: dDAVP ; bioavailability ; gastrointestinal tract ; healthy volunteers ; pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The absolute bioavailability of an aqueous solution of 1-deamino-8-D-arginine vasopressin (dDAVP) from different regions of the gastrointestinal (GI) tract (stomach, duodenum, jejunum, ileum, colon, rectum) has been studied in 6 healthy, male volunteers aged 24 to 35 years, followed for 12 h after each drug administration. For i. v. administration the subjects received 4 μg dDAVP. For intestinal administration 400 μg dDAVP was directly applied to six distinct sites in the GI tract via two or four channel tubes with or without a distal occlusive balloon. Biological effects were assessed and plasma and urinary levels of dDAVP were measured using a specific, sensitive RIA. Urine osmolality remained elevated and diuresis decreased for 12 h following dDAVP administration irrespective of the site of application. After i. v. administration, the half-life of elimination of dDAVP was 60.0 min, plasma clearance 1.7 ml·min−1·kg−1, amount excreted in urine 2.0 μg and renal clearance was 0.8 ml·min−1·kg−1. The mean bioavailability (f) after gastric application was 0.19% (range 0.02–0.35%). f was 0.24% after duodenal application (range 0.04–0.62%), 0.19% after jejunal (range 0.01–0.41%), 0.03% after distal ileal (range 0.01–0.08%), 0.04% after proximal colonic (range 0.01–0.12%) and 0.04% after rectal (0.01–0.10%) application. The bioavailability was significantly higher in the three upper GI regions in comparison to the three lower regions. The bioavailability of dDAVP after gastric, duodenal and jejunal application was similar to that after swallowing a tablet in a previous study. Absorption from the ileum was lower than expected and no preferential site of absorption was found.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00315546
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    Dose proportional absorption of 25–150 mg atenolol (1993)
    Springer
    European journal of clinical pharmacology 44 (1993), S. 305-306 
    Details
    ISSN: 1432-1041
    Keywords: Atenolol ; bioavailability ; intestinal absorption ; pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary We investigated the dose proportionality after the intake of oral atenolol 25, 50, 100 and 150 mg. Standard tablets were taken by 8 healthy volunteers in randomised order of doses. The area under the curve divided by dose did not differ between the doses, indicating that the absorption of this hydrophilic compound, with known incomplete bioavailability, was constant over the range tested.
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    URL: http://dx.doi.org/10.1007/BF00271380
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    Bioavailability of controlled release carbamazepine estimated by mixed effect modelling (1993)
    Springer
    European journal of clinical pharmacology 44 (1993), S. 231-235 
    Details
    ISSN: 1432-1041
    Keywords: Carbamazepine ; kinetics ; population pharmacokinetics ; bioavailability ; controlled release ; non-linear model
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The absorption properties of a conventional tablet of carbamazepine (T) and a controlled release form of carbamazepine (TCR) have been compared using a nonlinear mixed effect model (NONMEM). Plasma carbamazepine concentration data were obtained from an open, steady-state, crossover bioavailability study in which 494 measurements were obtained from 13 patients, with an equal number of samples per patient for each dosage form. The pharmacokinetic model used was a one-compartment open model with first-order absorption and elimination. The objective function was used as a measure of the goodness of fit of the model to the data. Body weight was an important determinant of carbamazepine clearance (CL) but not volume of distribution (V). Accounting for the interindividual variability in volume of distribution did not significantly influence the objective function. Including different rates of absorption (ka) for the two dosage forms resulted in a significant improvement in the objective function, as well as reducing the interindividual variability in the rate of absorption. Adding a parameter for relative bioavailability (f) of TCR improved the objective function statistically, but an unrealistic value for V was obtained, and the absorption and elimination rates appeared to be transposed in the classical “flip-flop” manner. Fixing V to the value obtained before introducing f did not change the objective function and permitted estimation of f without the confounding influence of excessive parameters. The final population parameter estimates (standard error of estimate) were: CL, 0.0522 (0.0019) l·h−1·kg−1; V, 63.7 (FIXED)l; kaT, 0.312 (0.064) h−1; kaTCR, 0.149 (0.016) h−1; f, 1.01 (0.0326); variance (additive) in CL, 0.291 (0.083) (l·h−1·kg−1)2; residual intrasubject error variance (additive), 0.572 (0.082) (mg·l−1)2. The 95% confidence interval of the extent of absorption (f) of 93.6%–107.4% was well within the generally accepted range of ±20%, while the rate of absorption of Tegretol CR was significantly slower than that of Tegretol, as expected for a controlled release product.
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    URL: http://dx.doi.org/10.1007/BF00271363
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    Comparative study of availability of prednisolone after intestinal infusion of prednisolone metasulfobenzoate and prednisone (1993)
    Springer
    European journal of clinical pharmacology 44 (1993), S. 395-399 
    Details
    ISSN: 1432-1041
    Keywords: Prednisone ; Prednisolone metasulfobenzoate ; bioavailability ; intestinal infusion ; absorption ; presystemic clearance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The role of intestinal absorption in the differential availability of prednisone (PN) and prednisolone metasulfobenzoate (PO-MS), which might account for clinical resistance to PO-MS, has been studied by an infusion technique. In a randomized cross-over design trial, a solution in isotonic saline of PN or PO-MS (115 mg·l−1 was infused at 5 ml·min−1 for 2 h, into a 25 cm segment of jejunum in 8 healthy fasting subjects. The intestinal content was partly collected and the flow rate at the end of the test segment was determined by using a water movement marker (PEG 4000). Plasma, intestinal and urine concentrations of PN and PO were determined by liquid chromatography. From the data on PO, the active molecule, the systemic availability of PO-MS was significantly smaller than of PN, with the respective mean AUCs being 1.71 and 3.60 mg·h−1. The difference was associated with smaller mean Cmax, 0.20 vs 0.64 mg·l−1, higher mean tmax, 2.94 vs 2.06 h and lower mean ka, 0.98 vs 2.18 l/h after PO-MS. No significant difference was found in the half-life or renal clearance of the formulations tested. The mean MRT was significantly increased after PO-MS, 6.82 vs 5.30 h. The observed difference probably reflected a difference in intestinal absorption. The mean absorption in the test segment of PO-MS was significantly smaller at 17.4 vs 85.5% for PN. The ester form may be a limiting factor in the intestinal absorption of PO. Therefore, the choice of PN or PO-MS should follow the therapeutic indication, depending on whether a major systemic effect or a prolonged intestinal local effect is preferred.
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    URL: http://dx.doi.org/10.1007/BF00316481
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    Kinetics of thiamin and thiamin phosphate esters in human blood, plasma and urine after 50 mg intravenously or orally (1993)
    Springer
    European journal of clinical pharmacology 44 (1993), S. 73-78 
    Details
    ISSN: 1432-1041
    Keywords: Thiamin ; thiamin monophosphate ; thiamin diphosphate ; distribution ; thiamin elimination ; bioavailability ; pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The concentrations of thiamin and thiamin monophosphate and diphosphate in plasma and whole blood samples were assessed in six healthy subjects for 12 h and in urine for 24 h following an IV and PO bolus dose of 50 mg thiamin HCl. Unphosphorylated thiamin increased rapidly in plasma after IV administration and then decreased to its initial value within 12 h in all but one subject; the half-life was 96 min. Thiamin mono and -diphosphate increased moderately (56%), and decreased slowly; the half-life of diphosphate was 664 min. Within 24 h, 53% of the administered dose was recovered in the urine, indicating a restricted distribution. After oral administration, the peak thiamin concentration in plasma was reached after 53 min and the concentration then had increased to 179% of its initial value. The elimination half-life was 154 min, and only 2.5% of the given dose was recovered in the urine. The relative bioavailability of thiamin was 5.3%. A moderate amount of the administered thiamin was stored in blood. Other body tissues must play an important part, therefore, in the distribution of thiamin.
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    URL: http://dx.doi.org/10.1007/BF00315284
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    Effect of iron deficiency anaemia and its treatment on single dose phenytoin bioavailability (1993)
    Springer
    European journal of clinical pharmacology 45 (1993), S. 387-388 
    Details
    ISSN: 1432-1041
    Keywords: Iron deficiency anaemia ; Phenytoin ; bioavailability ; pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Iron deficiency is a common nutritional deficiency, which leads to structural functional and enzymatic changes in the body that may affect the pharmacokinetics of drugs. The present study in 7 normal volunteers and 8 adult male patients with irondeficiency anaemia (IDA) was done to investigate the effect of iron deficiency and its treatment with total dose iron (TDI) on the bioavailability of a single dose of phenytoin. Phenytoin bioavailability was investigated before and 3 and 28 days after TDI. The bioavailability parameters Cmax, tmax, AUC and 2 h phenytoin concentrations were not significantly different in anaemic patients as compared to normal volunteers before or after treatment, except for an increase in tmax 28 days after TDI treatment.
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    URL: http://dx.doi.org/10.1007/BF00265961
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    Pharmacokinetics of pantoprazole following single intravenous and oral administration to healthy male subjects (1993)
    Springer
    European journal of clinical pharmacology 44 (1993), S. 575-578 
    Details
    ISSN: 1432-1041
    Keywords: Pantoprazole ; pharmacokinetics ; bioavailability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The plasma pharmacokinetics of pantoprazole have been investigated following single intravenous infusion and single oral administration at a dose of 40 mg to 12 healthy male subjects in a randomised cross-over study. Both treatments were generally well tolerated and no relevant compound-related adverse events were noted. The plasma pharmacokinetics of pantoprazole following intravenous infusion in this group of subjects were characterised by a total plasma clearance of 0.13 l·h−1·kg−1 and apparent terminal elimination half-life 1.9 h. The apparent volume of distribution estimated at steady state (0.171·kg−1) was compatible with the localization of a major fraction of the compound in extracellular water. Following oral administration as an enteric-coated tablet formulation, a variable onset of absorption was followed by rapid attainment of maximum plasma concentrations of pantoprazole. Pantoprazole was well absorbed following oral administration; the absolute systemic bioavailability of the compound was estimated as 77% (95% CI, 67 to 89%).
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    URL: http://dx.doi.org/10.1007/BF02440862
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    On the bioavailability of 2-chloro-2′-deoxyadenosine (CdA) (1993)
    Springer
    European journal of clinical pharmacology 44 (1993), S. 579-582 
    Details
    ISSN: 1432-1041
    Keywords: 2-Chloro-2′-deoxyadenosine (CdA) ; omeprazole ; food ; pharmacokinetics ; bioavailability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The pharmacokinetics of oral CdA (0.24 mg/kg) was studied in 4 patients (1 with hairy cell leukaemia and 3 with B-cell chronic lymphocytic leukaemia) to determine any effect of food and fasting with and without omeprazole. Food intake did not significantly influence the bioavailability of CdA (42% after food intake vs 46% while fasting) but it did reduce the maximum plasma concentration (Cmax) by 40%; 83 compared to 116 nM while fasting. The time to reach maximum concentration (tmax) was delayed about 0.8 h after food intake. Pretreatment with omeprazole did not significantly influence the bioavailability of CdA (51% vs 46% without), or the interindividual variability in bioavailability in the fasting state (C.V. 0.26 with and C.V. 0.27 without). In conclusion, there was a small, though not statistically significant reduction in the bioavailability of CdA after food intake. Omeprazole did not significantly improve the bioavailability of CdA.
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    URL: http://dx.doi.org/10.1007/BF02440863
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    Pharmacokinetics of oral tiopronin (1993)
    Springer
    European journal of clinical pharmacology 45 (1993), S. 79-84 
    Details
    ISSN: 1432-1041
    Keywords: Tiopronin ; 2-Mercaptopropionylglycine ; bioavailability ; urinary excretion ; cystine urolithiasis ; pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Ten healthy subjects were given 500 mg (3064 μmol) tiopronin, or 2-mercaptopropionylglycine (2-MPG) by mouth. Cmax was reached after 3–6 h, and after a shorter β-phase a long terminal half-life of 53 h of total tiopronin was found. Tiopronin measured as unbound (non-protein-bound) drug disappeared more rapidly from plasma, with a calculated t 1/2 of 1.8 h. Mean residence time was higher (58 h) when calculated as total tiopronin than as unbound tiopronin (6 h), and this was also the case for the volume of distribution (Vλ=4551 vs Vλ,u=41 1). The results indicate extensive protein binding in plasma and a deep pool of tissue bound tiopronin after the first absorption and distribution phases. Absolute bioavailability (f) was 63%, and bioavailability calculated from urinary excretion was 47%, which are well correlated with each other. Urinary excretion was mainly confined to the first 6 h (74%) and was almost complete (98%) within 12 h. We conclude that the maximal absorption of the tiopronin was late, protein and tissue binding of the drug were high and its bioavailability varied. The renal excretion of low molecular weight tiopronin occurred early, which implies that the drug should be given in divided doses, at least twice daily, for optimal efficiency in the treatment of cystinuria.
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    Pharmacokinetics and β-blocking effects of transdermal timolol (1993)
    Springer
    European journal of clinical pharmacology 44 (1993), S. 493-495 
    Details
    ISSN: 1432-1041
    Keywords: Timolol ; β-adrenoceptor antagonist ; transdermal ; percutaneous absorption ; skin ; pharmacokinetics ; bioavailability ; adverse effects
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The pharmacokinetic profiles of transdermal timolol 6 and 24 mg (as 5 and 20% w/v patches) was studied in four healthy young volunteers. To assess its bioavailability, the pharmacokinetics of an IV infusion of timolol maleate 5 mg was also determined in the same subjects. When the 20% (w/v) timolol patch was applied, the mean bioavailability was 74.4%. Plasma timolol concentrations were below the detection limit when a 5% patch was applied to the same skin area in all four subjects, except for one in whom the bioavailability was 23.6%. Weak erythema developed at the application site in all of the volunteers after application of the 20% (w/v) patch. However, erythema did not develop in any volunteer when the 5% patch was applied. The β-blocking effect was determined by exercise testing. Similar plasma levels generated similar changes in exercise-induced heart rate after the transdermal and intravenous administration of timolol.
