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  • Articles  (223)
  • bioavailability  (223)
  • Springer  (223)
  • American Association for the Advancement of Science
  • Cell Press
  • Oxford University Press
  • 2005-2009
  • 1985-1989  (93)
  • 1980-1984  (130)
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  • Articles  (223)
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  • Springer  (223)
  • American Association for the Advancement of Science
  • Cell Press
  • Oxford University Press
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  • 1
    Electronic Resource
    Electronic Resource
    Zur Bioverfügbarkeitsprüfung von Mikronährstoffen (1989)
    Springer
    European journal of nutrition 28 (1989), S. 130-141 
    Details
    ISSN: 1436-6215
    Keywords: bioavailability ; folic acid ; pharmaceutical preparation ; Bioverfügbarkeit ; Folsäure ; Arzneimittelzubereitung
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Medicine
    Description / Table of Contents: Zusammenfassung Untersuchungen zur Bioverfügbarkeit essentieller Mikronährstoffe (Vitamine, Mineralstoffe, Spurenelemente) aus Lebensmitteln wie auch aus Arzneimittelzubereitungen sind von entscheidender Bedeutung bei der Beurteilung des jeweiligen Beitrages zur Nährstoffversorgung bzw. zur Abschätzung eines möglichen Therapieerfolges. Die Durchführung derartiger Prüfungen erfolgt in der Praxis nicht selten nach unterschiedlichen Kriterien. Deshalb werden zunächst die Grundsätze erläutert, die bei entsprechenden Prüfungen für eine valide Bewertung von Nähr- bzw. Wirkstoffgemischen oder Monopräparaten bedeutsam sind. Abschließend wird die Ermittlung der Bioverfügbarkeit von Folsäure an einem Beispiel demonstriert. Zur Testung werden die postresorptiven Kurvenintegrale ermittelt, wobei die Daten auf das basale Ausgangsniveau bezogen werden. Zur Beurteilung der Bioverfügbarkeit findet neben dem maximalen Vitaminanstieg im Serum sowie der Zeit bis zum Konzentrationsmaximum insbesondere der Bioverfügbarkeitsquotient von Test- und Referenzzubereitung mit seinem 95%-VB Berücksichtigung. Die Ergebnisse zeigen, daß die exemplarisch eingesetzte Testsubstanz, 5-Formyl-Tetrahydrofolsäure, eine sehr gute Bioverfügbarkeit aufweist und daß unter Anwendung der beschriebenen Rahmenbedingungen eine objektive Bewertung der Bioverfügbarkeit möglich ist.
    Notes: Summary Bioavailability studies of micronutrients (vitamins, minerals) from different food stuffs, as well as from pharmaceutical preparations are of great importance for the calculation of nutrient intake and/or the evaluation of the therapeutic value. In practice, bioavailability studies are not generally performed on a standardized level. For this reason basic criterions are presented and discussed. Finally, the investigation of the bioavailability of folate is demonstrated by an example. The parameters investigated are: the maximal concentration (cmax), the time to reach this maximum (tmax), and especially the bioavailability ratio determined from the area under the curve (AUC) after administration of the folic acid containing test and reference preparation. The results indicate that 5-formyl-tetrahydrofolic acid given in the tested form has nearly the same bioavailability (ratio: 1.02) as folic acid (pteroylmonoglutamic acid) in aqueous solution.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02030128
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  • 2
    Electronic Resource
    Electronic Resource
    Effects on cimetidine bioavailability of metoclopramide and antacids given two hours apart (1989)
    Springer
    European journal of clinical pharmacology 37 (1989), S. 409-410 
    Details
    ISSN: 1432-1041
    Keywords: cimetidine ; metoclopramide ; antacids ; absorption ; bioavailability ; drug interaction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Plasma cimetidine levels were determined in 9 normal subjects after a single oral dose of cimetidine 400 mg under control conditions, 2 h before metoclopramide 20 mg and 2 h after a potent antacid. The bioavailability of cimetidine was not significantly affected by metoclopramide and it was marginally reduced by the antacid.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00558511
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  • 3
    Electronic Resource
    Electronic Resource
    Bioavailability of suckable tablets of oral N-acetylcysteine in man (1989)
    Springer
    European journal of clinical pharmacology 37 (1989), S. 419-421 
    Details
    ISSN: 1432-1041
    Keywords: N-Acetylcysteine ; oral administration ; bioavailability ; healthy subjects ; suckable formulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The pharmacokinetics and bioavailability of suckable tablets and granules of N-acetylcysteine (NAC) have been compared after oral administration of 400 mg doses to 10 healthy volunteers. The oral bioavailability of the NAC tablets was 103%. In a multiple dosing study of the same tablets in the same subjects, a high maintenance plasma level of NAC was revealed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00558514
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  • 4
    Electronic Resource
    Electronic Resource
    Effect of food on the absorption and pharmacokinetics of prednisolone from enteric-coated tablets (1989)
    Springer
    European journal of clinical pharmacology 37 (1989), S. 423-426 
    Details
    ISSN: 1432-1041
    Keywords: prednisolone ; food intake ; enteric-coated tablets ; pharmacokinetics ; bioavailability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Prednisolone absorption and bioavailability of 10 mg enteric-coated (EC) and plain (uncoated) tablets were investigated after fasting and heavy meals (EC only) consumed to satiety in normal healthy volunteers. The same volunteers had also received 16 mg of prednisolone intravenously. In fasted subjects, the absolute bioavailability fraction, as normalised for intravenous doses, of prednisolone from plain tablets was 1.055 and from EC tablets was 0.996. The peak concentrations after plain and EC tablets were 309 and 249 ng/ml attained at 0.98 and 5.14 h, respectively. The means plasma elimination half-lives following the plain, EC tablets and intravenous administration in fasting conditions were 3.73, 3.89 and 3.78 h, respectively. Food interfered with both the absorption and the pharmacokinetics of prednisolone after EC tablets resulting in variability in its plasma levels. In some cases absorption of prednisolone was delayed for 12 h and remained at a measurable level for 24 h. In other cases, a normal absorption pattern was observed. This inter- and intrasubject variability of the effect of food appears to be related to its quantity, constituents and also the subjects physiological characteristics. It is concluded that enteric-coated prednisolone tablets should be administered at least 2 h between meals. However, for more predictable corticosteroid absorption (perhaps thus avoiding the therapeutic failure), plain prednisolone tablets are preferable.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00558515
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  • 5
    Electronic Resource
    Electronic Resource
    Pharmacokinetic properties and clinical efficacy of once-daily sustained-release naproxen (1989)
    Springer
    European journal of clinical pharmacology 36 (1989), S. 383-388 
    Details
    ISSN: 1432-1041
    Keywords: naproxen ; sustained-release formulation ; pharmacokinetics ; bioavailability ; efficacy ; tolerability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The pharmacokinetics and clinical efficacy of a once-daily sustained-release formulation of naproxen (sodium salt) have been compared with those of conventional-release agents. In a single dose pharmacokinetic study, the rate of absorption of the sustained-release preparation was less than that of a conventional-release preparation but the extent of absorption was the same. As is the case with conventional-release naproxen, food decreased the rate but not the extent of absorption of the sustained-release formulation. On multiple dose administration for 7 days, the AUC and average concentrations of the sustained release preparation (1 g daily) were the same as those for conventional release preparations of naproxen sodium (250 mg four times daily) and naproxen free acid (500 mg daily). The conventional-release sodium salt was absorbed more quickly with no differences in bioavailability. A double-blind clinical comparison in patients with osteoarthritis showed the sustained-release preparation (1 g daily) to be equivalent in efficacy to conventional naproxen capsules (500 mg twice daily) but to have a significantly lower incidence of gastrointestinal side-effects. The results suggest that sustained-release naproxen sodium has potential for use as a once-daily treatment for inflammatory disease.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00558300
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  • 6
    Electronic Resource
    Electronic Resource
    Pharmacokinetic characterization of the antiarrhythmic drug diprafenone in man (1989)
    Springer
    European journal of clinical pharmacology 37 (1989), S. 313-316 
    Details
    ISSN: 1432-1041
    Keywords: diprafenone ; pharmacokinetics ; bioavailability ; first-pass metabolism ; healthy volunteers
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The pharmacokinetics of the antiarrhythmic drug diprafenone have been investigated in 6 healthy volunteers following single intravenous (50 mg) and oral doses (50 and 150 mg). Diprafenone was mainly eliminated by metabolism in the liver. Following i.v. infusion of 50 mg diprafenone, the terminal half-life of elimination was 1.50 h, the volume of distribution at steady-state was 1.23 l·kg−1, and the free fraction in plasma was 1.68%. Mean total plasma clearance was 741 ml·min−1·70 kg−1, which approaches normal liver blood flow after correction for the blood/plasma concentration ratio. Thus, diprafenone can be classified as a high extraction drug. Following oral administration, a dose-dependent increase in bioavailability from 10.9 (50 mg dose) to 32.5% (150 mg dose) was observed. The data suggest that diprafenone is subject to saturable hepatic first-pass metabolism.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00679792
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  • 7
    Electronic Resource
    Electronic Resource
    Influence of hyperlipidic food on the kinetics of slow-release formulations of theophylline (1989)
    Springer
    European journal of clinical pharmacology 37 (1989), S. 85-90 
    Details
    ISSN: 1432-1041
    Keywords: theophylline ; sustained-release formulation ; bioavailability ; fatty food ; dumping effect ; pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary A cross-over study of kinetics has been undertaken in 12 healthy adults volunteers using two sustained-release theophylline products that allow once a day dosing (Theo-Dur tablets and Dilatrane A.P. bead filled capsules) to compare the i.v. pharmacokinetic profiles when taken with an hyperlipidic meal and a balanced standard meal. Each subject took part in four phases in randomised order, corresponding to all possible combinations of the products and the types of meal. Each phase involved a single dose of 9 to 11 mg·kg−1 theophylline administered at 20.00 h, at the beginning of the meal, with 100 ml water. The two formulations were found to be bioequivalent with both types of meal. Taken with a balanced meal, the mean parameters were similar; for Theo-Dur and Dilatrane A.P. they were respectively: Cmax: 11.32 mg·l−1 which plateaued from 8 to 10 h after dosing and 10.9 mg·l−1, which plateaued after 6 to 10 h; AUC 230 mg·h·l−1 and 220 mg·h·l−1; and MRT 18.2 h and 17.7 h. After the hyperlipidic meal the values for Theo-Dur and Dilatrane A.P. respectively, were: Cmax 10.9 mg·l−1 at 12 h and 11.3 mg·l−1 at 10 h; AUC 237 mg·h·l−1 and 227 mg·h·l−1; and MRT 19.2 h and 18.9 h. In spite of a decrease in the absorption rate, which led to a shift to the right of about 2 h of the plasma concentration-time curve, the bioavailability of both formulations were not significantly modified by a hyperlipidic meal as compared to a balanced meal. The shift of the curve with fatty food was not clinically important, as there was no dumping effect. The main difference between the two formulations was seen during the absorption phase, which was linear and less variable with Dilatrane A.P. and sigmoidal with Theo-Dur. This was observed with both types of meal.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00609431