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    URL: http://dx.doi.org/10.1007/BF00315551
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    Single dose pharmacokinetics of fenspiride hydrochloride: phase I clinical trial (1993)
    Springer
    European journal of clinical pharmacology 45 (1993), S. 169-172 
    Details
    ISSN: 1432-1041
    Keywords: Fenspiride ; pharmacokinetics ; bioavailability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The absolute bioavailability of fenspiride has been studied in twelve healthy volunteers. It was administered IV and orally in single doses of 80 mg fenspiride hydrochloride according to a randomised crossover pattern. Following IV administration, the plasma clearance of fenspiride was about 184 ml·min−1, and its apparent volume of distribution was moderately large (2151). When given orally as a tablet, fenspiride exhibited fairly slow ab- sorption; the maximum plasma concentration (206 ng·ml−1) was achieved 6 h after administration. The absolute bioavailability was almost complete (90%). The tablet had slow release characteristics. The elimination half-life obtained from the plasma data was 14 to 16 h independent of the route of administration.
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    Use ofEnteromorpha intestinalis (Chlorophyceae) for active biomonitoring of heavy metals in the weser estuary (1993)
    Springer
    Aquatic ecology 27 (1993), S. 189-195 
    Details
    ISSN: 1573-5125
    Keywords: heavy metals ; biomonitoring ; bioavailability ; Enteromorpha intestinalis ; Weser estuary
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The present study was planned to assess the validity ofEnteromorpha intestinalis for an active biomonitoring of heavy metals in the Weser estuary. Exposure of cultured algae (active biomonitoring) was carried out in 1987 and 1988, simultaneouslyEnteromorpha spp. was collected from the banks (passive monitoring) in the estuary. Cd, Pb, Ni, Zn and Cu contents of exposed algae were higher than the metal content of collected algae. Metal contents of both collected and field algae varied significantly over space and time. Bioconcentration factors and results of linear regression analysis indicate, that the bioavailability of Cu and Ni varies with regard to the sampling location but cannot be calculated from heavy metal concentration in the water. Due to the different metal and species specific bioavailability, we want to stress the need to monitor contamination of organisms directly. An active biomonitoring usingE. intestinalis will establish a rationale to compare contamination of different estuaries.
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    URL: http://dx.doi.org/10.1007/BF02334782
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    Application of a simplified method to determine bioavailability of an oral dose of phenytoin (1993)
    Springer
    Journal of pharmacokinetics and pharmacodynamics 21 (1993), S. 195-208 
    Details
    ISSN: 1573-8744
    Keywords: bioavailability ; phenytoin ; Michaelis-Menten kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The bioavailability of capsules of phenytoin was determined by two methods: a method involving the numerical integration of the Michaelis-Menten equation and an alternative method involving fitting the time course of plasma concentrations, following the administration of the reference intravenous dosage, to an empirical quadratic function of time. The latter procedure requires much simpler computations. The two methods yielded very similar estimates of the rate and extent of absorption of phenytoin. Total absorption was 0.90±0.05 and 0.89±0.05(x±SE, n=6)using the methods of numerical integration and quadratic curve fitting, respectively. Both methods indicated that the rate of absorption of phenytoin was inconsistent and slow. Half the total absorption of phenytoin occurred over 2.5 ±0.3 hr but the remainder was absorbed very slowly over a period of about 30 hr. Empirical functions may be more generally useful in the determinations of the bioavalability of drugs, particularly if some aspects of the disposition are saturable.
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    Correlation Between the Disintegration Time and the Bioavailability of Vitamin C Tablets (1993)
    Springer
    Pharmaceutical research 10 (1993), S. 239-242 
    Details
    ISSN: 1573-904X
    Keywords: vitamin C ; ascorbic acid ; disintegration ; dissolution ; bioavailability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The goal of this study was to examine if the current USP disintegration standard for vitamin C tablets (max. 30 min in water at 37°C with disks) is adequate or if a tighter disintegration standard (e.g., European compendia max. 15 min) should be recommended based on bioavailability considerations. Four formulations of 500-mg vitamin C tablets ranging in mean disintegration time from 9 to 120 min were compared with a standard vitamin C solution in a double-blind clinical trial with 15 subjects. The products were administered with a standard breakfast. The data show that a solution of vitamin C and a fast-disintegrating tablet (8–9 min) have equal but significantly lower bioavailability than tablets with longer disintegration times (30, 60, 120 min). Tablets with a mean disintegration time of 60 min showed the highest bioavailability. When the disintegration test was performed without disks, disintegration times increased so much that only the tablets with the fastest disintegration time (which were also the tablets with the lowest bioavailability) met the current USP disintegration time limit. Based on the results of the study, changes in the USP standard to omit the disks or to shorten the disintegration time will not achieve enhanced bioavailability but will result in reduced vitamin C absorption. In vitro dissolution of vitamin C tablets did not show the traditional relationship with bioavailability.
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    URL: http://dx.doi.org/10.1023/A:1018938911420
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    Evidence for an Interaction Between the β-Blocker Pafenolol and Bile Salts in the Intestinal Lumen of the Rat Leading to Dose-Dependent Oral Absorption and Double Peaks in the Plasma Concentration–Time Profile (1993)
    Springer
    Pharmaceutical research 10 (1993), S. 879-883 
    Details
    ISSN: 1573-904X
    Keywords: pharmacokinetics ; oral absorption ; double peaks ; absorption interaction ; intestinal excretion ; bioavailability ; dose dependency
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Pafenolol is a β-blocker with unusual oral absorption properties. The blood concentration–time profile exhibits two peaks, and the bioavailability is low and dose dependent because of incomplete and nonlinear intestinal uptake. We addressed the question whether the intestinal absorption of pafenolol was affected by bile depletion in the gut lumen of rats. Further, the hypothesis that variable gastric emptying accounts for double peaks in blood was tested by duodenal administration of pafenolol. Following intraduodenal administration to rats with intact bile secretion, double peaks were observed in the blood concentration–time curve. The bioavailability was 6.8 ± 0.7% for the low dose (1 µmol/kg) and increased significantly to 28 ± 10% following the high duodenal dose (25 µmol/kg). These blood concentration–time profiles exclude interrupted gastric emptying as cause of the twin peaks. In bile duct-cannulated rats the intestinal absorption of the low dose (1 µmol/kg) was still poor (F = 10.7 ± 5.5%) and the blood concentration–time profile contained two peaks. Following administration of a high duodenal dose (25 µmol/kg) to rats with an almost bile-free small intestine, the absorption rate increased and the double-peak phenomenon disappeared in five of seven rats, while the bioavailability increased significantly, to 62 ± 27%. These results suggest that the low bioavailability of pafenolol is due to a complexation between bile and pafenolol in the gut lumen, preventing intestinal uptake in the major part of the small intestine. Further, such complex formation in the intestinal lumen may be the underlying mechanism of the double peaks observed in the blood concentration–time profile.
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    In Vivo/in Vitro Correlation of Experimental Sustained-Release Theophylline Formulations (1993)
    Springer
    Pharmaceutical research 10 (1993), S. 588-592 
    Details
    ISSN: 1573-904X
    Keywords: theophylline ; sustained release ; bioavailability ; deconvolution ; in vivo/in vitro correlation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A novel multiparticulate sustained-release theophylline formulation, which consisted of spherical drug pellets coated with a rate-controlling membrane, was evaluated in vivo. Two preparations that differ solely in the coat thickness, and hence rate of in vitro drug release, were studied in comparison with a solution of the drug. Both preparations produced serum concentration profiles that are reflective of a slow and sustained rate of absorption. The in vivo release versus time profiles calculated using a deconvolution procedure showed that the two preparations differed in the rate but not the extent of drug release. Satisfactory correlation was also obtained between the in vivo and the in vitro results. When the two preparations were further compared using the parameters, time to reach peak concentration (T p), peak concentration (C p), and total area under the serum concentration versus time curves (AUC), a statistically significant difference was observed in the T p and C p values but not the AUC values, suggesting that the preparations differed in the rate but not the extent of absorption. In addition, the extent of absorption from both preparations was comparable to that obtained with the drug solution.
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    Clinical Pharmacokinetics and Relative Bioavailability of Oral Procaterol (1993)
    Springer
    Pharmaceutical research 10 (1993), S. 603-605 
    Details
    ISSN: 1573-904X
    Keywords: procaterol ; bronchodilator ; healthy volunteers ; pharmacokinetics ; bioavailability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The pharmacokinetics and relative oral bioavailability of procaterol, an orally active β2-adrenergic agonist bronchodilator were evaluated in healthy volunteers. Procaterol was rapidly absorbed after oral administration. Mean plasma procaterol concentration–time profiles and pharmacokinetic parameters for both formulations were essentially superimposable. Following tablet administration, the mean C max was 358 pg/mL and the corresponding mean t max was 1.6 hr. Mean renal clearance was 163 mL/min and accounted for approximately one-sixth of the mean apparent oral plasma clearance (988 mL/min). The mean apparent elimination half-life of procaterol was 4.2 hr. Hepatic metabolism appears to be the primary mechanism for elimination of procaterol from the body, and first-pass metabolism may limit systemic bioavailability.
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    URL: http://dx.doi.org/10.1023/A:1018966506819
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  • 35
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    In Vivo Validation of the Release Rate and Palatability of Remoxipride-Modified Release Suspension (1993)
    Springer
    Pharmaceutical research 10 (1993), S. 1020-1026 
    Details
    ISSN: 1573-904X
    Keywords: remoxipride ; modified release ; suspension ; bioavailability ; convolution ; deconvolution ; dissolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Remoxipride, a D2-dopamine receptor antagonist, is well tolerated and completely absorbed after oral administration. Because of its extremely bitter taste, an oral palatable suspension was developed by using a taste-masking microencapsulation. The bioavailability of remoxipride was investigated in two studies in healthy volunteers after administration of a 100-mg dose in suspension. The first study used a capsule as reference, and the second study a plain solution. Taste assessment was carried out in the second study. The extent of bioavailability was the same when comparing the oral suspension to a capsule and to a plain solution. However, the rate of absorption is delayed, and Tmax was 3.0 hr after the suspension, 1.0 hr after the oral solution, and 1.6 hr after the capsule. The release rate in vitro from the suspension was determined by applying the USP-paddle method. By using numerical convolution and deconvolution, the release rates in vivo and in vitro were shown to be similar when using water with 0.5% sodium lauryl sulfate as dissolution liquid. The taste-masked oral suspension is suitable for full-scale production, with good control of the encapsulation process and of the preparation of a suspension.
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    URL: http://dx.doi.org/10.1023/A:1018966823600
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  • 36
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    Effect of Sodium Acid Pyrophosphate on Ranitidine Bioavailability and Gastrointestinal Transit Time (1993)
    Springer
    Pharmaceutical research 10 (1993), S. 1027-1030 
    Details
    ISSN: 1573-904X
    Keywords: ranitidine ; effervescent tablet ; absorption ; bioavailability ; bioequivalence ; sodium acid pyrophosphate ; gastrointestinal transit time
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract During development of a ranitidine effervescent oral solution dosage form, a marked decrease was observed in the extent of ranitidine absorption relative to the conventional oral tablet. Two studies were conducted in healthy volunteers to confirm the involvement of an excipient, SAPP (sodium acid pyrophosphate), and the mechanism of interaction, altered gastrointestinal transit. The first study (n = 12) involved single-dose crossover comparisons of (A) 150 mg ranitidine with 1132 mg SAPP versus (B) 150 mg ranitidine and (C) 150 mg ranitidine with all the effervescent tablet excipients except SAPP versus (D) a 150-mg ranitidine effervescent tablet, all administered as oral solutions. Serum ranitidine AUC, C max, and t max were compared using two one-sided t test 90% confidence intervals (CI). Comparing treatments A to B and D to C, all 90% CI were below the 80–120% range, indicating significantly less extensive ranitidine absorption (54% based on AUC) from the oral solutions containing SAPP. The second study (n = 12) was a single-dose crossover comparing 50 µCi 111InCl solutions with and without 1132 mg SAPP. Gastrointestinal transit times, determined by scintigraphic imaging, were compared between treatments. Gastric emptying time was unchanged, but small intestinal transit time was decreased to 56% in the presence of SAPP. More rapid small intestinal transit associated with an excipient of a solution dosage form apparently resulted in a decreased extent of ranitidine absorption. This observation contradicts the conventional wisdom that oral solutions are unlikely to fall short of bioequivalence relative to solid oral formulations.
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    URL: http://dx.doi.org/10.1023/A:1018918907670
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    Biopharmaceutics of Didanosine in Humans and in a Model for Acid-Labile Drugs, the Pentagastrin-Pretreated Dog (1993)
    Springer
    Pharmaceutical research 10 (1993), S. 1157-1164 
    Details
    ISSN: 1573-904X
    Keywords: didanosine ; pentagastrin-pretreated dog ; formulation development ; bioavailability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Didanosine is a purine nucleoside analogue approved for the treatment of human immunodeficiency virus infection. It is extremely unstable at pH values less than 3 and requires protection against gastric acid-induced hydrolysis. Beagle dogs pretreated with pentagastrin, an analogue of gastrin that reproducibly stimulates gastric acid secretion, have been used to screen different didanosine formulations. The absolute bioavailability of didanosine from a saline solution decreased from approximately 43% in untreated dogs to 8% after pretreatment with pentagastrin. Administration of buffered solution of didanosine to untreated and pretreated dogs yielded bio-availability estimates of 37 and 30%, respectively. In humans, the bioavailability from a similar buffered solution was approximately 40%. Pentagastrin-pretreated dogs were used to evaluate four new products relative to a citrate-phosphate buffer sachet, the formulation selected for large-scale clinical trials in humans. Two of these new formulations, a chewable tablet and an antacid suspension, were more bioavailable then the reference sachet. This also proved to be true in man, necessitating an adjustment in the dose of didanosine when administered as the chewable tablet. Dogs pretreated with pentagastrin accurately predicted the improved bioavailability of new didanosine formulations prior to clinical use. This animal model may be helpful in evaluating the biopharmaceutics of other acid-labile drugs.
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    URL: http://dx.doi.org/10.1023/A:1018964117665
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    A Floating Controlled-Release Drug Delivery System: In Vitro-in Vivo Evaluation (1993)
    Springer
    Pharmaceutical research 10 (1993), S. 1321-1325 
    Details
    ISSN: 1573-904X
    Keywords: floating ; controlled release ; theophylline ; gastric retention time ; bioavailability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A novel floating controlled-release drug delivery system was formulated in an effort increase the gastric retention time of the dosage form and to control drug release. The buoyancy was attributed to air and oil entrapped in the agar gel network. A floating controlled-release 300-mg theophylline tablet having a density of 0.67 was prepared and compared in vitro and in vivo to Theo-dur. The in vitro release rate of the floating tablet was slower. In vivo scintigraphic studies for a floating and a heavy nonfloating tablet, under fasting and nonfasting conditions, showed that the presence of food significantly increased the gastric retention time for both tablets, and tablet density did not appear to make a difference in the gastric retention time. However, the positions of the floating and nonfloating tablets in the stomach were very different. Bioavailability studies in human volunteers under both fasting and nonfasting conditions showed results comparable to those with Theo-dur. The floating controlled-release theophylline tablet maintained constant theophylline levels of about 2 mg/mL for 24 hr, which may be attributable to the release from the agar gel matrix and the buoyancy of the tablet in the stomach.
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    URL: http://dx.doi.org/10.1023/A:1018921830385
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  • 39
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    The effect of phytase on the availability of P from myo-inositol hexaphosphate (phytate) for maize roots (1993)
    Springer
    Plant and soil 154 (1993), S. 189-196 
    Details
    ISSN: 1573-5036
    Keywords: bioavailability ; maize ; myo-inositol ; phosphorus ; phytase ; phytin ; soil
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The effect of adding phytase to the root medium of maize plants on the P-availability of added myo-inositol hexaphosphate (phytin) has been studied in pot experiments. When 40 mM phytin-P in nutrient solution was incubated in quartz-sand for 15 days in the absence of plants, 80% of it could be recovered from the solution as soluble organic P. Maize plants growing on this mixture assimilated P from phytin at rates comparable to those from inorganic phosphate (Pi). At a lower addition rate (2 mM phytin-P) only 10% was recovered in the soil solution, and plant growth was severely limited by P. At this low phytin level, the addition of phytase (10 enzyme units per kg sand) increased the plants' dry weight yield by 32%. The relative increases of the Pi concentration in the solution and of the amount of P in the plants were even higher, indicating that the observed growth stimulation was due to an increased rate of phytin hydrolysis. The enzyme-induced growth stimulation was also observed with plants growing in pots filled with soil low in P, when phytin was added. However, on three different soils the addition rates of phytin and phytase necessary for obtaining a significant phytase effect were both about 10 times higher than those required in quartzsand. It is concluded that the P-availability from organic sources can be limited by the rate of their hydrolytic cleavage.
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    URL: http://dx.doi.org/10.1007/BF00012524
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    Bio-availability of phosphorus in sediments of the western Dutch Wadden Sea (1993)
    Springer
    Hydrobiologia 253 (1993), S. 151-163 
    Details
    ISSN: 1573-5117
    Keywords: Wadden Sea ; sediments ; phosphorus compounds ; bioavailability ; algae ; iron ; calcium redox potential ; oxygen
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The purpose of this study was to make a prognosis of the effects of extended purification of terrestrial waste water, reaching the Wadden Sea by the River Rhine and Lake IJssel, on the phosphate concentration in the western Wadden Sea. The quantities of different phosphorus fractions in intertidal and subtidal sediments of the Marsdiep tidal basin (western Dutch Wadden Sea) were measured. Different methods are applied to determine the amount of phosphorus that can be released from these sediments. The direct bioavailability is determined by inoculating sediment suspensions with a natural mixture of precultured micro-organisms from the sampling area. A second approach is the measurement of the phosphate release under different redox conditions. Sequential extraction of sediment samples with different solvents is also applied. Under the present conditions and compared to the nutrient loads from fresh water (Lake IJssel) and from the North Sea, the phosphorus stored in the sediments of the western Dutch Wadden Sea plays a minor role in the total supply to micro-algae and bacteria. The bulk of the biologically available phosphorus in the sediments originates from the metal-associated fraction. Releasable phosphate may contribute to the local annual primary production to an extent of ca 45 to ca 150 g C m−2 a−1. The total amount of phosphorus in the sediment (mainly calcite associated) is twice to 6 times the biologically available amount.
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    URL: http://dx.doi.org/10.1007/BF00050735
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    Seasonal variation of acid volatile sulfide concentration in sediment cores from three northeastern Minnesota lakes (1993)
    Springer
    Hydrobiologia 271 (1993), S. 87-95 
    Details
    ISSN: 1573-5117
    Keywords: acid volatile sulfide ; metal ; bioavailability ; sediment ; freshwater ; temperature ; seasonal
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Acid volatile sulfide (AVS) is a natural agent in sediments which complexes some cationic metals and thereby influences the toxicity of these metals to benthic organisms. Because of its influence on metal bioavailability, AVS has been proposed as a key normalization phase for the development of sediment quality criteria for metals. However, studies conducted primarily in marine and estuarine systems have shown that AVS concentrations can vary markedly both temporally and with (sediment) depth. In this study, AVS concentrations were measured monthly for 16 mo in several segments of sediment cores from three freshwater lakes: Caribou Lake, Fish Lake and Pike Lake in northeastern Minnesota, USA. The concentrations of AVS in cores from the three lakes varied inversely with sediment depth. AVS concentrations also varied seasonally by as much as two orders of magnitude and were directly correlated with changes in water temperature. The correlation between AVS and temperature likely was related both to changes in primary productivity and sediment microbial activity.
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    Molecular diagnostics of polycyclic aromatic hydrocarbon biodegradation in manufactured gas plant soils (1993)
    Springer
    Biodegradation 4 (1993), S. 303-321 
    Details
    ISSN: 1572-9729
    Keywords: bioavailability ; bioluminescence ; gene probe ; in situ microbial analysis ; mRNA ; polynuclear aromatic hydrocarbons
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Energy, Environment Protection, Nuclear Power Engineering , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Traditional methods for quantifying specific catabolic bacterial populations underestimate the true population count due to the limitations of the necessary laboratory cultivation methods. Likewise,in situ activity is also difficult to assess in the laboratory without altering the sample environment. To circumvent these problems and achieve a truein situ bacterial population count and activity measurement, new methods based on molecular biological analysis of bacterial nucleic acids were applied to soils heavily contaminated with polycyclic aromatic hydrocarbons (PAH). In addition, a naphthalene-lux reporter system was used to determine bioavailability of naphthalene within these soils. DNA extracted from seven PAH-contaminated soils and hybridized with thenahA gene probe indicated that the naphthalene degradative genes were present in all samples in the range of 0.06 to 0.95 ng/100 µl DNA extract which was calculated to represent 3.2×106 to 1.1×1010 cells/g soil (assuming one copy of these genes per cell).14C-naphthalene mineralization was observed in all contaminated soils with14CO2 mineralization rates ranging from 3.2×10−5 to 304,920.0×10−5 µg g soil−1h−1. Phenanthrene, anthracene, and benzo(a)pyrene were mineralized also in several soils. Messenger RNA transcripts ofnahA were isolated and quantified from 4 soils. Only one soil tested, soil B, was inducible with salicylate above thein situ nahA gene transcript level. Two of the soils, C and G, were already fully inducedin situ. The naphthalene mineralization rate correlated positively with the amount ofnahA gene transcripts present (r=0.99). Naphthalene was bioavailable in soils A, D, E, G, and N as determined by a bioluminescent response from the naphthalene-lux reporter system. Taken together, these data provided information on what the naphthalene-degrading bacterial population was experiencingin situ and what approaches would be necessary to increase activity.
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    Regional Gastrointestinal Absorption of the Beta-Blocker Pafenolol in the Rat and Intestinal Transit Rate Determined by Movement of 14C-Polyethylene Glycol (PEG) 4000 (1993)
    Springer
    Pharmaceutical research 10 (1993), S. 130-135 
    Details
    ISSN: 1573-904X
    Keywords: pharmacokinetics ; oral absorption ; intestinal permeability ; bioavailability ; double-peaks ; dose dependency
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The gastrointestinal absorption characteristics of pafenolol following oral administration as a solution in man and rat has previously been found to be a double-peak phenomenon and exhibited dose-dependent bioavailability, despite negligible presystemic metabolism. In both man and rat the first peak appeared approximately 0.5–1 hr postdose and the second, more pronounced peak 3–4 hr postdose. In rat more than 90% of the available dose was absorbed during the second peak. In the present study we investigated the absorption of a solution of pafenolol in rats after intrajejunal and intraileal administration. The resulting blood concentration–time profile of pafenolol exhibited one peak only; the extent of absorption was similar to that observed when the same dose was given orally. The small intestinal transit time of the 14C-PEG 4000 solution was found to be more than 3 hr. The transit rate was higher in the proximal part of the small intestine compared to the more distal part, where the transit of the solution was staggered. In conclusion, the results of the intestinal transit time investigation and the administrations of pafenolol at different levels of the alimentary tract indicate that pafenolol is a drug with a specific absorption site located in the ileocolonic region.
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    The Effect of Gastric pH on the Absorption of Controlled-Release Theophylline Dosage Forms in Humans (1993)
    Springer
    Pharmaceutical research 10 (1993), S. 1037-1045 
    Details
    ISSN: 1573-904X
    Keywords: controlled-release theophylline ; pH-dependent dissolution ; achlorhydric humans ; bioavailability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The bioavailability of three marketed controlled-release dosage forms and a reference solution of theophylline was studied in eight subjects with normal gastric fluid acidity and seven subjects who were achlorhydric. Gastric pH was monitored with a Heidelberg capsule. One of the controlled-release dosage forms dissolved more rapidly in vitro when exposed to acid conditions, one dissolved more rapidly in pH 7.5 media, and the third dissolved at a rate independent of pH. Using a crossover design, each subject received each dosage form twice. Blood was sampled for up to 47 hr after each dose, and serum was assayed for theophylline by HPLC. The product which dissolved more rapidly under acid conditions in vitro exhibited a 3 hr longer T max in the achlorhydrics compared to the normal subjects. The product which dissolved more rapidly in the pH 7.5 media exhibited a relatively higher AUC(0–∞) in the achlorhydric subjects than in normal subjects after the AUC data were normalized for clearance differences between the two subject groups. The in vivo bioavailability of these dosage forms could be related to the in vitro dissolution characteristics for some parameters. However, with the exception of the mean T max values, the mean bioavailability parameters differed by less than 20% between the two subject groups.
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    Intranasal Absorption of a Kappa Agonist Analgesic (1993)
    Springer
    Pharmaceutical research 10 (1993), S. 1083-1086 
    Details
    ISSN: 1573-904X
    Keywords: kappa agonist analgesic ; nasal absorption ; bioavailability ; pharmacokinetics ; ED50.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
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    URL: http://dx.doi.org/10.1023/A:1018987328143
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  • 46
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    Gelatin-Acacia Microcapsules for Trapping Micro Oil Droplets Containing Lipophilic Drugs and Ready Disintegration in the Gastrointestinal Tract (1993)
    Springer
    Pharmaceutical research 10 (1993), S. 1115-1122 
    Details
    ISSN: 1573-904X
    Keywords: nonhardened gelatin–acacia microcapsules ; complex coacervation ; bioavailability ; lipophilic drugs ; O/W emulsions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Nonhardened gelatin-acacia microcapsules were studied for encapsulation of microdroplets of oil solution containing a lipophilic drug as core material and ready disintegration with release of micro oil droplets in the gastrointestinal tract. Probucol and S-312-d, a Ca-channel blocker, were employed as model lipophilic drugs. Glyceryl tricaprylate and tricaprate mixture solutions containing these drugs were encapsulated according to the complex coacervation method and were recovered as free-flowing powders without any hardening (cross-linking) step. The microcapsules obtained were disintegrated, and the emulsion was reproduced within 3 min at 37°C in the first or second test solution defined in the Japanese Pharmacopeia XII. When the microcapsules were stored as a powder at room temperature in a closed bottle, no significant change in their appearance or disintegration time upon rehydration was observed even after 1 year. Oral bioavailabilities of model drugs from the microcapsules were tested in rats and dogs and compared with those from other conventional formulations. Gastrointestinal absorption of both probucol and S-312-d from the microcapsules was remarkably more efficient than that from other formulations such as powders, granules, or oil solution. The proposed method for microencapsulation could be useful for powdering drug-containing oil solutions or O/W emulsions while maintaining excellent bioavailability.
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    URL: http://dx.doi.org/10.1023/A:1018951814939
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    Synthesis and Evaluation of Morpholinoalkyl Ester Prodrugs of Indomethacin and Naproxen (1993)
    Springer
    Pharmaceutical research 10 (1993), S. 1191-1199 
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    ISSN: 1573-904X
    Keywords: indomethacin ; naproxen ; prodrugs ; hydrolysis kinetics ; solubility ; partition coefficient ; ulcerogenicity ; bioavailability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Morpholinoalkyl esters (HC1 salts) of naproxen 1 and indomethacin 3 were synthesized and evaluated in vitro and in vivo for their potential use as prodrugs for oral delivery. Prodrugs were freely soluble in simulated gastric fluid (SGF) and pH 7.4 phosphate buffer and showed a minimum of a 2000-fold increase in solubility over the parent drugs. All prodrugs were more lipophilic than parent drugs as indicated by n-octanol/pH 7.4 buffer partition coefficients but less lipophilic in terms of n-octanol/SGF partition coefficients. Potentiometrically determined pK a's for prodrugs were in the range of 6.89 to 8.62 at 25°C. All prodrugs were quantitatively hydrolyzed to their respective parent drugs by enzymatic and/or by chemical means. An increase in carbon chain length rendered the prodrugs more stable at pH 7.4 but less stable in SGF. The esters were generally found to be hydrolyzed rapidly in rat plasma at 37°C, the half-lives being in the range of 1.2–31.0 min. Based on in vitro results, prodrugs 2c and 4c were chosen to evaluate solid-state stability, in vivo bioavailability, and ulcerogenicity. At elevated temperatures, the solid-state decomposition of 2c and 4c followed biphasic kinetics, with rapid decomposition occurring initially. The prodrugs were 30–36% more bioavailable orally than the parent drugs following a single equimolar solution dose in rats. Prodrugs 2c and 4c were significantly less irritating to gastric mucosa than parent drugs following single-dose and chronic oral administration in rats.