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  • 8
    Electronic Resource
    Electronic Resource
    Performances of three bacterial assays in toxicity assessment (1989)
    Springer
    Hydrobiologia 188-189 (1989), S. 149-153 
    Details
    ISSN: 1573-5117
    Keywords: bacterial assays ; toxicity assessment ; microtox test ; oxygen consumption assay ; glucose mineralization assay ; bioavailability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Three differing bacterial toxicity assays were compared: the ‘Microtox’ test, (Photobacterium phosphoreum luminescence inhibition assay), the ‘oxygen consumption of activated sludge’ assay (ISO 8192), and the ‘Glucose U-14C mineralization’ assay (the rate of release of 14CO2 by ‘Escherichia coli’ ). Metals, amines, halogenated alcans, chlorophenols, aromatic hydrocarbons, surfactants, and pesticides were screened for their toxic activity. Results showed satisfactory repeatability of the three bacterial assays with variation coefficients between 5 and 32%. The ‘Microtox’ assay was the most sensitive test evaluated under our conditions. The lower sensitivity of the ‘oxygen consumption’ assay may have been due to high concentrations of substrates which modify toxicant bioavailability, and also to a high biomass/toxic substances ratio. The ‘Glucose U-14C mineralization’ assay was selective, and low in sensitivity; but the specific species used in this test — Escherichia coli — may have been responsible for this selectivity. The ‘Microtox’ test appears to be well adapted to the detection of aquatic environmental pollution, and to the toxicity screening of complex solid waste effluents and/or leachates. The ‘oxygen consumption’ assay can be advantageously used to measure the impact of sewage on activated sludge in biological treatment plants. The ‘Glucose U-14C mineralization’ assay, which does not require high biomass, can be useful for in situ studies using field microorganisms.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00027780
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  • 9
    Electronic Resource
    Electronic Resource
    Bioavailable metal uptake rate in urban stormwater determined by dialysis with receiving resins (1989)
    Springer
    Hydrobiologia 176-177 (1989), S. 491-495 
    Details
    ISSN: 1573-5117
    Keywords: metal uptake ; dialysis with receiving resins ; bioavailability ; urban stormwaters
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Bioavailable metal uptake rates have been determined in urban stormwater by dialysis with receiving resins. Values at outfalls reflect the sporadic and variable nature of discharges of bioavailable metals with stormwater. Variations in the uptake rates may be explained in terms of hydrochemical processes affecting bioavailable metal mobilisation and transport in the stormwater system, including rainfall volume, rainfall acidity and gullypot interstitial water mobilisation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00026584
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  • 10
    Electronic Resource
    Electronic Resource
    The effect of heavy metal speciation in sediment on bioavailability to tubificid worms (1989)
    Springer
    Hydrobiologia 188-189 (1989), S. 487-496 
    Details
    ISSN: 1573-5117
    Keywords: heavy metals ; sediment ; speciation ; bioavailability ; tubificid worms
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The bioavailability of heavy metals in sediment to freshwater tubificid worms was compared with measures of chemical extractability using a sequential extraction procedure. In order to provide a range of test sediments of different quality, various mineral phases were prepared, in which the metals were spiked by adsorption or coprecipitation and these were then mixed with a bulk base sediment in known proportions. Results indicated good correlation between worm metal burden and metal mobilised from the sediments in the first (‘exchangeable’) sequential extraction step for Cd, Cu and Pb. Of the other metals tested, Zn levels in the worms were found to be constant, suggesting regulation, and Ni uptake was too small for accurate measurement. In general, metals spiked to the sediment directly, or adsorbed on the clay mineral phase were found to be much more available than those bound to sewage sludge, carbonate or hydrous ferric oxide phases.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00027816
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  • 11
    Electronic Resource
    Electronic Resource
    Preliminary investigations on the influence of suspended sediments on the bioaccumulation of two chlorobenzenes by the guppy (Poecilia reticulata) (1989)
    Springer
    Hydrobiologia 188-189 (1989), S. 573-576 
    Details
    ISSN: 1573-5117
    Keywords: bioavailability ; bioaccumulation ; hydrophobicity ; fish ; chlorobenzenes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In this study the uptake by guppies (Poecilia reticulata) of 1,2,3-trichlorobenzene (TCB) and hexachlorobenzene (HCB) from sediment-free water was compared with uptake in the presence of suspended sediment. The results show that the influence of suspended sediment on the uptake of chlorobenzenes varies with test compound. For TCB uptake was not influenced by the presence of suspended sediment. This is probably due to the large amount of the chemical which is dissolved relative to the amount which is present in the sorbed state. For the more hydrophobic HCB, the concentration found in the fish from the system with suspended sediment was significantly higher than in fish from the control experiment.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00027825
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  • 12
    Electronic Resource
    Electronic Resource
    A collaborative study of methods of protein evaluation: introductory paper (1989)
    Springer
    Plant foods for human nutrition 39 (1989), S. 3-11 
    Details
    ISSN: 1573-9104
    Keywords: protein quality ; amino acids ; digestibility ; bioavailability ; rats ; in vitro enzyme assays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The USDA's collaborative study of methods of protein quality evaluation is introduced. It was intended primarily to provide a basis for the evaluation of possibly improved procedures for the labelling of foods as a source of dietary protein. In general, the usefulness of in vitro digestibility procedures has been confirmed, but problems remained for the in vitro evaluation of heat-damaged materials and of some types of pinto beans.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01092396
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  • 13
    Electronic Resource
    Electronic Resource
    Bioavailability of tryptophan in selected foods by rat growth assay (1989)
    Springer
    Plant foods for human nutrition 39 (1989), S. 85-91 
    Details
    ISSN: 1573-9104
    Keywords: protein quality ; amino acids ; rats ; bioavailability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Tryptophan bioavailabilities were estimated in 16 protein sources using 10 day rat growth assays with casein as the reference protein. Growth responses of rats fed test food diets were compared to growth responses of rats fed basal diets with graded levels of tryptophan ranging from 50 to 100 mg of tryptophan/100 g diet. Estimates of tryptophan availabilities were 85–100% for all products except whole wheat cereal (73%) and pinto beans (59%). Results of a previous study on lysine availability indicated that poor response to pinto beans was due either to poor digestibility or to the presence of some unidentified growth inhibitor.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01092405
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  • 14
    Electronic Resource
    Electronic Resource
    Application of Mean Residence-Time Concepts to Pharmacokinetic Systems with Noninstantaneous Input and Nonlinear Elimination (1989)
    Springer
    Pharmaceutical research 6 (1989), S. 4-12 
    Details
    ISSN: 1573-904X
    Keywords: mean residence time ; moment analysis ; Michaelis–Menten elimination ; compartmental models ; bioavailability ; mean absorption time
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Equations describing the mean residence time (MRT) of drugs in the body are derived for drugs that are administered by first-and zero-order rates into systems with Michaelis–Menten elimination. With computer simulations, the validity of these equations, the differences between them, and the conventional approach using the AUMC/AUC or the summation of mean times are demonstrated by examining calculations of the percentage of the administered dose eliminated at the MRT and AUMC/AUC. The effects of the absorption rate on the AUC and on the approximate and true MRT values in a nonlinear pharmacokinetic system are also illustrated with computer simulations. It was previously found that the true MRTiv = V ss · AUCiv/dose for an iv bolus. The total MRT (sum of input and disposition) of a drug after noninstantaneous administration was found to be a function of the MRTiv, two values of AUC (iv and non-iv), and exactly how the drug is administered expressed as the mean absorption time (MAT). In addition, a theoretical basis is proposed for calculation of the bioavailability of drugs in both linear and nonlinear pharmacokinetic systems.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1015883131875
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  • 15
    Electronic Resource
    Electronic Resource
    Correlation of Phenylpropanolamine Bioavailability with Gastrointestinal Transit by Scintigraphic Monitoring of 111In-Labeled Hydroxypropylmethylcellulose Matrices (1989)
    Springer
    Pharmaceutical research 6 (1989), S. 274-278 
    Details
    ISSN: 1573-904X
    Keywords: bioavailability ; scintigraphy ; gastrointestinal transit ; controlled release ; phenylpropanolamine ; hydroxypropylmethylcellulose
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Two controlled-release hydroxypropylmethylcellulose (HPMC) matrix formulations, a single-unit and a multiple-unit system, have been evaluated in human volunteers. Both formulations contained the sympathomimetic drug phenylpropanolamine hydrochloride and each was radiolabeled with 111Inbound Amberlite IR 120 ion-exchange resin. The formulations were administered to each of six healthy male volunteers and gastrointestinal (GI) transit was monitored using a gamma camera. Serum samples were taken at set time intervals and assayed for phenylpropanolamine content, thus allowing blood drug levels to be correlated with the position of the dosage form in the GI tract. The multiple-unit system emptied from the stomach gradually over a period of about 180 min, when administered after a light breakfast, whereas the single-unit dosage forms had extremely variable gastric emptying times (range, 60 to 〉570 min). However, both formulations provided prolonged phenylpropanolamine blood levels. The differences in the blood profiles obtained with the two formulations were attributed to variations in their in vitro release rates and not to any differences in their GI transit times.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1015986121822
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  • 16
    Electronic Resource
    Electronic Resource
    Enhanced Bioavailability of Subcutaneously Injected Insulin Coadministered with Collagen in Rats and Humans (1989)
    Springer
    Pharmaceutical research 6 (1989), S. 813-816 
    Details
    ISSN: 1573-904X
    Keywords: insulin ; collagen ; injection ; subcutaneous injection ; bioavailability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The present study was undertaken to develop an agent that stabilizes insulin injected subcutaneously. 125I-Porcine insulin with 0.2 U/kg unlabeled porcine insulin was subcutaneously injected with or without collagen in the rat under the depilated skin of the back. At various times, the radioactivity in subcutaneous tissue was assayed for insulin and its metabolites by gel filtration. The degradation and absorption rate constants of insulin at the subcutaneous injection site were estimated according to a one-compartment model. The degradation rate constant of insulin in the presence of collagen at the injection site was less than half of the control rate. The inhibition was confirmed by increases in the immunoreactive insulin plasma levels and the hypoglycemic effect in rats and healthy volunteers. We postulate that collagen prevents insulin from being degraded by inhibiting proteolytic enzymes, mainly collagenase-like peptidase, in subcutaneous tissue.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1015987800808