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    URL: http://dx.doi.org/10.1023/A:1018976520391
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    The Dissolution and Bioavailability of Etodolac from Capsules Exposed to Conditions of High Relative Humidity and Temperatures (1993)
    Springer
    Pharmaceutical research 10 (1993), S. 1295-1300 
    Details
    ISSN: 1573-904X
    Keywords: dissolution ; bioavailability ; etodolac capsules ; stressed conditions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The dissolution and bioavailability of etodolac from capsules exposed to high relative humidity and temperature were compared to those from capsules stored at room temperature (RT). Dissolution of stressed and control capsules was evaluated using a USP basket apparatus at 100 rpm with 900 mL pH 7.5 phosphate buffer (0.05 M) at 37°C. The dissolution of etodolac from capsules exposed to stressed conditions was also evaluated with enzymes (pancreatin, 1%, w/v) added to the dissolution medium. The bioavailability of etodolac from capsules exposed to stressed conditions was compared in both dogs and humans to capsules stored at RT conditions. Capsules, 200 and 300 mg, exposed to stressed conditions failed the dissolution (without enzymes) specification [not less than 85% released (80% Q) in 30 min]. However, upon enzyme addition, all capsules met the specification. The rate and extent of absorption from these 200 and 300 mg etodolac capsules in dogs were equivalent to those from capsules stored at RT conditions that passed the dissolution specification. Similarly, the bioavailability of etodolac from 300 mg capsules that failed the dissolution specification upon exposure to stressed conditions was equivalent to that of control capsules in 24 adult male volunteers. Thus, an in vitro dissolution test with enzymes provides a better indication of stressed capsule performance in vivo.
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    URL: http://dx.doi.org/10.1023/A:1018913628568
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    Absorption of Recombinant Human Granulocyte Colony-Stimulating Factor (rhG-CSF) from Rat Nasal Mucosa (1993)
    Springer
    Pharmaceutical research 10 (1993), S. 1372-1377 
    Details
    ISSN: 1573-904X
    Keywords: granulocyte colony-stimulating factor (rhG-CSF) ; recombinant human granulocyte-CSF ; nasal absorption in rats ; bioavailability ; leukocyte number
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Nasal absorption of recombinant human granulocyte colony-stimulating factor (rhG-CSF) was examined in the rat. The relative bioavailability of rhG-CSF for subcutaneous administration was ∼2%, as evaluated from the immunologically active rhG-CSF concentration in rat plasma and the area under the curve (AUC) of the plasma rhG-CSF concentration versus time for 8 hr. Pharmacological availability relative to subcutaneous administration was determined from the increase in total blood leukocyte numbers. The pharmacological availability was 5–10%, determined from the AUC for the increased ratio of total leukocyte numbers versus time for 48 hr; it was slightly dependent on the pH and the osmotic pressure of the dosing solution. Accordingly, the plasma concentration of rhG-CSF did not always reflect its pharmacological effects. Relative bioavailability and pharmacological availability were increased about 23 times and 3 times, respectively, by polyoxyethylene 9-lauryl ether (Laureth-9), but no increase in availability occurred with sodium glycocholate. The increase in total leukocyte numbers was maintained during multiple rhG-CSF dosing, and the addition of Laureth-9 further increased the pharmacological effects of this agent. This study indicates that nasal administration of rhG-CSF is an effective parenteral administration route.
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    URL: http://dx.doi.org/10.1023/A:1018990318090
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    Speciation of antimony by atomic absorption spectrometry. Applicability to selective determination of Sb(III) and Sb(V) in liquid samples and of bioavailable antimony in sediments and soil samples (1992)
    Springer
    Microchimica acta 109 (1992), S. 149-155 
    Details
    ISSN: 1436-5073
    Keywords: Sb(III) ; Sb(V) ; bioavailability ; sediments ; water
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A comparative study was made of several methods to speciale Sb(III) and Sb(V) by AAS: 1) Selective extraction of Sb(III) with lactic acid/malachite green graphite furnace-AAS, 2) Sb(III) and total antimony determination by hydride generation-AAS coupled to flow injection, batch, and continuous flow systems. These methods were applied to determine total antimony and Sb(III) in sea and surface water and total antimony in sediments and in soil. For soils different sample pretreatments were used: HNO3-H2SO4-HC1O4, HF-HNO3-H2SO4-HC1O4, cold aqua regia and slurry formation procedures in water and 4M HC1. In each case the recovery of total antimony and the ability to selective determine Sb(III) were studied. The detection limits obtained were 0.01 ng, 0.07 ng, 2.97 ng and 0.21 ppb for GF-AAS, FIA-HG-AAS, HG (Batch)-AAS, and HG (continuous flow)-AAS, respectively.
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    URL: http://dx.doi.org/10.1007/BF01243229
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    High dose oral methylprednisolone in patients with rheumatoid arthritis: pharmacokinetics and clinical response (1992)
    Springer
    European journal of clinical pharmacology 42 (1992), S. 85-88 
    Details
    ISSN: 1432-1041
    Keywords: Methylprednisolone ; Rheumatoid arthritis ; bioavailability ; pharmacokinetics ; clinical response ; pulse steroid therapy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary A commercially available 1.0 g intravenous (i.v.) dosage formulation of methylprednisolone, as the sodium hemisuccinate salt (Solu MedrolR, Upjohn) was administered both parenterally and orally (pulse steroid therapy) on separate occasions, to eight elderly (mean 65 y) patients with active rheumatoid arthritis. The relative oral bioavailability of the sterol was 69.2%. Elimination of methylprednisolone was prolonged when given orally; the mean residence times were 7.23 h and 3.94 h for oral and i.v. administrations, respectively. Clinical response to pulse steroid therapy was no different with respect to route of administration. There were no significant differences in standard clinical and laboratory assessments of disease activity when the two therapies were compared. Oral administration of methylprednisolone in patients requiring high-dose pulse steroid therapy is convenient and avoids the discomfort and inconvenience associated with i.v. administration.
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    URL: http://dx.doi.org/10.1007/BF00314925
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    Rectal bioavailability of 6-mercaptopurine in children with acute lymphoblastic leukaemia: partial avoidance of “first-pass” metabolism (1992)
    Springer
    European journal of clinical pharmacology 42 (1992), S. 619-622 
    Details
    ISSN: 1432-1041
    Keywords: 6-Mercaptopurine ; suppository ; bioavailability ; acute lymphoblastic leukaemia ; children ; interindividual variability ; pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Plasma levels and the area under the plasma concentration-time curve (AUC) values of 6-mercaptopurine (6-MP) were determined in a balanced crossover study of oral (powder) and rectal (macrogol suppository) administration to 5 children with acute lymphoblastic leukaemia (ALL). The AUC (538.6 ng · h · ml−1) after the rectal dose of 30 mg/m2 was approximately 1.5-times of that (365.5 ng · h · ml−1) after the oral dose of 87.5 mg/m2. The coefficients of variation of interindividual variability of the AUCs were 21.5% and 32.3%, respectively. The relative bioavailability of the macrogol suppository compared to the powder was approximately 4.39. These findings indicate that rectal administration of 6-MP could avoid the first-pass effect of this drug in the alimentary canal and/or liver, resulting in a large AUC of 6-MP, and so could reduce interindividual variability in plasma 6-MP concentrations. Rectal administration of 6-MP may be more effective than empirical oral dosing for the treatment of children with ALL, especially for patients with nausea and/or vomiting.
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    URL: http://dx.doi.org/10.1007/BF00265925
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    Models for describing absorption rate and estimating extent of bioavailability: Application to cefetamet pivoxil (1992)
    Springer
    Journal of pharmacokinetics and pharmacodynamics 20 (1992), S. 421-442 
    Details
    ISSN: 1573-8744
    Keywords: absorption models ; bioavailability ; cefetamet ; NONMEM ; MKMODEL ; population pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Five absorption rate models have been compared for describing cefetamet data in 34 adults after oral administration of cefetamet pivoxil with food alone or in combination with either an antacid or an H2 antagonist. A sequential zero- then first-order input process provided the most flexible description of the absorption rate of cefetamet. If the first-order rate constant is linked to the zero- order input parameters the model can be interpreted as the consequence of solubility-limited absorption. While a sequential input is theoretically reasonable to assume, the first-order process appeared to be independent of the zero-order input. A population-based approach was applied to estimate the effect of dose and gastric pH increase on absorption and disposition. There appeared to be a dose-associated change in several parameters. The most marked change was an increase in volume of distribution of cefetamet. Treatments expected to increase gastric pH slowed the first-order component of the absorption process. Three models for estimating the extent of bioavailability have been compared using observations from 18 adults and 13 children receiving iv cefetamet and oral cefetamet pivoxil on two separate occasions. The most consistent estimates of the disposition parameters and the extent of bioavailability were achieved with the sequential zero- and first- order model under the assumption that steady slate volume of distribution and nonrenal clearance were the same after iv and oral treatment.
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    URL: http://dx.doi.org/10.1007/BF01061464
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    Bioavailability of heavy metals in sediments of two coastal lagoons in Rio de Janeiro, Brazil (1992)
    Springer
    Hydrobiologia 228 (1992), S. 65-70 
    Details
    ISSN: 1573-5117
    Keywords: heavy metals ; bioavailability ; coastal lagoons ; sediments ; macrophytes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The distribution and bioavailability of trace metals in two contrasting tropical coastal lagoons were studied. The concentration of trace metals in aquatic macrophytes was compared with those found in sediments under weakly and strongly bound forms. The results showed that total metal concentrations in sediments did not explain the concentration found in plants. The highest concentrations in macrophytes were observed in the lagoon which had a higher fraction of metals weakly bound to sediments, but presented the lower total metal content. Low redox potential was the major variable keeping metals in non-bioavailable forms, possibly as refractory sulfides and metal-organic complexes. Among the macrophytes, rooted species showed lower concentrations of metals as compared to algae.
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    URL: http://dx.doi.org/10.1007/BF00006477
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    Chemical mobility and bioavailabity of sediment-bound heavy metals influenced by salinity (1992)
    Springer
    Hydrobiologia 235-236 (1992), S. 605-610 
    Details
    ISSN: 1573-5117
    Keywords: heavy metals ; sediments ; bioavailability ; transfer processes ; mobilization ; salinity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The transfer of metals from contaminated sediments to algal cell walls (Scenedesmus quadricauda) and organisms from various trophic levels (euryhaline osmoconform hydroid Cordylophora caspia and algae Brachiomonas submarina) was studied with a multichamber device. The system consists of a central chamber which contained the mud suspension and six external chambers containing the different biological indicators. The solids in the central and external chambers are separated by 0.45 μm-diameter membranes which allow diffusion of the mobilized, dissolved metal compounds. Experiments were performed with dredged sediments at various salinities (0.5, 1.0, 1.5, and 2.0 percent, respectively) and the kinetic of re-adsorption was obtained by taking samples after different time intervals. High enrichment of Cd was found in the living alga Brachiomonas submarina, but on the other side only a weak influence of salinity on re-adsorption could be observed. Model experiments with ionic Cd showed a clear dependency on Cd-sorption on the algae, Cd-concentration in solution, and salinity. These results indicate that the transfer of metals mainly depends on the specific surface properties of the substrates and on the specific chemical form of the dissolved mobilized metal.
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    URL: http://dx.doi.org/10.1007/BF00026248
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    Aspects of the chemical structure of soil organic materials as revealed by solid-state13C NMR spectroscopy (1992)
    Springer
    Biogeochemistry 16 (1992), S. 1-42 
    Details
    ISSN: 1573-515X
    Keywords: soil organic matter ; CP/MAS13C NMR ; decomposition ; bioavailability ; particle size and density fractionation ; mollisol ; oxisol ; andosol
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Solid-state cross-polarisation/magic-angle-spinning3C nuclear magnetic resonance (CP/MAS13C NMR) spectroscopy was used to characterise semi-quantitatively the organic materials contained in particle size and density fractions isolated from five different mineral soils: two Mollisols, two Oxisols and an Andosol. The acquired spectra were analysed to determine the relative proportion of carboxyl, aromatic, O-alkyl and alkyl carbon contained in each fraction. Although similar types of carbon were present in all of the fractions analysed, an influence of both soil type and particle size was evident. The chemical structure of the organic materials contained in the particle size fractions isolated from the Andosol was similar; however, for the Mollisols and Oxisols, the content of O-alkyl, aromatic and alkyl carbon was greatest in the coarse, intermediate and fine fractions, respectively. The compositional differences noted in progressing from the coarser to finer particle size fractions in the Mollisols and Oxisols were consistent with the changes noted in other studies where CP/MAS13C NMR was used to monitor the decomposition of natural organic materials. Changes in the C:N ratio of the particle size fractions supported the proposal that the extent of decomposition of the organic materials contained in the fine fractions was greater than that contained in the coarse fractions. The increased content of aromatic and alkyl carbon in the intermediate size fractions could be explained completely by a selective preservation mechanism; however, the further accumulation of alkyl carbon in the clay fractions appeared to result from both a selective preservation and anin situ synthesis. The largest compositional differences noted for the entire organic fraction of the five soils were observed between soil orders. The differences within orders were smaller. The Mollisols and the Andosol were both dominated by O-alkyl carbon but the Andosol had a lower alkyl carbon content. The Oxisols were dominated by both O-alkyl and alkyl carbon. A model describing the oxidative decomposition of plant materials in mineral soils is proposed and used to explain the influence of soil order and particle size on the chemical composition of soil organic matter in terms of its extent of decomposition and bioavailability.
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    URL: http://dx.doi.org/10.1007/BF00024251
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    Aspects of the chemical structure of soil organic materials as revealed by solid-state13C NMR spectroscopy (1992)
    Springer
    Biogeochemistry 16 (1992), S. 1-42 
    Details
    ISSN: 1573-515X
    Keywords: soil organic matter ; CP/MAS13C NMR ; decomposition ; bioavailability ; particle size and density fractionation ; mollisol ; oxisol ; andosol
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Solid-state cross-polarisation/magic-angle-spinning3C nuclear magnetic resonance (CP/MAS13C NMR) spectroscopy was used to characterise semi-quantitatively the organic materials contained in particle size and density fractions isolated from five different mineral soils: two Mollisols, two Oxisols and an Andosol. The acquired spectra were analysed to determine the relative proportion of carboxyl, aromatic, O-alkyl and alkyl carbon contained in each fraction. Although similar types of carbon were present in all of the fractions analysed, an influence of both soil type and particle size was evident. The chemical structure of the organic materials contained in the particle size fractions isolated from the Andosol was similar; however, for the Mollisols and Oxisols, the content of O-alkyl, aromatic and alkyl carbon was greatest in the coarse, intermediate and fine fractions, respectively. The compositional differences noted in progressing from the coarser to finer particle size fractions in the Mollisols and Oxisols were consistent with the changes noted in other studies where CP/MAS13C NMR was used to monitor the decomposition of natural organic materials. Changes in the C:N ratio of the particle size fractions supported the proposal that the extent of decomposition of the organic materials contained in the fine fractions was greater than that contained in the coarse fractions. The increased content of aromatic and alkyl carbon in the intermediate size fractions could be explained completely by a selective preservation mechanism; however, the further accumulation of alkyl carbon in the clay fractions appeared to result from both a selective preservation and anin situ synthesis. The largest compositional differences noted for the entire organic fraction of the five soils were observed between soil orders. The differences within orders were smaller. The Mollisols and the Andosol were both dominated by O-alkyl carbon but the Andosol had a lower alkyl carbon content. The Oxisols were dominated by both O-alkyl and alkyl carbon. A model describing the oxidative decomposition of plant materials in mineral soils is proposed and used to explain the influence of soil order and particle size on the chemical composition of soil organic matter in terms of its extent of decomposition and bioavailability.
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    URL: http://dx.doi.org/10.1007/BF02402261
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    General Treatment of the Enterohepatic Recirculation of Drugs and Its Influence on the Area Under the Plasma Level Curves, Bioavailability, and Clearance (1992)
    Springer
    Pharmaceutical research 9 (1992), S. 1306-1313 
    Details
    ISSN: 1573-904X
    Keywords: enterohepatic recirculation ; pharmacokinetics ; bioavailability ; clearance ; biliary excretion ; first-pass effect
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A general treatment of enterohepatic recirculation of drugs has been developed based on the fraction of drug in systemic circulation that is excreted in the bile and the fraction of drug reabsorbed from the gut that reaches systemic circulation in each enterohepatic cycle. The deduced equations make it possible to establish mathematical relationships between the areas under the blood level curves (AUC) of a drug when administered to normal and bile duct-cannulated animals and to predict the effect of enterohepatic recycling on bio-availability and clearance. The results were compared with those obtained by other authors using different approaches to enterohepatic recirculation, and some discrepancies were found in the equations describing the effect of enterohepatic recycling on AUC and bioavailability of drugs. The cause of such discrepancies and the problems associated with the prediction of hepatic extraction ratio from in vitro studies are discussed.
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    URL: http://dx.doi.org/10.1023/A:1015861502354
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    Sustained Propranolol Delivery and Increased Oral Bioavailability in Dogs Given a Propranolol Laurate Salt (1992)
    Springer
    Pharmaceutical research 9 (1992), S. 1507-1509 
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    ISSN: 1573-904X
    Keywords: propranolol ; bioavailability ; first-pass metabolism ; sustained-release ; absorption
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
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    URL: http://dx.doi.org/10.1023/A:1015831517800
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    The Bioinequivalence of Carbamazepine Tablets with a History of Clinical Failures (1992)
    Springer
    Pharmaceutical research 9 (1992), S. 1612-1616 
    Details
    ISSN: 1573-904X
    Keywords: carbamazepine ; human ; bioavailability ; pharmacokinetics ; dissolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The bioavailability of three lots of a generic 200-mg carbamazepine tablet, which had been withdrawn from the market, was compared to the bioavailability of one lot of the innovator product in 24 healthy volunteers. Fifty-three lots of the generic product had been recalled by the manufacturer because of concerns over reports of clinical failures for several of the lots. The three generic lots tested in this study exhibited a wide range of bioavailability, as well as large differences in the in vitro dissolution rates. The mean maximum carbamazepine plasma concentrations for two of the generic lots were only 61-74% that of the innovator product, while the third lot was 142% of the innovator. The mean areas under the plasma concentration-time curve for the three generic lots ranged from 60 to 113% that of the innovator product. The results clearly indicate a significant difference in the rate and extent of absorption of the generic products compared to the innovator, as well as among the generic lots. A good relationship was found between the in vivo parameters and the in vitro dissolution results for the four dosage forms.
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    URL: http://dx.doi.org/10.1023/A:1015872626887
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    Factors Affecting the Release Rate of Terbutaline from Liposome Formulations After Intratracheal Instillation in the Guinea Pig (1992)
    Springer
    Pharmaceutical research 9 (1992), S. 220-223 
    Details
    ISSN: 1573-904X
    Keywords: liposomes ; bronchodilators ; bioavailability ; intratracheal instillation ; pulmonary absorption ; terbutaline
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Maximum duration of bronchodilator efficacy in inhaled liposome-based formulations depends on optimizing the in vivo release rate of the encapsulated bronchodilator. We investigated the effect of several formulation variables on the pulmonary residence time of 3H-terbutaline sulfate liposomes administered intratracheally in guinea pigs, using an improved method enabling the measurement of pulmonary drug absorption for extended periods of time in conscious animals. Half-lives of liposome-encapsulated 3H-terbutaline disappearance from the lungs and airways after instillation ranged from 1.4 to 18 hr and were markedly affected by liposome size, cholesterol content, and phospholipid composition. This study demonstrates that liposomes can significantly prolong the residence time of bronchodilators in the lungs and that precise control over the pulmonary residence time of encapsulated bronchodilators can be achieved by controlling formulation variables.
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    URL: http://dx.doi.org/10.1023/A:1018989423909
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    In Vivo Percutaneous Absorption of Hydrocortisone: Multiple-Application Dosing in Man (1992)
    Springer
    Pharmaceutical research 9 (1992), S. 1164-1167 
    Details
    ISSN: 1573-904X
    Keywords: hydrocortisone ; multiple dose ; bioavailability ; absorption ; acetone ; human in vivo
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Percutaneous absorption of hydrocortisone was measured in six healthy adult men from whom informed consent had been obtained. The study compared a single topical dose to multiple-topical dose treatments (one vs three applications) on the same day. 14C-Labeled hydrocortisone in acetone was applied to 2.5 cm2 of ventral forearm skin and protected with a nonocclusive polypropylene chamber. The amount of 14C measured in urine collected over 7 days was used to determine hydrocortisone absorption. The treatments, performed 2 to 3 weeks apart, each utilized adjacent sites on the same individuals. A single dose of 13.33 µg/cm2 delivered 0.056 µg/cm2 of hydro-cortisone through the skin. When the single dose was tripled to 40 µg/cm2, the amount delivered through the skin increased by nearly three times, from 0.056 to 0.140 µg/cm2; the expected delivery was 3 x 0.056 µg/cm2 = 0.168 µg/cm2. Three serial doses of 13.33 µg/ cm2 (total, 40 µg/cm2) were also expected to deliver 0.168 µg/cm2 with or without soap and water washing between doses, but the observed amount of hydrocortisone delivered through the skin significantly exceeded our expectations. This indicates that multiple-dosing treatments resulted in a significant increase in bioavailability. It is postulated that increased vehicle application and washing dissolved and mobilized previously dosed hydrocortisone and increased bioavailability.
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    Feasibility of Measuring the Bioavailability of Topical Betamethasone Dipropionate in Commercial Formulations Using Drug Content in Skin and a Skin Blanching Bioassay (1992)
    Springer
    Pharmaceutical research 9 (1992), S. 45-51 
    Details
    ISSN: 1573-904X
    Keywords: bioavailability ; skin blanching ; vasoconstriction ; topical corticosteroids ; betamethasone dipropionate ; tape-stripping
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract An in vivo technique has been developed which simultaneously compares a skin blanching bioassay with drug content in human stratum corneum following topical application of four 0.05% beta-methasone dipropionate formulations. Bioavailability of drug from commercial cream and ointment formulations was assessed by quantification of drug content in tape-stripped stratum corneum and skin blanching in the treated skin site under occluded conditions. Tape-stripping removed stratum corneum to a varying degree between individuals but was consistent (35%) within an individual with all formulations, day to day. A correlation (r = 0.9935) between the amount of drug in the treated stratum corneum normalized for surface area and the corresponding skin blanching score was observed with four 0.05% betamethasone dipropionate formulations. Increasing the amount of drug in the tape-stripped stratum corneum correlated with an increased skin blanching score. Ointment formulations delivered more drug to the skin and produced greater blanching scores than the cream formulations. Topical corticosteroid content in the treated skin site can therefore be quantified and correlates well with the resulting pharmacodynamic activity.
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    Bioequivalence (1992)
    Springer
    Pharmaceutical research 9 (1992), S. 925-928 
    Details
    ISSN: 1573-904X
    Keywords: bioequivalence ; bioavailability ; plasma concentration function ; AUG
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The bioequivalence of two formulations of the same drug may be determined by evaluating the similarity of their respective plasma concentration curves. The similarity of two plasma concentration functions can be measured by an index called the bioequivalence index. This paper shows how such an index may be defined and calculated.
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    Enhanced Bioavailability of 6-Mercaptopurine After Rectal Administration in Rats (1992)
    Springer
    Pharmaceutical research 9 (1992), S. 697-699 
    Details
    ISSN: 1573-904X
    Keywords: 6-mercaptopurine ; bioavailability ; macrogol ; Witepsol ; rectal administration ; first-pass effect
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
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    URL: http://dx.doi.org/10.1023/A:1015874732029
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    Wirkung von Maillard-Produkten und Lysinoalanin auf die Bioverfügbarkeit von Eisen, Kupfer und Zink (1991)
    Springer
    European journal of nutrition 30 (1991), S. 50-55 
    Details
    ISSN: 1436-6215
    Keywords: Maillard-Produkte ; LAL ; Bioverfügbarkeit ; Eisen ; Kupfer ; Zink ; Maillard products ; LAL ; bioavailability ; iron ; copper ; zinc
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Medicine
    Description / Table of Contents: Summary Bioavailability of iron, copper, and zinc was investigated in suckling rats. The essential trace elements were given once either with several isolated Maillard products and with LAL, respectively, or with differently heat-treated formula diets. The isolated substances revealed effects on bioavailability of all the elements tested, either on the preresorptive or on the postresorptive level. The formula diets affected only the bioavailability of copper — even when fed for several weeks.
    Notes: Zusammenfassung Es wurde die Bioverfügbarkeit von Eisen, Kupfer und Zink untersucht, wenn diese essentiellen Spurenelemente 1. mit einigen isolierten Maillard-Produkten bzw. LAL, oder 2. mit thermisch unterschiedlich belasteten Testnahrungen einmalig an Säuglingsratten verabreicht wurden. Durch die isolierten Testsubstanzen ließen sich bei allen drei Elementen Effekte auf der präresorptiven und/oder postresorptiven Ebene erzielen. Die Testnahrungen beeinflußten — auch wenn sie fünf Wochen lang verfüttert wurden — nur die Bioverfügbarkeit des Kupfers.
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    Absolute bioavailability of nicotine applied to different nasal regions (1991)
    Springer
    European journal of clinical pharmacology 41 (1991), S. 585-588 
    Details
    ISSN: 1432-1041
    Keywords: Nicotine ; bioavailability ; nasal spray
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The absolute bioavailability of nicotine administered nasally, as drops to the nasal conchae and nasal septum, and as a nasal spray, has been studied in eight healthy volunteers. Single nasal doses of 1 mg nicotine were given and plasma concentrations of nicotine were followed for 6 h. Compared to an intravenous infusion of nicotine, the bioavailability of the nasal administrations was 60 to 75%. The rate of absorption was fast, the maximum concentration being reached after about 10 min. In the present study, there was no significant difference in the rate or extent of absorption between the different nasal treatments.
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    URL: http://dx.doi.org/10.1007/BF00314989
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    Pharmacokinetics of midazolam in children: comparative study of intranasal and intravenous administration (1991)
    Springer
    European journal of clinical pharmacology 41 (1991), S. 355-357 
    Details
    ISSN: 1432-1041
    Keywords: Midazolam ; pharmacokinetics ; intranasal ; intravenous ; children ; bioavailability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Twelve children 1–5 y old were randomly assigned to receive midazolam 0.2 mg·kg−1 either by the intravenous (IV) or intranasal (IN) routes. After IN administration the rapid onset of absorption was observed (tmax 12 min). After both routes of administration the half-life was similar (2.2 h IN and 2.4 h IV). After IN administration the apparent plasma clearance and volume of distribution were about twice as high as after IV administration. The results are consistent with an estimated mean bioavailability of 55%.