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  • 17
    Electronic Resource
    Electronic Resource
    Estimation of Bioavailability on a Single Occasion After Semisimultaneous Drug Administration (1989)
    Springer
    Pharmaceutical research 6 (1989), S. 817-821 
    Details
    ISSN: 1573-904X
    Keywords: bioavailability evaluation ; absorption ; intraindividual variability ; bioavailability ; intraperitoneal ; lithium pharmacokinetics in rats
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A method for determination of absorption rate and bioavailability was developed to reduce the influence of intraindividual variability and applied to the absolute intraperitoneal availability of lithium in the rat. In this method the test and the reference doses are given with a few hours' interval, and the resulting concentration–time data are analyzed by nonlinear regression. The bioavailability estimation by this approach was compared to that of the traditional method, with test and reference doses given on separate days. The mean estimates of availability were 1.035 ± 0.109 (N = 7) and 0.984 ± 0.052 (N = 11) for the traditional and the alternative method, respectively. Thus, the precision was better in the latter. Major influences of dose- or time-dependent kinetics of lithium on the availability estimates were excluded by the design used. The estimation of bioavailability was robust with respect to the choice of absorption and disposition model and the duration of sampling. The plasma clearance of lithium was 169 ± 15 ml/hr/kg, with a terminal half-life of 5.0 ± 0.5 hr (N = 5).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1015939917646
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  • 18
    Electronic Resource
    Electronic Resource
    Pharmacokinetics and bioavailability of reduced and oxidized N-acetylcysteine (1988)
    Springer
    European journal of clinical pharmacology 34 (1988), S. 77-82 
    Details
    ISSN: 1432-1041
    Keywords: N-acetylcysteine ; pharmacokinetics ; bioavailability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The pharmacokinetics and bioavailability of N-acetylcysteine (NAC) have been determined after its intravenous and oral administration to 6 healthy volunteers. According to a randomized cross-over design each subject received NAC 200 mg i.v. and 400 mg p.o., and blood samples were collected for 30 h. Reduced NAC had a volume of distribution (VSS) of 0.59 l·kg−1 and a plasma clearance of 0.84 l·h−1·kg−1. The terminal half-life after intravenous administration was 1.95 h. The oral bioavailability was 4.0%. Based on total NAC concentration, its volume of distribution (VSS) was 0.47 l·kg−1 and its plasma clearance was 0.11 l·h−1·kg−1. The terminal half-life was 5.58 h after intravenous administration and 6.25 h after oral administration. Oral bioavailability of total NAC was 9.1%.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01061422
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  • 19
    Electronic Resource
    Electronic Resource
    Increased systemic availability of albendazole when taken with a fatty meal (1988)
    Springer
    European journal of clinical pharmacology 34 (1988), S. 315-317 
    Details
    ISSN: 1432-1041
    Keywords: albendazole ; echinococcosis ; bioavailability ; food intake ; fatty meal
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary We have studied the systemic availability of oral albendazole in 6 patients with echinococcosis either fasting or with breakfast. Albendazole sulphoxide, the pharmacologically active principle, was assayed by HPLC. Mean plasma concentrations and AUCs were 4.5 times higher when albendazole was given with breakfast than when administered in the fasting state. We conclude that therapy of echinococcosis with albendazole requires the drug to be taken with meals and that administration on an empty stomach might be more appropriate when intraluminal effects are desired, e.g. for intestinal parasites.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00540964
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  • 20
    Electronic Resource
    Electronic Resource
    Pharmacokinetics of xamoterol after intravenous and oral administration to volunteers (1988)
    Springer
    European journal of clinical pharmacology 34 (1988), S. 469-473 
    Details
    ISSN: 1432-1041
    Keywords: xamoterol ; cardiac failure ; beta1-adrenoceptor partial agonist ; pharmacokinetics ; bioavailability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The pharmacokinetics of xamoterol, a β-adrenoceptor partial agonist under clinical evaluation for the treatment of mild to moderate heart failure, have been studied in 12 healthy male subjects. They received 14 mg i.v. and oral doses of 50 and 200 mg as a tablet and 200 mg as a solution in a 4 way cross-over design. After i.v. dosing the elimination half-life was 7.7 h, the total body clearance was 224 ml·min−1 and the volume of distribution at steady-state (Vss) was 48 l. Sixty-two percent of the dose was recovered unchanged in urine. After oral doses, the absolute bioavailability of xamoterol was shown to be 5% irrespective of whether the dose was administered as a tablet or solution. Peak plasma concentrations occurred at about 2 h for the tablet dose and slightly earlier (1.4 h) for the solution. Peak plasma concentration, AUC and urinary recovery of unchanged drug increased in proportion to dose. The apparent elimination half-life after oral doses (16 h) was significantly longer than that observed after an intravenous dose. Despite the low bioavailability, the degree of inter-subject variability of oral bioavailability was small probably indicating that the controlling factor is the hydrophilic nature of the molecule rather than extensive first pass metabolism or poor dissolution of xamoterol from the tablet formulation.
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    URL: http://dx.doi.org/10.1007/BF01046704
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    Lack of effect of a single-dose of sulglicotide on the bioavailability of diclofenac (1988)
    Springer
    European journal of clinical pharmacology 34 (1988), S. 211-212 
    Details
    ISSN: 1432-1041
    Keywords: diclofenac ; sulglicotide ; bioavailability ; drug interaction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The bioavailability of diclofenac (D) was assessed in 12 healthy volunteers treated orally with single doses of 100 mg (retard formulation) and subsequently retreated with the same dose of (D) plus sulglicotide (S) 200 mg. (D) blood levels were measured by GLC in samples collected after 1, 2, 4, 6, 8, 12, 24 h. No relevant difference was seen in (D) bioavailability after (S) administration; after 8 h plasma levels of (D) were slightly higher after (S) (p〈0.05), but this difference can be considered incidental only. Thus, sulglicotide does not interfere with the bioavailability of diclofenac, and can be administered concurrently with the latter to prevent possible gastric injury by the antiinflammatory drug.
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    URL: http://dx.doi.org/10.1007/BF00614561
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    Doxazosin in patients with hypertension (1988)
    Springer
    European journal of clinical pharmacology 35 (1988), S. 21-24 
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    ISSN: 1432-1041
    Keywords: doxazosin ; hypertension ; alpha-adrenergic blockade ; bioavailability ; pharmacokinetics ; adverse effects
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The antihypertensive effects and steady-state pharmacokinetics of doxazosin, as well as the bioequivalence of four dosage forms, were studied in 25 hypertensive patients. For an 8 mg daily dose mean Cmax at steady-state for all patients was 108 ng/ml; the mean tmax was 1.8 h. The mean terminal elimination half-life was 22 h. The four tablets containing 1, 2, 4, or 8 mg of doxazosin were bioequivalent in delivering the 8 mg dose. In patients with mild to moderate hypertension, 26-day treatment with doxazosin resulted in blood pressure reduction of 10/7 mm Hg in the supine and 13/18 mm Hg in the standing position. Adverse effects were generally mild and of brief duration.
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    Pharmacokinetics of bolus intravenous and oral doses of L-carnitine in healthy subjects (1988)
    Springer
    European journal of clinical pharmacology 35 (1988), S. 69-75 
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    ISSN: 1432-1041
    Keywords: L-carnitine ; pharmacokinetics ; intravenous and oral doses ; bioavailability ; healthy volunteers
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The pharmacokinetics of single intravenous and oral doses of L-carnitine 2 and 6 g was studied in 6 healthy subjects on a low-carnitine diet. Carnitine was more rapidly eliminated from plasma after the 6 g dose. Comparing the doses, the t1/2β of the elimination phase (β) was 6.5 h vs 3.9 h, the elimination constant 0.40 vs 0.50 h−1 and the plasma carnitine clearance was 5.4 vs 6.11 · h−1 for the 2 g and 6 g doses, respectively, showing dose-related elimination. Saturable kinetics were not found. The apparent volumes of distribution after the two doses were not significantly different and were of the same order as the total body water. Urinary recoveries of the 2 g and 6 g doses were 70% and 82%, respectively, during the first 24 h. Following the oral doses, there was no significant difference between the areas under the plasma carnitine concentration-time curves. Urinary recovery was 8% and 4% for the 2 g and 6 g doses during the first 24 h. Oral bioavailability was 16% for the 2 g dose and 5% for the 6 g dose. The results suggest that the mucosal absorption of carnitine was already saturated by the 2 g dose.
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    Rectal absorption of flecainide acetate (1988)
    Springer
    European journal of clinical pharmacology 35 (1988), S. 89-91 
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    ISSN: 1432-1041
    Keywords: flecainide acetate ; Wolff-Parkinson-White syndrome ; rectal absorption ; suppository ; micro enema ; bioavailability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The rectal absorption of flecainide from an aqueous solution, a fatty suppository and a polyethyleneglycol suppository was studied in one patient with supraventricular tachycardia (Wolff-Parkinson-White syndrome) refractory for oral anti-arrhythmic treatment. Rectal absorption was found to be fast (t1/2abs=1 h) and complete when flecainide was administered as a solution (relative bioavailability 100%). Flecainide was poorly absorbed from a fatty suppository. The polyethyleneglycol suppository gave absorption with a relative bioavailability of 80% and t1/2 abs=1.2 h.
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    Pharmacokinetics of xamoterol after intravenous and oral administration to patients with chronic heart failure (1988)
    Springer
    European journal of clinical pharmacology 35 (1988), S. 183-185 
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    ISSN: 1432-1041
    Keywords: xamoterol ; cardiac failure ; beta1-adrenoceptor partial agonist ; pharmacokinetics ; bioavailability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The pharmacokinetics of xamoterol, a β-adrenergic partial agonist under clinical evaluation for the treatment of mild to moderate heart failure, have been studied in 8 cardiac failure patients (NYHA Class II) of mean age 62 years. After i.v. dosing, the elimination half-life was 7.4±0.4 h, the total body clearance was 228±30 ml·min−1 and the volume of distribution at steady-state was 56±91. 72.5±4.3% of the dose was recovered unchanged in urine. After the oral dose, the absolute bioavailability of xamoterol was shown to be 5.9%. Peak plasma concentrations occurred 1 to 2.5 h after the oral dose. The apparent elimination half-life was significantly longer after oral doses (16±2 h) compared to that observed after an intravenous dose. Renal clearance of xamoterol exceeded glomerular filtration rate as measured by creatinine clearance. The pharmacokinetics of xamoterol in cardiac failure patients with good renal function (creatinine clearance 〉90 ml·min−1) were similar to published data in young healthy male volunteers.
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    URL: http://dx.doi.org/10.1007/BF00609250
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    Pharmacokinetics of ketorolac tromethamine in humans after intravenous, intramuscular and oral administration (1988)
    Springer
    European journal of clinical pharmacology 35 (1988), S. 423-425 
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    ISSN: 1432-1041
    Keywords: ketorolac tromethamine ; non-narcotic analgesic ; pharmacokinetics ; bioavailability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The pharmacokinetics of ketorolac tromethamine, a potent non-narcotic analgesic agent used for relief of moderate to severe pain, has been studied in 15 healthy volunteers who received single 10 mg doses intravenously (i.v.), intramuscularly (i.m.) and orally (p.o.) in a three-way cross-over design. The kinetics of i.v. ketorolac were characterized by a terminal half-life of 5.09 h, a small plasma clearance (CL = 0.35 ml·min−1·kg−1) and a small tissue distribution (Vss=0.111·kg−1, Vβ=0.17 l·kg−1; mean (SD). Following i.m. and p.o. administration, peak levels of approximately 0.8 µg/ml were rapidly attained (tmax = 0.8 and 0.9 h, respectively) and the systemic bioavailability was essentially complete.
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    Pharmacokinetics of intravenous and oral bolus doses of L-carnitine in healthy subjects (1988)
    Springer
    European journal of clinical pharmacology 35 (1988), S. 555-562 
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    ISSN: 1432-1041
    Keywords: L-carnitine ; pharmacokinetics ; intravenous — oral doses ; bioavailability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The pharmacokinetics of single intravenous and oral doses of L-carnitine 2 g and 6 g has been investigated in 6 healthy subjects on a low carnitine diet. Carnitine was more rapidly eliminated from plasma after the higher dose. Comparing the 2-g and 6-g doses, the t1/2β of the elimination phase (β) was 6.5 h vs 3.9 h, the elimination constant was 0.40 vs 0.50 h−1 and the plasma carnitine clearance was 5.4 vs 6.11 × h−1 (p〈0.025), thus showing dose-related elimination. Saturable kinetics was not found in the range of doses given. The apparent volumes of distribution after the two doses were not significantly different and they were of the same order as the total body water. Urinary recoveries after the 2-g and 6-g doses were 70% and 82% during the first 24 h, respectively. Following the two oral dosing, there was no significant difference in AUCs of plasma carnitine. Urinary recoveries were 8% and 4% for the 2-g and 6-g doses during the first 24 h. The oral bioavailability of the 2-g dose was 16% and of the 6 h dose 5%. The results suggest that the mucosal absorption of carnitine is already saturated at the 2-g dose.
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    Bioavailability and pharmacokinetics of oxazepam (1988)
    Springer
    European journal of clinical pharmacology 35 (1988), S. 385-389 
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    ISSN: 1432-1041
    Keywords: oxazepam ; pharmacokinetics ; i.v.-/oral administration ; bioavailability ; healthy volunteers
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Six healthy volunteers received oxazepam 15 mg i.v. and orally at an interval of at least one week. The kinetic variables of i.v. oxazepam were: elimination half-life (t1/2β) 6.7 h, total clearance (CL) 1.07 ml·min−1·kg−1, volume of distribution (Vc) 0.27 l·kg−1 (0.21–0.49) and volume of distribution at steady-state (Vss) 0.59 l·kg−1. The intravenous disposition of unbound oxazepam was characterized by a clearance of 22.5ml·min−1·kg−1 and a distribution volume of 12.3 l·kg−1. After oral oxazepam the peak plasma level was reached in 1.7 to 2.8 h. The plasma t1/2β at 5.8 h was not significantly different from the i.v. value. Absorption was almost complete, with a bioavailability of 92.8%. Urinary recovery was 80.0 and 71.4% of the dose after intravenous and oral administration, respectively. Renal clearance (CLR) of the glucuronide metabolite was 1.10 ml·min−1·kg−1 (0.98–1.52). Oxazepam was extensively bound to plasma protein with a free fraction of 4.5%.
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    The effect of food on the systemic availability of ketoprofen (1988)
    Springer
    European journal of clinical pharmacology 33 (1988), S. 643-645 
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    ISSN: 1432-1041
    Keywords: ketoprofen ; food ; bioavailability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary We have studied the pharmacokinetics of ketoprofen, a non-steroidal anti-inflammatory drug, in 12 patients after a single 100 mg oral dose both in fasting conditions and with a meal. Food significantly affected the peak plasma concentration of ketoprofen and decreased its absorption rate. However, the extent of absorption of ketoprofen, as reflected by the area under the plasma concentration time curve, appeared to be unchanged in the presence of food.
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    Cyclosporin: Pharmacokinetics and detailed studies of plasma and erythrocyte binding during intravenous and oral administration (1988)
    Springer
    European journal of clinical pharmacology 34 (1988), S. 451-460 
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    ISSN: 1432-1041
    Keywords: cyclosporin ; pharmacokinetics ; infusions ; binding ; lipids ; bioavailability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary On the basis that unbound concentration better correlates with response than total plasma or blood concentration, the inter- and intra-subject variability in the distribution of cyclosporin within blood and to plasma components was studied in renal transplant patients. Pharmacokinetic aspects were also studied. Blood samples were analysed from patients who received the drug both by a 72-h i.v. infusion and orally (7 mg·kg−1 twice daily). Steady-state was reached within 18 h of starting the i.v. infusion; the plasma data were best fitted by a biexponential equation with half-times of 0.13–1.02 h and 4.3–13.9 h, associated with the two phases. The mean plasma clearance was 700 ml/min. Concentrations during the infusions measured by RIA and HPLC were comparable. Oral profiles showed rapid and extensive absorption. The peak plasma concentrations were 1460–1880 µg·l−1 and occurred 2–4 h after dosing, with bioavailability estimates of 41–113%. Concentrations measured by RIA were higher than by HPLC. Blood-to-plasma concentration ratio measurements of cyclosporin at 37°C decreased with increasing plasma concentration and increased with haematocrit. Fraction unbound, measured by ultracentrifugation, was in the range 0.042–0.122 with an average of 0.068, and varied little in some patients but showed systematic changes with time in others. Cyclosporin binding was found to be related not only to the triglyceride but, more particularly, to the cholesterol-related lipoproteins in plasma. Monitoring cholesterol may be helpful in identifying patients with extremes in binding or with widely varying binding.
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    The relative systemic availability of ivermectin after administration as capsule, tablet, and oral solution (1988)
    Springer
    European journal of clinical pharmacology 35 (1988), S. 681-684 
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    ISSN: 1432-1041
    Keywords: ivermectin ; bioavailability ; pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Administration of 12-mg doses of ivermectin (H2B1a) to 12 healthy volunteers in the form of tablets, capsules, and alcoholic oral solution showed the solution to have approximately twice the systemic availability as either of the solid forms, as evidence both by the maximum concentrations of drug attained in plasma and by the corresponding areas under the plasma concentration vs time curves. However, the two solid formulations showed similar systemic availability.
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    Bioavailability assessment and pharmacologie response: Impact of first-pass loss when both drug and metabolites are active (1988)
    Springer
    Journal of pharmacokinetics and pharmacodynamics 16 (1988), S. 573-593 
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    ISSN: 1573-8744
    Keywords: bioavailability ; drug ; metabolite ; first-pass hepatic loss ; pharmacologic response ; estimation ; bioequivalence
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Many drugs with low oral bioavailability due to substantial first-pass hepatic loss form pharmacologically active metabolites. In such cases, the pharmacologic activity after oral administration is greater than anticipated from bioavailability data, based on chemical assay of drug alone. This paper explores the use and meaning of pharmacologic data to assess bioavailability under these circumstances. Two steady-state concepts are introduced: a metabolite-to-drug intravenous delivery rate potency ratioand an effective bioavailability,defined as the ratio of intravenous-to-oral delivery rates of drug required to produce the same response. Using a combined phar-macokinetic-pharmacodynamic model, the impact of various factors on the effective bioavailability and on its estimation, using the intravenous-to-oral dose ratio required to produce the same area under the response time curve after acute administration, are explored. It is proposed that attention be centered more on comparison of rates of administration, or doses, that produce equal responses than on bioavailability per se.
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    Clinical applicability of current pharmacokinetic models: Splanchnic elimination of 5-fluorouracil in cancer patients (1988)
    Springer
    Journal of pharmacokinetics and pharmacodynamics 16 (1988), S. 229-249 
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    ISSN: 1573-8744
    Keywords: Michaelis-Menten kinetics ; sinusoidal perfusion model ; venous equilibration model ; distributed model ; convection-dispersion model ; organ heterogeneity ; bioavailability ; pooling of data ; kinetic parameter estimation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract What can be inferred from limited clinical data by using current models of hepatic elimination? We examined this question by analyzing previously published data on the steady-state uptake of the anticancer agent 5-fluorouracil (5-FU) in seven cancer patients in terms of the venous equilibration model, the undistributed and distributed forms of the sinusoidal perfusion model, and the convection-dispersion model. Because of appreciable extrasplanchnic removal of 5-FU, the value of the steady infusion rate was not used in our analysis. When the data from all patients were pooled by plotting the measured hepatic venous concentration against the measured hepatic arterial concentration, the high concentration data fell on a limiting straight line of slope 1, indicating that at high dose rates elimination of 5-FU in both the liver and gastrointestinal tract was close to saturation. The intercept of this line gave a model-independent estimate of Vmax/Q= 48.0±11.6 (SD) μM for the pooled data set, where Vmax is the maximum splanchnic elimination rate of 5-FU, and Q is the hepatic blood flow. The low concentration data points fell on a limiting straight line through the origin, from which model-dependent values of the Michaelis constant were determined. The venous equilibration model gave K m=9.4μM,while the undistributed sinusoidal perfusion model gave K m * =26,5μM. With these values of K m,both models fit the pooled data equally well. These methods were applied to analyses of the five individual data sets which contained sufficiently high concentration data points. The resulting mean values were Vmax/Q=41.0±5.1 (sem) μM,K m=8.4±1.3μM and K m * =23.2±3.2 μM. However, the splanchnic region is a highly heterogeneous organ system, for which an undistributed analysis provides no more than an upper bound on the Michaelis constant K m + (K m + ⩽K m * ).A perfusion model distributed to represent total splanchnic elimination is developed in the Appendix. Using previous estimates of the degree of functional heterogeneity in the liver alone, this model yields K m + values for individual patients which have a mean of 20.3±2.8 μM.