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    Decreased and variable systemic availability of zidovudine in patients with AIDS if administered with a meal (1991)
    Springer
    European journal of clinical pharmacology 40 (1991), S. 305-308 
    Details
    ISSN: 1432-1041
    Keywords: Zidovudine ; acquired immunodeficiency syndrome (AIDS) ; pharmacokinetics ; bioavailability ; food intake
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The systemic availability of oral zidovudine has been studied in 13 patients with the acquired immunodeficiency syndrome (AIDS) dosed either fasting or with breakfast. The mean peak plasma concentration and AUC of zidovudine were significantly 2.8- and 1.4-times higher in fasting patients than in those treated during meal. In both conditions the mean half-life was about 1.5 h and the period of plasma zidovudine concentrations 〉1 μmol · l−1 was 2 h (NS). It is concluded that if zidovudine is taken on an empty stomach, high peak plasma concentrations and decreased variation in pharmacological parameters may be expected. Whether or not this will influence toxicity and efficacy remains to be shown.
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    URL: http://dx.doi.org/10.1007/BF00315215
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    Enhancement of propoxyphene bioavailability by ethanol (1991)
    Springer
    European journal of clinical pharmacology 41 (1991), S. 147-152 
    Details
    ISSN: 1432-1041
    Keywords: Propoxyphene-Ethanol Interaction ; bioavailability ; healthy volunteers ; psychomotor performance drug interaction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The interaction between a single oral dose of 130 mg propoxyphene and 0.5 g/kg body weight ethanol was investigated in 12 healthy male volunteers by 9 objective performance tests, 8 visual analogue self-rating scales and the measurement of plasma propoxyphene, norpropoxyphene and ethanol concentrations, using a double-blind threeway crossover design. Volunteers were each given one of three treatments, propoxyphene + ethanol, placebo + ethanol and propoxyphene alone, separated by a two week interval. The performance tests were completed before and 1.25 and 4 h after drug intake, and the self-rating scales before and 1.25, 4 and 10 h after it. Ethanol was shown to enhance the bioavailability of propoxyphene by 25% probably by reducing its first-pass metabolism. However, despite this pharmacokinetic effect no pharmacodynamic interaction was found. Subjective ratings disclosed that the effect of ethanol on physical and mental sedation predominated over the effects of propoxyphene.
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    Comparison of the bioavailability of two slow release preparations of disopyramide (1991)
    Springer
    European journal of clinical pharmacology 40 (1991), S. 629-630 
    Details
    ISSN: 1432-1041
    Keywords: Disopyramide ; slow release ; plasma concentrations ; bioavailability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The bioavailability of two slow release preparations of disopyramide has been compared in a randomized cross-over trial of Rythmodan L. A. 250 mg b. d. and Dirytmin Durettes 300 mg b. d., given to 10 healthy volunteers. The plasma concentrations of disopyramide were measured on the 5th day of each treatment period. With both preparations, plasma concentrations were well sustained. The amount absorbed was slightly lower after Rythmodan L. A. than after Dirytmin Durettes, but the fluctuations over a dosing interval were significantly more pronounced for Dirytmin Durettes than for Rythmodan L. A.
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    Magnesium-L-aspartate-HCl and magnesium-oxide: bioavailability in healthy volunteers (1991)
    Springer
    European journal of clinical pharmacology 40 (1991), S. 437-438 
    Details
    ISSN: 1432-1041
    Keywords: Magnesium deficiency ; oral replacement therapy ; bioavailability ; adverse effects
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
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    URL: http://dx.doi.org/10.1007/BF00265863
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    Cyclosporine pharmacokinetics in liver transplant recipients: evaluation of results using both polyclonal radioimmunoassay and liquid chromatographic analysis (1991)
    Springer
    European journal of clinical pharmacology 40 (1991), S. 513-519 
    Details
    ISSN: 1432-1041
    Keywords: Cyclosporine ; liver transplant recipients ; radioimmunoassay ; pharmacokinetics ; bioavailability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Pharmacokinetic variables were derived from cyclosporine measurements using liquid chromatography (HPLC) and radioimmunoassay with a non-selective polyclonal antibody (PARIA) in 11 orthotopic liver transplant recipients studied in paired oral and intravenous studies both before and after permanent clamping of the biliary T-tube. After oral drug administration, mean areas under blood cyclosporine concentration versus time curves before clamping were around 5.2-fold greater by PARIA than HPLC but 2.9-fold greater after clamping and closer to comparable values after intravenous cyclosporine (2.5 and 2.3-fold, respectively). Cyclosporine clearance was smaller by PARIA than HPLC (mean 7.3 versus 3.3 ml · min−1 · kg−1, respectively, before clamping). Both values decreased by 25% after clamping (to 5.5 and 2.4 ml · min−1 · kg−1, respectively), although there was no significant change in distribution or elimination half-lives (around 0.5 and 8 h, respectively). The mean bioavailability of oral cyclosporine increased significantly after clamping in 9 patients (from 10.6% to 28.1% by HPLC and from 14.8 to 35.1% by PARIA) but in two patients who developed the vanishing bile duct syndrome values fell to 〈 10% and the proportional overestimation of cyclosporine concentrations by PARIA increased. Clamping had no significant effect on the mean apparent volumes of distribution but values of Vz were approximately twice those of Vss (around 2.6 and 1.3 l · kg−1 by PARIA and HPLC respectively). Mean half lives after clamping were shorter following oral than intravenous cyclosporine (t1/2λ2 around 15 h enterally versus 8 h parenterally). These data suggest delays in cyclosporine absorption and significant first pass metabolism which may contribute to higher PARIA:HPLC ratios after oral dosing and to reduced bioavailability before clamping.
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    Trace metals in the benthic habitat of the Maarsseveen Lakes system, The Netherlands (1991)
    Springer
    Aquatic ecology 24 (1991), S. 153-164 
    Details
    ISSN: 1573-5125
    Keywords: trace metals ; benthos ; invertebrates ; sediment ; bioavailability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The cadmium, zinc, lead and copper concentrations in benthic invertebrates and sediment were determined during two consecutive winters in the Maarsseveen Lakes system. A sequential extraction procedure was applied to estimate the bioavailability of the trace metals in the sediment. Based on the trace metal analyses of organisms and sediment, it is concluded that the Maarsseveen Lakes system has background levels of cadmium, zinc, lead and copper. As the majority of metals was present in geochemically more stable sediment phases, the sequential extractions provided limited additional information on trace metal bioavailability.
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    Pharmacokinetics and bioavailability of diclofenac in the rat (1991)
    Springer
    Journal of pharmacokinetics and pharmacodynamics 19 (1991), S. 647-665 
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    ISSN: 1573-8744
    Keywords: diclofenac sodium ; biliary excretion ; pharmacokinetics ; bioavailability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Diclofenac sodium is a widely used drug with interesting absorption and disposition features when administered to laboratory animals. The present study was undertaken to assess the pharmacokinetics of the drug after iv and gastrointestinal dosing to rats. Renal excretion of unchanged drug was negligible, but biliary excretion of the drug (unchanged and conjugated) was detected in bile duct-cannulated rats; it accounted for 27.2 and 31.2% of the total dose following iv and intraduodenal administration, respectively. Most of the drug excreted in the bile was conjugated diclofenac; unchanged drug accounted for only 4.7 and 5.4% of total diclofenac excreted in the bile after iv and intraduodenal dosing, respectively. In normal animals, intestinal absorption of the drug excreted in the bile resulted in higher drug concentrations in plasma than those obtained in bile duct-cannulated rats, but only after 60 min of dosing. When administered directly into the duodenum, diclofenac absorption was extremely fast and the maximum plasma diclofenac concentration was reached within 2 min. After oral dosing, an early peak was also observed, but it was lower than that obtained after intraduodenal dosing: 71% diclofenac hioavailability was found in bile duct-cannulated rats intraduodenally dosed, whereas in normal animals dosed by mouth a bioavailability of 79% was obtained. In normal animals intraduodenally dosed, an apparent bioavailability of 106% was observed. All of these features, particularly the influence of enterohepatic circulation on drug bioavailability, are discussed.
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    Maximum entropy and drug absorption (1991)
    Springer
    Journal of pharmacokinetics and pharmacodynamics 19 (1991), S. 497-520 
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    ISSN: 1573-8744
    Keywords: Bayes' theorem ; maximum entropy ; deconvolution ; absorption rate ; input rate ; bioavailability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The application of maximum entropy to the calculation of drug absorption rates was introduced in an earlier paper. Here it is developed further, and the whole procedure is presented as a problem in scientific inference to be solved using Bayes' theorem. Blood samples do not need to be taken at equally spaced intervals, and no smoothing, interpolation, extrapolation, or other preprocessing of the data is necessary. The resulting input rate estimates are smooth and physiologically realistic, even with noisy data, and their accuracy is quantified. Derived quantities such as the proportion of the dose absorbed, and the mean and median absorption times, are also obtained, together with their error estimates. There are no arbitrarily valued parameters in the analysis, and no specific functional form, such as an exponential or polynomial, is assumed for the input rate functions.
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    The bioavailability of cadmium to lettuce and cabbage in soils previously treated with sewage sludges (1991)
    Springer
    Plant and soil 132 (1991), S. 179-186 
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    ISSN: 1573-5036
    Keywords: bioavailability ; cabbage ; cadmium ; lettuce ; sewage sludge treated soils
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The application of sewage sludges to soils may lead to increased soil-Cd levels. The bioavailability of Cd is determined by the interaction of a number of soil physico-chemical and plant variables, of which pH is the most important. Duplicate samples of sludge-treated soils were transferred to tubs in the field, one of each pair being limed to pH 7±0.5. Lettuce and cabbage were grown to maturity and analysed for Cd. Liming always reduced Cd uptake by the plants. Three soil extractants, 1 M NH4NO3, 0.05 M EDTA-(Na)2 and 0.05 M CaCl2 were used as indices of Cd bioavailability. CaCl2 proved to be the most effective for both lettuce and cabbage. Multiple linear regression equations were derived to describe the uptake and accumulation of Cd by both crops. The relative influence of soil variables differed between the two species. Unlike those of a number of pot experiments conducted in glasshouses, the data from this experiment are comparable with those of crop samples taken from the field.
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    Bioavailability of Erythromycin Acistrate from Hard Gelatin Capsules Containing Sodium Bicarbonate (1991)
    Springer
    Pharmaceutical research 8 (1991), S. 1056-1058 
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    ISSN: 1573-904X
    Keywords: erythromycin acistrate ; erythromycin ; bioavailability ; sodium bicarbonate ; high-performance liquid chromatography (HPLC)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Erythromycin acistrate is a new prodrug of erythromycin. Its bioavailability from hard gelatin capsules containing the drug with or without sodium bicarbonate was studied in healthy volunteers. The plasma levels of erythromycin, anhydroerythromycin, and acetylerythromycin were measured using an HPLC method. Addition of sodium bicarbonate to the capsule markedly enhanced the plasma level of the microbiologically active substance, erythromycin, doubling the C max and AUC values (P 〈 0.05). At the same time, the lag time in the absorption curve was shortened to one-third. No changes in the plasma levels of the inactive metabolite anhydroerythromycin were noted. It is concluded that adding sodium bicarbonate to an erythromycin acistrate formulation enhances its bioavailability.
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    Formulation, Bioavailability, and Pharmacokinetics of Sustained-Release Potassium Chloride Tablets (1991)
    Springer
    Pharmaceutical research 8 (1991), S. 1313-1317 
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    ISSN: 1573-904X
    Keywords: potassium chloride ; sustained-release tablets ; formulation ; in vitro evaluation ; bioavailability ; pharmacokinetics ; in vitro–in vivo evaluation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The release of potassium chloride incorporated into hydrogenated vegetable oil and hydroxypropyl methylcellulose matrix tablets was studied in vitro. The formulations containing 20% hydrogenated vegetable oil and hydroxypropyl methylcellulose showed a sustained-release profile comparable to that of a standard commercially available sustained-release preparation, containing 8 mEq potassium chloride embedded in a wax material. The formulated and standard sustained-release potassium chloride tablets were compared to a conventional enteric-coated potassium chloride tablet in 10 healthy subjects. Mean recoveries in 24-hr urine potassium levels from four dosage forms (after subtracting normal urine potassium excretion levels) were 76 ± 32% from hydroxypropyl methylcellulose, 95 ± 22% from hydrogenated vegetable oil-incorporated matrix tablets, 91 ± 29% from commercially available sustained-release tablets, and 97 ± 13% from enteric-coated tablets. There was no significant difference (P 〉 0.05) in the time to reach maximum excretion rates among the three sustained-release tablets. No significant adverse effect was experienced with any of the preparations.
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    Extent and Variability of the First-Pass Elimination of Adinazolam Mesylate in Healthy Male Volunteers (1991)
    Springer
    Pharmaceutical research 8 (1991), S. 162-167 
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    ISSN: 1573-904X
    Keywords: adinazolam ; N-desmethyladinazolam ; unbound fraction ; hepatic extraction ratio ; bioavailability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The pharmacokinetics of adinazolam and N-desmethyladinazolam (NDMAD) were studied in 14 healthy male volunteers who received 15 mg adinazolam mesylate orally as a solution and 5 mg adinazolam mesylate intravenously in a crossover design. Two weeks prior to the crossover study, each subject received 5 mg/kg indocyanine green (ICG) as an intravenous bolus injection to estimate liver blood flow. The absolute bioavailability (F), calculated as the dose-corrected ratio of oral to iv adinazolam area under the curve (AUC) values, was found to be 39%. NDMAD AUC values were similar following oral and iv administration, and adinazolam mean absorption time was approximately 0.77 hr. Thus, adinazolam is completely and rapidly absorbed after oral administration in man; the incomplete bioavailability is due to first-pass metabolism. Mean liver blood flow, adinazolam systemic clearance, blood/plasma ratio, and extraction ratio were 1189 ml/min, 498 ml/min, 0.70, and 0.57, respectively. The extraction ratio agrees with that calculated as 1-F (0.62), suggesting that the liver is primarily responsible for first-pass metabolism of adinazolam. The unbound fraction of adinazolam in plasma was 0.31 (range, 0.25–0.36); adinazolam free intrinsic clearance (a reflection of metabolic capacity) was 4285 ml/min (range, 2168–6312 ml/min). These results suggest that the majority of the variability in adinazolam plasma concentrations following oral administration is due to the variability in the metabolic capacity of the liver for adinazolam, rather than variability in plasma protein binding.