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    Prodrugs for Improved Oral β-Estradiol Bioavailability (1988)
    Springer
    Pharmaceutical research 5 (1988), S. 44-47 
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    ISSN: 1573-904X
    Keywords: estradiol ; prodrugs ; bioavailability ; first-pass metabolism
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Prodrugs of β-estradiol (1) were prepared with the objective of improving its oral bioavailability. β-Estradiol-3-acetylsalicylate (2), β-estradiol-3-salicylate (3), and β-estradiol-3-anthranilate (4) were synthesized. With these prodrugs the 3-phenolic hydroxy group of estradiol was protected, so that first-pass conjugative metabolism could be reduced. Prodrug hydrolysis rates in dog and human plasma in vitro were determined. Deacetylation of estradiol-3-acetylsalicylate was much more rapid than its hydrolysis to estradiol. In dogs, oral estradiol bioavailability after administration of 2 and 4 was 17-fold and 5-fold higher, respectively, than after oral 1.
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    Phosphorus bioavailability of fluvial sediments determined by algal assays (1988)
    Springer
    Hydrobiologia 160 (1988), S. 9-18 
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    ISSN: 1573-5117
    Keywords: bioassay ; phosphorus ; sediments ; bioavailability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Eroding bank soils and riverine suspended sediments from the Flathead River-Lake ecosystem, Montana, USA, were cultured with the alga Selenastrum capricornutum Printz in PAAP medium with the sediments as the sole source of phosphorus. Extraction of phosphorus by NaOH and nitrilotriacetic acid (NTA) solutions were compared to results from algal bioassays. The fine sediment particles transported into Flathead Lake during spring runoff had the highest availability (i.e. 6% of total phosphorus). Bank soils which contained the greatest percentage of fine clays exhibited similar (i.e. 4% of total phosphorus) availability. Bank soils containing predominantly organic phosphorus had the lowest availability. Spearman's rank correlation indicated significance at the 5% test level between algal assay estimates of available phosphorus and both chemical extraction techniques.
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    Bioavailability of different phosphorus forms in freshwater systems (1988)
    Springer
    Hydrobiologia 170 (1988), S. 133-155 
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    ISSN: 1573-5117
    Keywords: bioavailability ; phosphorus ; dissolved ; particulate ; bioassay ; 32P
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The recent literature on the bioavailability of different forms of P in freshwater systems is reviewed. Bioavailable P is defined as the sum of immediately available P and the P that can be transformed into an available form by naturally occurring processes. Methods used to estimate the bioavailable P pool, which vary between studies largely depending on the time perspective applied, are critically evaluated. Most studies on particulate P aim to determine the potentially available P pool. Potential bioavailability of particulate P is normally analysed in bioassays with algal yield determinations and the available P fraction is characterized from interpretations of results of sequential chemical extractions. NaOH-extractable P is in most studies the most algal-available P fraction. For soil samples and tributary water particulate matter, NaOH-P has often been found to be equal to algal extractable P. In other studies depletions of NaOH-P have accounted for the algal P uptake, but only a minor proportion of the fraction has been utilized. Organic P in lake water particulate matter and bed sediments of eutrophic lakes can also be algal-available to a significant extent. Studies on the bioavailability of dissolved P have often been concerned with immediate availability, or the minimum amount of available P. Such studies need other types of experimental design and normally assays with radiotracers are used. Immediately available P is frequently found to be less than P chemically assessed as dissolved reactive P (DRP) at low (〈 10 µg DRP·l-1) concentrations. However, immediate availability may also approach or exceed DRP concentrations, especially at higher concentrations. Potential bioavailability, assayed as for particulate P, may generally render higher bioavailability than P assayed as immediately available. Large fractions of dissolved P remain unutilized and are primarily found in the high molecular weight fraction of dissolved P.
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    Enhanced dissolution and oral bioavailability of α-tocopheryl esters by dimethyl-β-cyclodextrin complexation (1988)
    Springer
    Journal of inclusion phenomena and macrocyclic chemistry 6 (1988), S. 167-174 
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    ISSN: 1573-1111
    Keywords: α-Tocopheryl acetate ; α-tocopheryl nicotinate ; dimethyl-β-cyclodextrin ; inclusion complexation ; solubility ; dissolution rate ; bioavailability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Inclusion complexation of heptakis (2,6-di-O-methyl)-β-cyclodextrin (DM-β-CyD) with α-tocopheryl acetate and α-tocopheryl nicotinate in aqueous solution was studied by the solubility method. The aqueous solubilities of the esters were about 105 times increased by DM-β-CyD complexation. The phase-solubility diagram of the tocopheryl ester-DM-β-CyD systems showed a typicalA p type, and the stability constants (K) of high-order complexes were estimated by analyzing the upward curvature of the diagrams. The solid complex of α-tocopheryl nicotinate with DM-β-CyD in a molar ratio of 1∶2 was prepared by the kneading method. The dissolution rate of the solid complex was much greater than that of the drug itself, and the rapidly dissolving form of α-tocopheryl nicotinate, as an example, showed a markedly increased bioavailability (about 70-fold) after oral administration to fasted dogs.
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    Pharmacokinetics and Bioavailability of Hydromorphone: Effect of Various Routes of Administration (1988)
    Springer
    Pharmaceutical research 5 (1988), S. 718-721 
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    ISSN: 1573-904X
    Keywords: hydromorphone ; intranasal ; transdermal ; pharmacokinetics ; bioavailability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The pharmacokinetics and bioavailability of hydromorphone following various routes of administration, i.e., intravenous, oral, intranasal, and transdermal, were investigated in rabbits. Hydromorphone plasma concentrations were determined by reverse-phase high-performance liquid chromatography (HLPC). Comparison of area under the concentration versus time curve (AUC) between intravenous and oral administrations showed a low bioavailability of hydromorphone after oral administration. The nasal absorption of hydromorphone was studied by the in situ nasal recirculation technique, and the results showed that hydromorphone is well absorbed from the nasal mucosa. The transdermal permeation of hydromorphone was also evaluated for 24 hr and a steady-state plasma concentration (0.135 µg/ml) was achieved during the 6- to 24-hr periods following the application of a transdermal patch on the inner pinna of the rabbit's ear.
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    Naltrexone-3-salicylate (a Prodrug of Naltrexone): Synthesis and Pharmacokinetics in Dogs (1988)
    Springer
    Pharmaceutical research 5 (1988), S. 113-115 
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    ISSN: 1573-904X
    Keywords: naltrexone ; prodrug ; naltrexone salicylate ; bioavailability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Naltrexone-3-salicylate (3), a prodrug of naltrexone (1), was prepared by a simple procedure from naltrexone-3-acetylsalicylate (2). The plasma (dog and human) hydrolysis half-life of 3 was found to be approximately 30 min. Compound 2 was previously shown to hydrolyze in dog and human plasma with a fast deacetylation step to 3, followed by slower hydrolysis of 3 to 1 (t 1/2, ∼30 min). Oral naltrexone bioavailability was greatly improved (∼30-fold) after oral administration of 3 to dogs, similar to the improvement observed after oral administration of 2. The half-life of naltrexone in dogs after oral administration of 3 was similar to that observed after oral administration of 2 (∼1 hr).
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    Saturable Binding of Cyclosporin A to Erythrocytes: Estimation of Binding Parameters in Renal Transplant Patients and Implications for Bioavailability Assessment (1988)
    Springer
    Pharmaceutical research 5 (1988), S. 80-85 
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    ISSN: 1573-904X
    Keywords: cyclosporin ; saturable binding ; erythrocyte ; bioavailability ; therapeutic drug monitoring
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Cyclosporin (CyA) exhibits saturable binding to erythrocytes. A one-site binding model was fitted to data from renal transplant patients receiving CyA therapy. The average maximum binding capacity is 2560 µg CyA/liter of packed erythrocytes; the unbound CyA concentration associated with 50% saturation of the binding site is 67 µg/liter. Analysis indicates that whole-blood CyA measurement to monitor drug therapy should be viewed cautiously, particularly when the hematocrit varies considerably. The error in estimating absolute bioavailability at steady state from whole-blood measurements, resulting as a consequence of the saturable binding, has been explored. Although extrapolation to the therapeutic situation, which involves transient drug administration, is difficult, errors of up to 25% are anticipated. When an accurate estimate of bioavailability is required, analysis based on plasma data is proposed. For bioequivalence testing, both blood and plasma CyA data are equally acceptable.
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    Bioavailability of dalargin and its metabolism when administered intranasally to rats (1988)
    Springer
    Bulletin of experimental biology and medicine 106 (1988), S. 968-970 
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    ISSN: 1573-8221
    Keywords: dalargin ; opioids ; metabolism ; bioavailability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
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    URL: http://dx.doi.org/10.1007/BF00834651
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    Pharmacokinetics and absolute bioavailability of salbutamol in healthy adult volunteers (1987)
    Springer
    European journal of clinical pharmacology 32 (1987), S. 631-634 
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    ISSN: 1432-1041
    Keywords: salbutamol ; albuterol ; pharmacokinetics ; bioavailability ; healthy volunteers
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Salbutamol was administered to sixteen healthy male volunteers intravenously and by mouth in liquid, tablet, and capsule form using a Latin-Squares design. Pharmacokinetic parameters from intravenous data were similar to previously reported values obtained with oral administration, with a mean terminal half-life of 3.8 h and a mean clearance of 439 ml·min−1·1.73 m−2. Peak plasma concentrations of 10–20 ng·ml−1 were obtained 1–3 h following oral administration. The absolute bioavailability of each of the oral preparations was 44%. While statistically significant differences in lag time and time to peak concentration were noted among the various oral preparations, the drug is rapidly absorbed in all three dosage forms and the observed differences are unlikely to be of clinical significance.
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    Bioavailability of disopyramide in normal volunteers using unbound concentration (1987)
    Springer
    European journal of clinical pharmacology 32 (1987), S. 625-629 
    Details
    ISSN: 1432-1041
    Keywords: disopyramide ; bioavailability ; saturable binding ; pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The pharmacokinetics of disopyramide were determined in 10 healthy volunteers after a 300 mg oral dose and again after a 2mg/kg i.v. dose. The unbound clearance was 599 ml/min and the unbound renal clearance 310 ml/min. The terminal elimination rate constant of unbound drug was 0.180 h−1 after the i.v. dose and 0.203 h−1 after the oral dose. The absorption rate constant was 0.53−1 and the maximum peak concentration occurred after 3.2 h. The bioavailability was 0.809 using the area under the unbound plasma concentration time curve. Although a saturable plasma protein binding was found in all subjects the bioavailability using the total concentration, in contrast to theoretical expectations, showed the same value (0.813) as the unbound concentrations.