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    Pharmacokinetic Study of an Iridoid Glucoside: Aucubin (1991)
    Springer
    Pharmaceutical research 8 (1991), S. 1059-1063 
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    ISSN: 1573-904X
    Keywords: aucubin ; preformulation study ; pharmacokinetics ; bioavailability ; pH-stability ; partition coefficient ; iridoid glucoside
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Aucubin, a promising hepatoprotecting iridoid glucoside, was given intravenously (iv), orally (po), intraperitoneally (ip), and hepatoportally (pv) to rats. A linear pharmacokinetic behavior was obtained after iv administration of 40–400 mg/kg of aucubin. The half-life of aucubin in the postdistributive phase (t 1/2,β), total-body plasma clearance (CL t), and volume of distribution (Vd ss) were 42.5 min, 7.2 ml/min/kg, and 346.9 ml/kg, respectively, for a 40 mg/kg dose. There was no significant difference in the parameters as a result of increasing dose. The partition coefficients of aucubin between n-octanol and buffers of pH 3.0–10.0 were low, while 18.5 ± 1.3% of aucubin in whole blood partitioned into the blood cells. Plasma protein binding of aucubin was only 9%. The bioavailabilities of aucubin after administration at a dose of 100 mg/kg through pv, ip, and po routes were 83.5, 76.8, and 19.3%, respectively. The pH-stability profile indicated rapid degradation of aucubin at pH 1.2, 1.6, and 2.0, with degradation half-lives of 5.1, 5.8, and 14.8 hr, respectively, at 37°C. Therefore, the low oral bioavailability of aucubin may be attributed to pH-instability in the gastric fluid, poor GI absorption due to low lipophilicity, and the possible metabolism in the GI mucosa and liver (so called first-pass effect).
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    Enhanced Bioavailability of Subcutaneously Injected Insulin by Pretreatment with Ointment Containing Protease Inhibitors (1991)
    Springer
    Pharmaceutical research 8 (1991), S. 60-64 
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    ISSN: 1573-904X
    Keywords: insulin ; subcutaneous administration ; protease inhibitor ; gabexate ; nafamostat ; ointment ; bioavailability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The present study was undertaken to develop an ointment preparation containing a protease inhibitor for stabilizing subcutaneously injected insulin. The ointment containing the protease inhibitor, gabexate mesilate or nafamostat mesilate, was applied to the skin around the insulin injection site. Three results were obtained. First, gabexate and nafamostat inhibited insulin degradation in subcutaneous tissue homogenates in vitro. Second, after application of gabexate or nafamostat ointment, an appreciable amount of gabexate or nafamostat appeared in the subcutaneous tissue of rats or hairless mice and their concentrations were comparable to those seen in the in vitro experiment. Third, insulin degradation at the subcutaneous injection site in the rat was depressed after pretreatment with gabexate or nafamostat ointment. Pretreatment with gabexate or nafamostat ointment increased the plasma immunoreactive insulin (IRI) levels and the hypoglycemic effect of insulin in healthy volunteers. These results indicate that gabexate or nafamostat ointments stabilize subcutaneously injected insulin.
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    In Vitro and in Vivo Evaluation of Whole and Half Tablets of Sustained-Release Adinazolam Mesylate (1991)
    Springer
    Pharmaceutical research 8 (1991), S. 1482-1488 
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    ISSN: 1573-904X
    Keywords: adinazolam mesylate ; oral sustained release ; matrix sustained release ; mechanism ; in vivo/in vitro correlation ; bioavailability ; absorption
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The mechanism of release from sustained-release adinazolam mesylate tablets was assessed by the Higuchi equation and by analysis of drug release profiles through 60% released using the Peppas equation. Computed values of the diffusional exponent, n, ranged from 0.59 to 0.66. Values of n in this range are consistent with a mixed mechanism of release, with diffusion of drug through the hydrated polymer matrix and relaxation of this matrix being the principal processes controlling release. The rate of in vitro drug release was increased for half tablets relative to whole tablets and is attributed to an increase in the surface to volume ratio of half tablets of about 16%. This increase in surface-to-volume ratio of half tablets was reflected by an increase in the constant, k, from the Peppas equation of 20–23% and by an increase in the slope of Higuchi plots of 12–18% for four lots of tablets. In vivo/in vitro relationships from two bioavailability studies were thoroughly evaluated. Using either a linear or a quadratic relationship, an in vivo/in vitro correlation exists for sustained-release adinazolam mesylate tablets.
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    Suitability of Various Noninfinity Area Under the Plasma Concentration–Time Curve (AUC) Estimates for Use in Bioequivalence Determinations: Relationship to AUC from Zero to Time Infinity (AUCO–INF) (1991)
    Springer
    Pharmaceutical research 8 (1991), S. 512-517 
    Details
    ISSN: 1573-904X
    Keywords: area under the plasma concentration–time curve (AUC) ; bioavailability ; noninfinity AUC estimates ; 90% confidence intervals ; danazol ; baclofen ; oxazepam
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The influence of random error and elimination rate on estimates of the area under the curve from zero to time infinity (AUC0–INF) was determined in a simulation study using noninfinity measured AUC values (i.e., AUCTM, area to a measured common sampling time, and AUC0-LAST, area to the last measured sampling time). Further, the extent of absorption of generic danazol, baclofen, and oxazepam was determined using measured methods of estimating area under the curve in bioequivalence studies. The noninfinity AUC estimates and their 90% confidence intervals for the difference in product means were compared for each individual drug. Products chosen fulfilled one of the following three criteria: (1) a high “apparent intrasubject variability” and a half-life greater than 8 hr (danazol); (2) a low apparent intrasubject variability and a half-life less than 4 hr (baclofen); and (3) products exhibiting a low apparent intrasubject variability and a half-life greater than 8 hr (oxazepam). For the simulated data, AUCTM performed best when subjects had similar half-lives (i.e., low variability), which results in AUCTM = AUC0–LAST. On the other hand, AUC0–LAST worked best with a high fractional standard deviation (fsd) and a short elimination half-life (i.e., less than 4 hr). The noninfinity 90% confidence intervals for danazol and oxazepam were inconsistent with those observed at AUC0–INF. However, baclofen, which has a short elimination half-life, exhibited good agreement between the noninfinity and the AUC0–INF 90% confidence intervals. However, across all three drug groups, the comparison based upon the area calculated from time zero to the last quantifiable concentration, AUC0–LAST, consistently provided the best approximation of AUC0–INF.
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    The Preparation and Evaluation of a Tablet Dosage Form of Cyclosporine in Dogs (1991)
    Springer
    Pharmaceutical research 8 (1991), S. 518-522 
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    ISSN: 1573-904X
    Keywords: cyclosporine ; dosage form ; bioavailability ; pharmacokinetics ; dogs ; tracer
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Cyclosporine (CsA) is commercially available for oral administration as a solution in olive oil with alcohol and an emulsifier. To improve its variable absorption and low patient acceptability, several oral formulations were prepared and tested in vitro and in vivo in dogs. A tablet formulation prepared by direct compression was then selected for comparison with the commercial oil solution placed into soft gelatin capsules. The study involved a randomized crossover design in six dogs. In order to determine absolute bioavailability and to compensate for any time-dependent changes in clearance, an intravenous tracer dose of 3H-CsA was administered along with each oral test product on each of two occasions. Absolute bioavailability (mean ± SD) was 46.0 ± 11.1 and 45.4 ± 9.9% for the capsules and tablets, respectively. C max, t max, and mean absorption time were not significantly different between the two products. No differences were observed in the pharmacokinetics of the intravenously administered CsA in the two experiments, which were separated by 8–13 days. We conclude that the proposed tablet formulation for CsA is equivalent in dogs to the commercial dosage form placed into soft gelatin capsules.
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    Bioavailability of Flurbiprofen Following Buccal Administration (1991)
    Springer
    Pharmaceutical research 8 (1991), S. 605-607 
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    ISSN: 1573-904X
    Keywords: bioavailability ; flurbiprofen ; buccal administration ; periodontal disease
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The buccal absorption of flurbiprofen was evaluated in nine normal volunteers. Twenty milliliters of 2.5 mg/ml flurbiprofen solution (pH 8.03) was administered as a 1-min mouthwash or a 5-min mouthwash or swallowed. Serum was harvested from blood samples taken at specified times over a 12-hr period. Serum flurbiprofen concentration data indicate that the extent, but not the rate, of drug absorption was dependent upon the time of exposure of the flurbiprofen solution to the buccal membrane. Following the 1- and 5-min mouthwash treatments, 5.2 and 9.4% of the administered doses were absorbed, respectively.
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    The Bioavailability and Nonlinear Clearance of (–)-Carbovir in the Rat (1991)
    Springer
    Pharmaceutical research 8 (1991), S. 739-743 
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    ISSN: 1573-904X
    Keywords: (–)-carbovir ; bioavailability ; nonlinear clearance ; Sprague–Dawley rats
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The pharmacokinetics and bioavailability of (±)-carbovir, a carbocyclic nucleoside active against human immunodeficiency virus, have been described previously. To determine the bioavailability of (–)-carbovir, the biologically active enantiomer, four male Sprague–Dawley rats received 18 mg/kg of (–)-carbovir through the jugular vein and 54 mg/kg orally. Following the pilot studies, five rats were randomly assigned to receive (–)-carbovir in a three-way crossover design as either a single 18-mg/kg iv bolus, a single 54-mg/kg oral dose, or a single iv infusion of 18 mg/kg to achieve a target steady-state concentration (C ss) of 1 µg/ml, the peak concentration after an oral dose. Blood and urine samples were analyzed by an improved ion-paired reversed-phase HPLC method with fluorescence detection. Blood concentrations of (–)-carbovir declined in a biphasic manner after the iv bolus dose. The terminal half-life was 116 and 106 min after the iv bolus and oral dose, respectively. The blood/plasma distribution ratio was approximately 1.0 in the range of 1 to 10 µg/ml of (–)-carbovir in blood. The free fraction in serum was concentration dependent. Significant differences in the renal, nonrenal, and total-body clearances after the iv bolus and iv infusion suggested nonlinear elimination of (–)-carbovir. The oral bioavailabilities derived from blood data were significantly different when the iv bolus was used as a reference rather than the iv infusion. However, the bioavailabilities were not significantly different when the total urinary excretion of unchanged (–)-carbovir after iv bolus or infusion was used as a reference. Concomitant saturation of renal and nonrenal clearances might explain these findings. The oral bioavailability was about 20% at concentrations approximating 1 µg/ml in blood.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1015850017201
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  • 88
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    Vergleich der biologischen Aktivität und Stabilität von Menadion und Menadiol bei Hühnerküken (1990)
    Springer
    European journal of nutrition 29 (1990), S. 219-228 
    Details
    ISSN: 1436-6215
    Keywords: Vitamin K ; Menadion ; Menadiol ; Bioverfügbarkeit ; Stabilität ; Geflügel ; vitamin K ; menadione ; menadiol ; bioavailability ; stability ; poultry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Medicine
    Description / Table of Contents: Summary A bioassay of vitamin K is described, based on the prothrombin clotting time of 3-week-old, vitamin-K-depleted, and cumatetralyl-sensitized male broiler chicks, using a homologous thrombokinase preparation. With this test it could be shown that the diacetate and dibutyrate esters of menadiol are vitamin-K-active. The bioactivity of menadione from these menadiolesters amounted to about 70 % of the standard menadione from a coated menadione sodium bisulfite (Dohyfral). Menadiol seems to be temperature-resistant under such conditions, whereby two uncoated MSB preparations lost about 60 % of their activity.