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    Pharmacokinetics of meptazinol after parenteral administration in the elderly (1987)
    Springer
    European journal of clinical pharmacology 31 (1987), S. 733-736 
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    ISSN: 1432-1041
    Keywords: meptazinol ; pharmacokinetics ; elderly patients ; healthy volunteers ; bioavailability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary We have determined the pharmacokinetics of meptazinol after its intravenous and intramuscular administration in a crossover study in 7 elderly hospital in-patients (〉70 years), and have compared with the results from 14 healthy, young volunteers (ages 20–40 years). The systemic availability after i.m. administration was comparable to that after i.v. administration, a result consistent with the physicochemical properties of the drug. There was a slight, but statistically significant (p〈0.01) prolongation in t1/2z in the elderly (mean 2.93 h) compared with the young (mean 2.06 h). This was associated with a 25% lower clearance in the elderly rather than with any alteration in volume of distribution. However, these changes would not appear to be substantial enough to require a revised dosage recommendation for meptazinol for this age group.
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    Bioavailability of indomethacin from a modified release system containing indomethacin as the lysine salt (1987)
    Springer
    European journal of clinical pharmacology 32 (1987), S. 85-87 
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    ISSN: 1432-1041
    Keywords: indomethacin ; lysine salt ; controlled release formulation ; plasma concentration ; bioavailability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The bioavailability of a new controlled release formulation of indomethacin lysine salt in tablets was tested in 6 healthy humans against a conventional indomethacin lysinate formulation in capsules. Both contained 100 mg of the drug, i.e. 70 mg indomethacin. Peak plasma levels were lower and more lasting and the AUC was higher with the new controlled release formulation. The latter on average produced active plasma levels for 12 h, and so it can be recommended for twice daily administration.
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    Pharmacokinetics of free and total flucloxacilin in newborn infants (1987)
    Springer
    European journal of clinical pharmacology 32 (1987), S. 403-409 
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    ISSN: 1432-1041
    Keywords: flucloxacillin ; newborn infants ; bioavailability ; plasma protein binding ; side-effects
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Flucloxacillin 50 mg/kg b.w. was administered intravenously (in combination with ampicillin/gentamicin) and orally (with amoxicillin) to 9 newborn infants (gestational age 33–41 weeks) to treat bacterial infections. The concentrations of flucloxaxillin in plasma and urine after i.v. injection were analysed according to an open two-compartment model, and the plasma protein binding of flucloxacillin and its distribution to blood cells and plasma water in whole blood were determined. Considerable differences were found from values reported in adults. The terminal half-life averaged 4 h 38 min and was significantly correlated with gestational age. Plasma clearance was low (0.744 ml·min−1·kg−1), due to the small renal clearance (0.182 ml·min−1·kg−1), whilst non-renal clearance (0.563 ml·min−1·kg−1) was approximately the same as in adults. The mean apparent volume of distribution of total drug (Vz) was 0.280 l/kg. The corresponding volume of distribution of unbound drug (V 1 u + V 2 u ) was 1.74 l/kg, which indicates considerable extravascular drug binding. The plasma protein binding of flucloxacillin (mean 86.3%) was significantly correlated with gestational age and the bilirubin/albumin concentration ratio. Bioavailability after oral administration, when corrected for changes in terminal half-life, was 47.7%, which is only slightly lower than that reported in adults. Since the plasma concentrations after both i.v. and oral administration were well above the MIC-values generally reported for Staphylococcus aureus, and since few side-effects were observed, intravenous injection or, in selected cases, oral administration of flucloxacillin appears to be a reliable therapy for the treatment of infections due to sensitive strains of S. aureus in premature newborn infants.
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    Food and guar decrease absorption of trimethoprim (1987)
    Springer
    European journal of clinical pharmacology 32 (1987), S. 427-429 
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    ISSN: 1432-1041
    Keywords: trimethoprim ; food effect ; guar effect ; bioavailability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Absorption of trimethoprim suspension 3 mg/kg has been studied in 12 healthy adult volunteers when given alone, with food or with food and guar, using a randomised Latin-squares study design. Serum and urine trimethoprim concentrations were followed for 24 h. The mean peak serum concentration was higher when fasting subjects were treated (mean: 2.35, 1.84 and 1.97 µg/ml for the fasting, food and food + guar groups, respectively; ANOVA p〈0.001 for the difference between fasting and non-fasting values). The times of the peak serum concentrations did not differ. Food ingestion decreased the area under the curve by 22.2%, as did food + guar. For maximal efficacy trimethoprim should be administered between meals.
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    Pharmacokinetics and systemic availability of the antihypertensive agent indoramin and its metabolite 6-hydroxyindoramin in healthy subjects (1987)
    Springer
    European journal of clinical pharmacology 32 (1987), S. 619-623 
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    ISSN: 1432-1041
    Keywords: indoramin ; 6-hydroxyindoramin ; bioavailability ; pharmacokinetics ; healthy volunteers
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary We have studied the pharmacokinetics and absolute systemic availability of indoramin (50 mg) given orally in solution or as a tablet with reference to intravenously administered drug (0.15 mg/kg) in 9 healthy volunteers. After intravenous administration the median apparent volume of distribution was 6.3l·kg−1, plasma clearance was 20.0 ml·min−1·kg−1, and terminal half-time was 4.1 h. When given by tablet indoramin was absorbed with moderate rapidity, with a median tmax of 1.5 h. The median systemic availability was 24%. After oral administration in solution the drug was more rapidly absorbed, with a median tmax of 1.0 h (p〈0.01). The median systemic availability was 43% (15–85%). Plasma concentrations of an active metabolite, 6-hydroxyindoramin, after single oral doses in either dosage form, were of a similar order to those of unchanged drug and fell with similar rapidity. After intravenous administration, however, concentrations of the metabolite were negligible.
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    Pharmacokinetics and bioavailability of carvedilol, a vasodilating beta-blocker (1987)
    Springer
    European journal of clinical pharmacology 33 (1987), S. 511-513 
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    ISSN: 1432-1041
    Keywords: carvedilol ; BM 14.190 ; pharmacokinetics ; bioavailability ; dose-linear kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The pharmacokinetics and absolute bioavailability of carvedilol have been studied in 20 male healthy volunteers in a randomised 4-period, cross-over trial. Carvedilol 12,5 mg was given i.v., 50 mg was administered p.o. as a suspension and 25 and 50 mg were given in a capsule formulation. For the 50 mg capsule Cmax was 66 µg·l−1, tmax 1.2 h, t1/2 6.4 h. The t1/2 after i.v. administration was 2.4 h, CL 589 ml/min and Vz 132 l. The absolute bioavailability was 24% (50 mg capsule). The kinetics after the 25 and 50 mg capsules were consistent with dose linearity.
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    Effect of aluminum phosphate on the bioavailability of ranitidine (1987)
    Springer
    European journal of clinical pharmacology 32 (1987), S. 97-99 
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    ISSN: 1432-1041
    Keywords: ranitidine ; aluminium phosphate ; antacids ; bioavailability ; drug interaction ; healthy volunteers
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The effect of aluminum phosphate on the bioavailability of ranitidine has been investigated in 10 young, healthy volunteers. Following a random cross over design, each subject took at a 1 week interval 150 mg ranitidine alone or with 11 g aluminum phosphate. Plasma and urine ranitidine levels were measured by HPLC. The antacid reduced both the maximum plasma ranitidine concentration by 40% and the area under the curve by 30%. Elimination of ranitidine was not changed. The results indicate that aluminum phosphate significantly diminished the bioavailability of ranitidine.
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    Concurrent intravenous administration of a labeled tracer to determine the oral bioavailability of a drug exhibiting Michaelis-Menten metabolism (1987)
    Springer
    Journal of pharmacokinetics and pharmacodynamics 15 (1987), S. 615-631 
    Details
    ISSN: 1573-8744
    Keywords: bioavailability ; error in bioavailability estimation ; Michaelis-Menten ; concurrent intravenous and oral dosing ; labeled intravenous tracer dose ; instantaneous clearance ; computer simulation ; venous equilibration model
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The theoretical accuracy of concurrent administration of labeled intravenous tracer and oral doses to estimate the bioavailability of drugs exhibiting Michaelis-Menten kinetics was determined by computer simulation. The simulation model consisted of sampling and hepatic compartments with elimination occurring by hepatic metabolism according to the venous equilibration model. The relationships between error in bioavailability estimation and dose, metabolic activity (Vmax),first-order absorption rate constant (k a), and volume of distribution (V) and the fraction of the dose absorbed were examined. Error was hypothesized to be relatively low when conditions result in a relatively constant value of clearance after oral dosing or when the concentration-time curves after intravenous and oral dosing are similar. The results were consistent with these hypotheses and, under most conditions, error was less than 15%. The effects, on error, of altering the intravenous tracer dose input and having a lag time in absorption of drug from the oral dose were also determined. In general, accuracy was improved by delaying administration of the iv tracer for a time equal to 50% of the oral dose peak time or by administering the tracer dose by constant-rate infusion from the time of oral dosing to the peak time. Lag time in absorption of the oral dose was shown to often result in overestimates in bioavailability of greater than 50%.
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    A comparison of the Two One-Sided Tests Procedure and the Power Approach for assessing the equivalence of average bioavailability (1987)
    Springer
    Journal of pharmacokinetics and pharmacodynamics 15 (1987), S. 657-680 
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    ISSN: 1573-8744
    Keywords: bioavailability ; bioequivalence ; hypothesis testing ; interval hypotheses
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The statistical test of the hypothesis of no difference between the average bioavailabilities of two drug formulations, usually supplemented by an assessment of what the power of the statistical test would have been if the true averages had been inequivalent, continues to be used in the statistical analysis of bioavailability/bioequivalence studies. In the present article, this Power Approach (which in practice usually consists of testing the hypothesis of no difference at level 0.05 and requiring an estimated power of 0.80) is compared to another statistical approach, the Two One-Sided Tests Procedure, which leads to the same conclusion as the approach proposed by Westlake (2) based on the usual (shortest) 1–2α confidence interval for the true average difference. It is found that for the specific choice of α=0.05 as the nominal level of the one-sided tests, the two one-sided tests procedure has uniformly superior properties to the power approach in most cases. The only cases where the power approach has superior properties when the true averages are equivalent correspond to cases where the chance of concluding equivalence with the power approach when the true averages are notequivalent exceeds 0.05. With appropriate choice of the nominal level of significance of the one-sided tests, the two one-sided tests procedure always has uniformly superior properties to the power approach. The two one-sided tests procedure is compared to the procedure proposed by Hauck and Anderson (1).