    Notes: Zusammenfassung In einem biologischen Testverfahren an Cumatetralyl sensibilisierten Küken konnte in 3 Versuchen anhand des Parameters Thromboplastinzeit mit homologer Thrombokinase gezeigt werden, da\ Menadioldiacetat und Menadioldibutyrat Vitamin-K-wirksam sind. Die biologische Wirksamkeit von Menadion aus diesen Menadiolestern betrug ca. 70 % der Menadionaktivität aus gecoatetem Menadionbisulfit (Dohyfral®). Im Gegensatz zu 2 ungeschützten MSB-Präparationen, welche bei Wärmebelastung ca. 60 % ihrer ursprünglichen Wirkung verloren, waren die Menadiolester temperaturstabil.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02023079
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  • 89
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    Comparative bioavailability of diclofenac hydroxyethylpyrrolidine vs diclofenac sodium in man (1990)
    Springer
    European journal of clinical pharmacology 38 (1990), S. 207-208 
    Details
    ISSN: 1432-1041
    Keywords: diclofenac ; oral administration ; bioavailability ; healthy subjects ; diclofenac hydroxyethylpyrrolidine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary A pharmacokinetic study in man has been made of a new dosage form of diclofenac hydroxyethylpyrrolidine (DIEP); soluble salt packed in sachets was compared with diclofenac sodium as enteric coated tablets. Oral DIEP 2×50 mg showed a significant difference in absorption kinetics (ka, lag time and tmax) as compared to oral diclofenac sodium 2×50 mg. A relevant plasma concentration of diclofenac was detected just 15 min after DIEP, while diclofenac sodium produced a measurable plasma concentration only 0.5–1 h after the treatment. Cmax and t1/2 after DIEP and diclofenac sodium were comparable. Comparison of the two AUC values showed that DIEP was bioequivalent to diclofenac sodium (Q=100%).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00265987
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  • 90
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    Pharmacokinetics of isradipine in patients with chronic liver disease (1990)
    Springer
    European journal of clinical pharmacology 38 (1990), S. 599-603 
    Details
    ISSN: 1432-1041
    Keywords: Isradipine ; cirrhosis ; systemic ; calcium antagonist ; aminopyrine breath test ; serum bile acids ; galactose elimination ; pharmacokinetics ; bioavailability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The pharmacokinetics of the dihydropyridine calcium antagonist isradipine has been examined in 8 healthy volunteers, 7 patients with non-cirrhotic chronic liver disease (CLD), and 8 patients with biopsy-proven cirrhosis (CIR). Isradipine was simultaneously given orally (12C 5 mg) and i.v. (13C 1 mg). Systemic availability was significantly increased from 17% and 16% in controls and CLD, respectively, to 37% in CIR. The corresponding systemic clearances averaged 1.1, 0.9 and 0.61 · min−1, the reduction in cirrhotics being significant. Both aminopyrine demethylation capcity, a measure of hepatic microsomal function, and indocyanine green disappearance, a measure of hepatic perfusion, were correlated with the reduction in systemic clearance, and the reduction in oral clearance was correlated with the reciprocal of the serum bile acid concentration. The loss of first-pass extraction should be considered when this calcium antagonist is given perorally in patients with hepatic cirrhosis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00278589
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  • 91
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    Mechanisms and variations in the food effect on propranolol bioavailability (1990)
    Springer
    European journal of clinical pharmacology 38 (1990), S. 469-475 
    Details
    ISSN: 1432-1041
    Keywords: propranolol ; bioavailability ; presystemic metabolism ; food effect
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Mechanisms and variations in the food-induced increase in the bioavailability of propranolol were assessed by single-dose (80 mg) studies in healthy volunteers who took the drug on an empty stomach, immediately after a protein-rich breakfast, and together with a carbohydrate-rich, protein-poor breakfast. Concomitant intake of the protein-rich, but not the carbohydrate-rich, protein-poor breakfast, increased the bioavailability of propranolol in most, but not all, subjects. The food (protein) effect displayed much inter-individual variation, from a decrease to a 250% increase, which could be explained, at least in part, by a correlation between the oral clearance of propranolol and the food-induced increase in its bioavailability. The food effect was not associated with decreased total availability, but with delayed appearance, of the oxidative metabolites 4-OHP, NLA and PG. Hence the food (protein) effect does not seem to be caused by enzyme inhibition, but rather it is due to reduced hepatic extraction of propranolol, probably consequent to an increased hepatic entry rate. When taken together with the protein-rich breakfast, propranolol usually appeared in systemic blood at least as early as when taken on an empty stomach, implying that gastric absorption of propranolol may be possible in the presence of protein-rich food. Within the individual the food effect was reproducible, but its magnitude showed an intraindividual variation that may reflect its dependence upon the rates of gastrointestinal absorption and splanchnic-hepatic blood flow, and hence upon the rate of hepatic drug entry.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02336686
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  • 92
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    Comparative bioavailability of a cisapride suppository and tablet formulation in healthy volunteers (1990)
    Springer
    European journal of clinical pharmacology 38 (1990), S. 629-631 
    Details
    ISSN: 1432-1041
    Keywords: Cisapride ; pharmacokinetics ; bioavailability ; suppository ; tablet
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The comparative bioavailability of cisapride as a 30 mg suppository and three 5 mg oral tablets was investigated in 12 non-smoking, healthy male volunteers. The two formulations were administered on two separate occasions following an overnight fast, according to a randomized cross-over design. The plasma concentration of cisapride was measured over 48 h after drug administration. The 30 mg suppository exhibited a mean time to the peak plasma concentration of 3.8 h, while the tablets showed a significantly earlier peak time of 1.5 h. The maximum plasma concentration of cisapride after the 30 mg suppository (50.3 ng · ml−1) was significantly lower than after the tablets (74.3 ng · ml−1). The AUCs following the two treatments did not differ significantly from each other. The comparative bioavailability of the 30 mg cisapride suppository in relation to the three 5 mg oral tablets was 85%, with a 95%-confidence interval of 67% to 102% (not adjusted for dose). Normalizing the mean AUC by dose, the relative bioavailability of the suppository was 43% of that of the tablet. The elimination half-life of cisapride was not significantly different following the administration of the two formulations (9.3 h for the suppository and 9.8 h for the tablet).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00278595
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  • 93
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    Pharmacokinetics of various single intravenous and oral doses of omeprazole (1990)
    Springer
    European journal of clinical pharmacology 39 (1990), S. 195-197 
    Details
    ISSN: 1432-1041
    Keywords: Omeprazole ; metabolites ; bioavailability ; pharmacokinetics ; dose-dependent kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The influence of dose on the kinetics of omeprazole and two of its metabolites, hydroxyomeprazole and the sulphone, has been studied. Ten healthy subjects were given omeprazole 10 and 40 mg iv and 10, 40 and 90 mg orally. No significant dose-related difference in any parameter calculated from the iv experiments was detected. Following the oral solutions, however, there was a dose-dependent increase in systemic availability, probably due to saturable first-pass elimination. The AUC of the sulphone also seemed to increase non-linearly with increasing dose, and that of the hydroxyomeprazole increased in proportion to dose. The slight dose-dependency of the bioavailability of the solution is considered to be of no or limited clinical relevance. Furthermore, since omeprazole is given orally as slowly absorbed enteric coated granules in the dose of 20 mg o.d., the potential for dose-dependent kinetics in clinical practice would be much less than in the present study.
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    URL: http://dx.doi.org/10.1007/BF00280061
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  • 94
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    Pharmacokinetics of oral noscapine (1990)
    Springer
    European journal of clinical pharmacology 39 (1990), S. 275-279 
    Details
    ISSN: 1432-1041
    Keywords: Noscapine ; pharmacokinetics ; bioavailability ; dose dependency ; oral administration ; inter- and intra-individual variability ; adverse events
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The relative bioavailability in 20 healthy volunteers of 100 mg, 200 mg and 300 mg tablets of noscapine and 200 mg as a solution has been assessed in a four-way cross-over study, with repeated administration of the 200 mg dose to assess intraindividual variability. There was a disproportionate increase in the AUC of noscapine tablets, as a 3-fold increase in dose produced a 9-fold rise in AUC. This dose-dependency could mainly be attributed to saturable first-pass metabolism of the drug. Administration of noscapine as a solution resulted in a significantly higher maximal concentration at an earlier time-point and a higher AUC than the corresponding dose as tablets. Repeated administration of noscapine tablets and solution yielded higher AUC on the second dosing occasion. No cause for this carry-over effect was found, and the contribution of remaining noscapine was negligible. The terminal half-life of noscapine, which was independent of formulation or dose size was 4.5 h. Both inter- and intraindividual variability in noscapine kinetics were very high, e.g. 73% and 51% CV of the AUC for the 200 mg tablet.
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    URL: http://dx.doi.org/10.1007/BF00315110
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  • 95
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    Yohimbine bioavailability in humans (1990)
    Springer
    European journal of clinical pharmacology 39 (1990), S. 409-411 
    Details
    ISSN: 1432-1041
    Keywords: yohimbine ; pharmacokinetics ; bioavailability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Pharmacokinetic profiles were determined in seven healthy young male subjects following single oral and intravenous doses of 10 mg of yohimbine hydrochloride. The drug was rapidly eliminated (t1/2β 0.58 h orally and t1/2β 0.68 h intravenously). Following intravenous administration the data fit a two-compartment pharmacokinetic model, with a very rapid distribution phase (t1/2a was approximately 6 min). Both the oral and the intravenous yohimbine clearance values were high but oral clearance values were much higher (mean 9.77 ml·min−1·kg−1 intravenous versus 55.9 ml·min−1·kg−1 oral). The oral bioavailability showed great variability, ranging from 7% to 87% (mean value was 33%). The imcomplete oral bioavailability of yohimbine may reflect either incomplete absorption from the gastrointestinal tract or an hepatic first pass effect. Although yohimbine is rapidly absorbed when given orally, the bioavailability is quite variable and considerable individualization of dosing may be necessary when the drug is used orally for clinical indications.
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    URL: http://dx.doi.org/10.1007/BF00315421
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  • 96
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    Stereoselective disposition of carvedilol in man after intravenous and oral administration of the racemic compound (1990)
    Springer
    European journal of clinical pharmacology 38 (1990), S. S108 
    Details
    ISSN: 1432-1041
    Keywords: carvedilol ; enantiomer pharmacokinetics ; bioavailability ; first-pass effect
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The racemic compound carvedilol is a multiple-action oral antihypertensive drug that exhibits both vasodilator and non-selective beta-adrenergic blocking activities. The effects of the levorotatoryS-enantiomer [S( − )-CARV] are vasodilatation and beta-blockade. TheR (+)-enantiomer [R (+)-CARV] is a pure vasodilating agent. Quantitative determination of the enantiomers in human plasma by HPLC was carried out after formation of diastereoisomers with the chiral reagent 2,3,4,6-tetraO-acetyl-β-d-glucopyranosyl isothiocyanate (GITC). The pharmacokinetics of the enantiomers were studied following i. v. (12.5 mg in 1 h) and p. o. (50 mg) administration of racemic carvedilol in ten healthy male subjects according to a randomized crossover design. The AUCs ofS (−)-CARV were significantly lower than those ofR (+)-CARV after both i. v. and p. o. administration. The systemic clearance of the two enantiomers was significantly different, whereas half-lives and apparent distribution volumes were comparable. Following p. o. administration, the absolute bioavailability (31.1% and 15.1%, respectively) and maximal plasma concentrations ofR (+ )-CARV were twice those ofS (−)-CARV A similar difference was found in the half-lives. A close correlation existed between enantiomeric ratios after i.v. and after p. o. administration, demonstrating slight intraindividual variability. The preferential systemic clearance of theS ( − )-enantiomer suggests stereoselective hepatic metabolism of carvedilol, becoming especially apparent after p. o. administration. The small intrasubject variability in enantiomer ratios indicates a relatively constant relation of beta-blockade to vasodilation during chronic treatment.
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    URL: http://dx.doi.org/10.1007/BF01409476
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  • 97
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    Comments on two recent deconvolution methods (1990)
    Springer
    Journal of pharmacokinetics and pharmacodynamics 18 (1990), S. 483-489 
    Details
    ISSN: 1573-8744
    Keywords: linear system theory ; convolution ; numerical deconvolution ; mathematical modeling ; bioavailability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract In a recent paper Vajda et al. presented a deconvolution method based on the assumptions that the response of a system and the input function to a system are described by first- order linear processes. The method is similar to one proposed by Veng- Pedersen, and obtains similar results. In this article a simpler, not new, and now generally available method for this special use is considered to point out potential risks associated with all three deconvolution methods.
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    URL: http://dx.doi.org/10.1007/BF01061706
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  • 98
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    Effect of dietary fibres on bioavailability of vitamin A and thiamine (1990)
    Springer
    Plant foods for human nutrition 40 (1990), S. 259-265 
    Details
    ISSN: 1573-9104
    Keywords: dietary fibre ; bioavailability ; vitamin A ; thiamine ; serum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Different sources of dietary fibre (cellulose, pectin, Isabgol, cabbage and guava) were fed to weaning rats for 5 weeks to study their effect on serum vitamins. Both the plant foods (cabbage and guava) were analysed for dietary fibre. Guava was found to be a good source of dietary fibre constituting 51.77% of dry pulp, whereas cabbage contained only 16.17%. Cellulose was the major component of dietary fibre in both the plant foods. The concentration of vitamin A and thiamine in the serum of fibre-fed rats was significantly lower than that of rats on a fibre-free diet. However, the amount of vitamin A in serum decreased significantly with the increase in level of dietary fibre, but the decrease was non-significant in the case of thiamine.
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    URL: http://dx.doi.org/10.1007/BF02193849
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  • 99
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    Ascorbate-2-sulfate as a dietary vitamin C source for atlantic salmon (Salmo salar): 1. Growth, bioactivity, haematology and humoral immune response (1990)
    Springer
    Fish physiology and biochemistry 8 (1990), S. 419-427 
    Details
    ISSN: 1573-5168
    Keywords: Atlantic salmon ; fish nutrition ; vitamin C ; megadoses ascorbate ; ascorbate-2-sulfate ; bioavailability ; vitamin C deficiency ; growth ; humoral immune response ; haematology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The present experiment shows that ascorbate-2-sulfate (AS) is not equivalent to ascorbic acid (AA) as a dietary vitamin C source for Atlantic salmon (Salmo salar). Within reasonable feed supplemental levels AS does not provide the tissues with adequate supplies of vitamin C to secure optimal physiological functions as demonstrated by biochemical and haematological analyses. AS could not be detected in the liver of fish fed either AA or AS, nor in vitamin C — deprived salmon, suggesting that AS is not the natural storage form of vitamin C in this species. There were no significant differences in antibody production against a soluble artificial antigen (NIP11-LPH) in fish fed 500 and 5000 mg AA/Kg dry diet or equivalent amounts of AS during a period of six weeks at a water temperature of 7.2°C.
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    URL: http://dx.doi.org/10.1007/BF00003398
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  • 100
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    Formulation and in Vitro-in Vivo Evaluation of Sustained-Release Lithium Carbonate Tablets (1990)
    Springer
    Pharmaceutical research 7 (1990), S. 359-363 
    Details
    ISSN: 1573-904X
    Keywords: lithium ; sustained release ; pharmacokinetics ; bioavailability ; in vitro
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The release of lithium carbonate incorporated into polymethylmethacrylate, poly vinyl chloride, hy-drogenated vegetable oil, and carbomer matrix tablets was studied in vitro. The formulation containing 10% carbomer showed a sustained-release profile comparable to that of a standard, commercially available, sustained-release preparation containing 400 mg lithium carbonate embedded in a composite material. In vivo the newly formulated and standard sustained-release lithium carbonate tablets were compared to an oral solution and conventional lithium carbonate tablets in 12 healthy subjects. These crossover studies showed that the sustained-release tablets produced a flatter serum concentration curve than the oral solution and conventional tablet, without loss of total bioavailability.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1015863204732
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