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    In Vitro and In Vivo Interactions of Furosemide and Sucralfate (1987)
    Springer
    Pharmaceutical research 4 (1987), S. 171-172 
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    ISSN: 1573-904X
    Keywords: furosemide ; sucralfate ; adsorption ; bioavailability ; diuretic effect
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
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    URL: http://dx.doi.org/10.1023/A:1016487507420
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    Between-Lot and Within-Lot Comparisons of Bioavailability of Macrocrystalline Nitrofurantoin Capsules (1987)
    Springer
    Pharmaceutical research 4 (1987), S. 499-503 
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    ISSN: 1573-904X
    Keywords: nitrofurantoin macrocrystals ; bioavailability ; urinary excretion ; drug absorption
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Comparative bioavailability studies should be designed and the resulting data evaluated based on estimates of both intersubject and intrasubject variances in the kinetic parameters for the particular drug products(s) being studied. This report presents the results of two comparative bioavailability studies. In the first study, three production lots of macrocrystalline nitrofurantoin capsules (Macrodantin) were compared in 21 subjects, and in the second study, capsules from one production lot were administered to 21 different subjects on three occasions. Both model-independent kinetic parameters for urinary excretion and a one-compartment model with zero-order absorption were used to evaluate both the rate and the extent of bioavailability. Overall the results showed a very low variance between and within production lots and a relatively large intersubject variance in the rate and extent of absorption.
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    An Equation for the Systemic Availability of Drugs Undergoing Simultaneous Enterohepatic Cycling, First-Pass Metabolism, and Intestinal Elimination (1987)
    Springer
    Pharmaceutical research 4 (1987), S. 195-199 
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    ISSN: 1573-904X
    Keywords: enterohepatic recirculation ; pharmacokinetics ; bioavailability ; area under the curve ; bile ; hepatic extraction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A relationship between systemic availability and its determinants has been derived for a physiologically realistic model of drug disposition that includes enterohepatic cycling (EHC), gallbladder emptying (with an arbitrary time course), first-pass metabolism to noncycling metabolites, and fecal excretion. Systemic availability (F) has been shown to be determined by the fraction of the dose initially absorbed (f a*), the fraction of the drug excreted into the GI tract that is reabsorbed with each cycle (f a), the hepatic extraction ratio (E), and the fraction of extracted drug that is transported to the gallbladder for EHC (f g) according to the relationship F = f a*(1 −E/(1 − f a f g E) The implications of the above relationship are that (1) systemic availability is dependent on EHC, (2) values of F calculated to be greater than unity cannot be explained simply by the presence of EHC, (3) calculations of E based on the usual expression F = f a* (1 − E) are erroneous for drugs subject to EHC, and (4) a compound that has a high systemic availability and is subject to EHC is not necessarily inefficiently metabolized. The quantitative interrelationship of systemic availability and its determinants is illustrated using a contour plot. Slices through the surface are used to demonstrate that the presence of EHC changes the sensitivity of F to changes in E.
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    Pharmacokinetics of Gold Sodium Thiomalate in Rabbits (1987)
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    Pharmaceutical research 4 (1987), S. 332-336 
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    ISSN: 1573-904X
    Keywords: pharmacokinetics ; gold ; rabbits ; intramuscular ; intravenous ; bioavailability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Male, New Zealand white rabbits (3.5–4.3 kg) received a single 2-mg/kg dose of gold sodium thiomalate (Myochrysine) via intramuscular (N = 4) and intravenous (N = 3) routes. Blood samples were drawn from the marginal ear vein for a period of 5–10 days. The concentration of gold in whole blood was determined using graphite furnace atomic absorption spectrophotometry. The blood concentration–time profiles obtained following both routes of administration were best described by a two-compartment open model with first-order absorption for the intramuscular route. Gold was absorbed rapidly with a mean (harmonic) absorption half-life of 9.0 min, with a peak concentration of 6.0 ± 1.0 µg/ml (N = 4). Blood concentrations declined in a biphasic manner; the mean α half-lives were 0.738 and 1.78 hr for the iv and im routes, respectively. The corresponding terminal (β) half-lives were 54.1 and 63.0 hr. The estimated volume of the central compartment (70 to 93 ml/kg) agreed closely with the rabbit blood volume. The mean ( ±SD) extent of the dose absorbed following intramuscular injection was 68.9 ± 12.4%.
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    Bioavailability and Pharmacokinetics of a New Sustained-Release Potassium Chloride Tablet (1987)
    Springer
    Pharmaceutical research 4 (1987), S. 409-411 
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    ISSN: 1573-904X
    Keywords: potassium chloride ; sustained-release tablet ; bioavailability ; pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The bioavailability of a new sustained-release potassium chloride (KC1) tablet, designed for once-a-day dosing, was compared to a KC1 elixir using urinary excretion data. The study utilized 25 male volunteers dosed in a crossover design in a dietary/activity-controlled environment. The regimens consisted of a total of 80 mEq of potassium in three equally divided doses of elixir every 6 hr and a single 80-mEq dose using four 20-mEq sustained-release (SR) tablets. The mean time to maximum rate of potassium urinary excretion was 2.2 hr for the first elixir dose and 5.5 hr after the SR tablet (P 〈 0.01), thereby supporting the prolonged-release properties of this formulation. After correction for baseline urinary potassium excretion, the mean total 24-hr urinary potassium excretion was 42.18 mEq for the elixir and 40.41 mEq for the SR tablet. The results indicate that the absorption pattern from the SR tablet is equal to three doses of KC1 elixir dosed 6 hr apart.
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    Correlation of Ibuprofen Bioavailability with Gastrointestinal Transit by Scintigraphic Monitoring of 171Er-Labeled Sustained-Release Tablets (1987)
    Springer
    Pharmaceutical research 4 (1987), S. 486-489 
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    ISSN: 1573-904X
    Keywords: scintigraphy ; neutron activation ; bioavailability ; ibuprofen ; sustained release ; gastrointestinal transit
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract External gamma scintigraphy was used to monitor the gastrointestinal (GI) transit of radiolabeled sustained-release tablets containing 800 mg ibuprofen in eight fasted healthy volunteers. Ibuprofen serum concentrations were determined from blood samples drawn sequentially over a 24-hr period. Serum concentrations and related parameters were correlated to the position of the dosage form in the GI tract from the scintiphotos. The sustained-release tablets were radiolabeled intact utilizing a neutron activation procedure, by incorporating 0.18% of 170Er2O3 (enriched to 〉96% 170Er) into the bulk formulation. After manufacture of the final dosage forms, the tablets were irradiated in a neutron flux (4.4 × 1013 n/cm2 · sec) for 2 min, converting the stable 170Er to radioactive 171Er (t 1/2 = 7.5 hr). Each tablet contained 50 µCi of 171Er at the time of administration. The scintigraphy studies suggested that the greatest proportion of ibuprofen was absorbed from this dosage form while the tablet was in the large bowel. The dosage forms eroded slowly in the small bowel and appeared to lose their integrity in the large bowel. In vitro studies showed only minimal effects of the neutron irradiation procedure on the dosage form performance.
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    Reduced bioavailability and effect of furosemide given with food (1986)
    Springer
    European journal of clinical pharmacology 29 (1986), S. 725-727 
    Details
    ISSN: 1432-1041
    Keywords: furosemide ; meal effect ; bioavailability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary 10 healthy volunteers were given 40 mg furosemide p. o. with and without breakfast. The meal reduced the peak level of furosemide and decreased its bioavailability by approximately 30%. A heavy meal given to 5 of the subjects had no further effect. The reduced bioavailability caused a reduction in the diuretic effect.
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    Treatment of liver disease with malotilate. A pharmacokinetic and pharmacodynamic phase II study in cirrhosis (1986)
    Springer
    European journal of clinical pharmacology 30 (1986), S. 407-416 
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    ISSN: 1432-1041
    Keywords: malotilate ; cirrhosis ; bioavailability ; liver fibrosis ; metabolite kinetics ; pharmacokinetics ; portal-systemic shunting ; urinary metabolites
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Malotilate, a sulphur-containing compound with antifibrotic and hepatoprotective properties in several animal models, has been investigated in cirrhotic patients. Nine patients with cirrhosis of various aetiologies and severity, and 4 healthy volunteers, participated in a pharmacokinetic study. After a single dose of 500 mg malotilate p.o. peak malotilate plasma concentration measured by GC-MS was 35 times higher in patients (median 0.70 µg/ml) than in controls (median 0.019 µg/ml). The median apparent oral clearance was approximately 50 times lower in cirrhotics (median 2.2l/min) than in healthy volunteers (118l/min). The apparent oral clearance was significantly correlated with indicators of portalsystemic shunting, such as the 2-h postprandial serum bile acids and the bioavailability of oral nitroglycerine. Urinary output of the glucuronidated metabolite-(M3), measured by HPLC, was normal in patients, whereas recovery of metabolite-M6 (resulting from ring opening and loss of sulphur) was reduced. Six patients in an open 6-month trial received malotilate 200 mg t.i.d. for 2 months and 400 mg t.i.d. for 4 months. The thrombocyte count increased and serum ferritin level fell in all patients, and serum cholinesterase rose and IgA decreased in 5 of 6. The other indicators of liver function did not show a significant change. Dry skin was the only possible adverse effect. It is concluded that first-pass elimination of malotilate is dramatically reduced in cirrhotics, and that a smaller amount of the drug reaches the liver in such patients. Malotilate was well tolerated, even in patients with advanced disease.
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    Correlations between in vitro dissolution, in vivo bioavailability and hypoglycaemic effect of oral glibenclamide (1986)
    Springer
    European journal of clinical pharmacology 31 (1986), S. 177-182 
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    ISSN: 1432-1041
    Keywords: glibenclamide ; bioavailability ; pharmacokinetics ; dissolution ; hypoglycaemia ; healthy volunteers
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary A study has been carried out investigating four different marketed oral preparations of glibenclamide, correlating the effectiveness of the drug in these preparations in lowering plasma glucose concentrations with (i) the in vitro dissolution of the drug, measured by the British Pharmacopoeal and Desaga methods, and (ii) the in vivo bioavailability, assessed in 12 healthy human volunteers. The two dissolution methods yielded different rank orders of ease of dissolution of the drug from the various preparations; the findings of neither dissolution method correlated adequately with the results of the in vivo bioavailability studies, which correctly predicted the abilities of the preparations to reduce plasma glucose concentrations. Relative to an oral glibenclamide solution the bioavailabilities of the drug from three tablet preparations were 0.69, 0.49 and 0.24. The mean elimination half-life of the drug was 1.5 h and assuming complete bioavailability of the drug from oral solution the mean systemic clearance was 0.095 l kg−1h−1, and the mean apparent volume of distribution was 0.20 l kg−1. It is concluded that it may be unsafe to use in vitro dissolution data as a basis for assessing the bioequivalences of different glibenclamide preparations intended for oral use.
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    URL: http://dx.doi.org/10.1007/BF00606655
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    Effect of food on cibenzoline bioavailability (1986)
    Springer
    European journal of clinical pharmacology 30 (1986), S. 367-369 
    Details
    ISSN: 1432-1041
    Keywords: cibenzoline ; bioavailability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Eighteen healthy adult volunteers received 160 mg oral capsule doses of cibenzoline in an open-label, four-way randomized crossover study designed to determine the influence of food on cibenzoline pharmacokinetics. Cibenzoline was administered 1 h prior to, with, and 1 h following a standard breakfast as well as under fasting conditions. There was no change in any bioavailability parameter when the data following drug ingestion 1 h prior to food were compared to the fasted state. Bioavailability parameters obtained when drug was taken during the meal or 1 h after the meal suggested that the rate of absorption was slightly decreased in the presence of food, while the extent of absorption was unaltered. The decreased absorption rate in the presence of food is not expected to be of clinical significance. The presence of food is not expected to affect the bioavailability of cibenzoline to the extent of clinical significance.
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    URL: http://dx.doi.org/10.1007/BF00541547
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    Effect of sucralfate on the bioavailability of cimetidine (1986)
    Springer
    European journal of clinical pharmacology 30 (1986), S. 493-494 
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    ISSN: 1432-1041
    Keywords: cimetidine ; sucralfate ; bioavailability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Twelve, healthy fasting, subjects received 200 mg cimetidine orally either with water or 1 g sucralfate in a randomized, single dose, two-way crossover study. Blood samples were taken for 12 h and urine was collected for 24 h. Cimetidine in plasma and urine was analysed by HPLC. There was no significant difference between the two treatments in peak plasma concentration, time to peak plasma concentration, area under the plasma concentration-time curve and urinary excretion. The results indicate that sucralfate did not reduce the bioavailability of cimetidine.
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    Oral bioavailability of high-dose metoclopramide (1986)
    Springer
    European journal of clinical pharmacology 31 (1986), S. 41-44 
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    ISSN: 1432-1041
    Keywords: metoclopramide ; high-dose ; bioavailability ; adverse effects
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The oral bioavailability of high-dose metoclopramide was studied in 12 patients, who received oral or intravenous (i.v.) metoclopramide in random order with each of 2 consecutive courses of cytotoxic chemotherapy. The terminal half-life of metoclopramide was 7.1±0.4 h (mean±SEM) and was not affected by the route of drug administration. Mean bioavailability was 86.6±4.7% and the range (65–118%) was less than that reported for standard doses. Neither half-life nor bioavailability was significantly correlated with age. Adverse effects were mild and were similar for both oral and iv metoclopramide. Oral high-dose metoclopramide, given in the same doses as for i.v. administration, should therefore be as effective as the i.v. regimen and may be easier to administer.
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    URL: http://dx.doi.org/10.1007/BF00870983
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    Pharmacokinetics of piroximone (MDL 19.205) in healthy volunteers (1986)
    Springer
    European journal of clinical pharmacology 31 (1986), S. 239-242 
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    ISSN: 1432-1041
    Keywords: piroximone ; cardiotonic drug ; pharmacokinetics ; bioavailability ; healthy volunteers
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Six healthy, male subjects received single intravenous and oral doses of piroximone. Plasma piroximone concentrations were assayed up to 8 h after each dose by HPLC. Urinary excretion of the parent compound was also determined. Following the oral dose, piroximone reached peak plasma concentrations within 30 to 90 min. The t1/2 of the terminal decay phase was 2.8 h, the mean apparent volume of distribution was 2.5 l/kg, and the mean total body clearance was 755 ml/min. Mean urinary recovery of parent drug within 24 h was 50% after the intravenous dose and 41% after the oral dose. Renal clearance accounted for approximately 50% of total body clearance. Oral bioavailability, estimated from AUC or urinary recovery, was 80%.
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    Pharmacokinetics of N-acetylcysteine in man (1986)
    Springer
    European journal of clinical pharmacology 31 (1986), S. 217-222 
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    ISSN: 1432-1041
    Keywords: N-acetylcysteine ; bioavailability ; slow-release formulation ; pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary N-Acetylcysteine was given intravenously and as three fast dissolving and one slow-release formulation, on separate occasions, as a single dose of 600 mg to 10 fasting (5 men and 5 women) healthy volunteers. Blood and urine were sampled for the following 12 h. Renal clearance constituted around 30% of total body clearance, which was 0.21 l/h/kg. Volume of distribution was 0.33 l/kg, consistent with distribution mainly to extracellular water. The late elimination half-life was 2.27 h and the mean residence time 1.62 h. The slow-release tablet resulted in a flattened plasma concentration-time curve typical of slow release formulations, while the other three oral formulations were rapidly absorbed. The oral availability of N-acetylcysteine varied between 6 and 10%, with the slow-release tablet having the lowest and the fast dissolving tablet the highest availability.
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    URL: http://dx.doi.org/10.1007/BF00606662
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    Pharmacokinetics of ketanserin and its metabolite ketanserin-ol in man after intravenous, intramuscular and oral administration (1986)
    Springer
    European journal of clinical pharmacology 31 (1986), S. 343-350 
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    ISSN: 1432-1041
    Keywords: ketanserin ; serotonin antagonist ; antihypertensive drug ; pharmacokinetics ; bioavailability ; dose-proportionality ; metabolite kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The pharmacokinetics of ketanserin (R 41468), a novel serotonin S2-receptor blocking agent widely investigated for its effect on acute and chronic hypertension, has been studied in 10 healthy male subjects. They received single 10 mg doses i.v. and i.m., and 20, 40 and 60 mg solutions of ketanserin by mouth, in a five-way cross-over design. The model-independent kinetics of i.v. ketanserin were characterized by a terminal half-life of 14.3±4.4 h, a moderate plasma clearance (CL=565±57 ml/min) and a large tissue distribution (Vss=268±71 l, Vz=703±204 l; mean ± SD). Following i.m. administration, peak levels of nearly 200 ng/ml were attained within 10 minutes and the absolute bioavailability was 112±23%. After oral dosing, peak levels of ketanserin were reached within 1 h. The peak level and AUC increased in proportion to the dose. The absolute bioavailability was 46.8, 50.4 and 55.5% for 20, 40 and 60 mg doses and they conformed to the predicted bioavailability based on i.v. clearance data. The terminal half-life of 17 h and the urinary excretion of parent drug (about 0.7% of the dose) were similar after oral and parenteral dosing. The kinetics of ketanserin-ol, the major metabolite of ketanserin formed by ketone reduction, was also studied. Because of its negligible pharmacological activity, the contribution of ketanserin-ol to the overall therapeutic effect of ketanserin is small, in spite of its 1.6-times (parenteral) to 3.2-times (oral) higher plasma level than that of ketanserin. The particular role of the metabolite is discussed in the light of the clinical pharmacokinetics of ketanserin.
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    URL: http://dx.doi.org/10.1007/BF00981135
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    Comparative bioavailability and pharmacokinetics of noscapine hydrogen embonate and noscapine hydrochloride (1986)
    Springer
    European journal of clinical pharmacology 31 (1986), S. 367-369 
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    ISSN: 1432-1041
    Keywords: noscapine hydrochloride ; noscapine hydrogen embonate ; pharmacokinetics ; bioavailability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The relative bioavailability and pharmacokinetics of two orally administered aqueous suspensions of noscapine hydrogen embonate were compared with those of noscapine hydrochloride solution. Noscapine hydrochloride showed faster absorption and gave a higher peak concentration than the embonate. The average bioavailability of the embonates was 71% of that of the noscapine solution (p〈0.05). No significant difference was observed when the embonate was administered with water, polyvidone and flavouring agents.
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    URL: http://dx.doi.org/10.1007/BF00981140
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    Influence of physical exercise on the pharmacokinetics of propranolol (1986)
    Springer
    European journal of clinical pharmacology 31 (1986), S. 375-377 
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    ISSN: 1432-1041
    Keywords: propranolol ; pharmacokinetics ; exercise ; indocyanine green clearance ; bioavailability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The pharmacokinetics of propranolol after oral and intravenous administration was studied at rest and on an exercise day in 8 healthy subjects. On the exercise day the subjects performed physical exercise for 7 h, consisting of bicycle ergometer exercise at 50% of maximal work capacity and outdoor walking. Propranolol (80 mg p.o., or 0.2 mg/kg body weight i.v.) was administered 30 min before the start of the exercise. After oral administration the terminal phase halflife, (t1/2β) and area under the curve (AUC) were both significantly reduced on the exercise day compared to the rest day. The bioavailability of propranolol was reduced by prolonged physical exercise and plasma levels of propranolol were about 30% lower at the end of the exercise day than at the end of the rest day. After intravenous administration, t1/2β was also reduced on the exercise day as compared to the rest day. AUC, clearance and volume of distribution did not differ on the two days. On the other hand, indocyanine green (ICG) clearance was significantly reduced during the bicycle ergometry periods on the exercise day. The combination of reduced ICG clearance, suggesting a reduction in hepatic blood flow, and a decreased t1/2β and unchanged clearance of propranolol on the exercise day was unexpected.
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    URL: http://dx.doi.org/10.1007/BF00981142
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    The pharmacokinetics of tetrabenazine and its hydroxy metabolite in patients treated for involuntary movement disorders (1986)
    Springer
    European journal of clinical pharmacology 29 (1986), S. 703-708 
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    ISSN: 1432-1041
    Keywords: tetrabenazine ; hydroxytetrabenazine ; pharmacokinetics ; bioavailability ; active metabolite ; movement disorder
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The pharmacokinetics of tetrabenazine and a metabolite, hydroxytetrabenazine, have been investigated in seven patients being treated for involuntary movement disorders. Tetrabenazine had a very low oral systemic availability (mean 0.049±0.032 SD). First-pass metabolism to hydroxytetrabenazine was extensive, and the systemic availability for this metabolite was high (mean 0.81±0.30 SD). Since hydroxytetrabenazine has been reported to be as active as tetrabenazine in depleting brain amines, and is present at much higher plasma concentrations than the parent drug, it is likely that this metabolite is the more important therapeutic moiety.
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    URL: http://dx.doi.org/10.1007/BF00615962
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    Comparative kinetics of phenobarbital after administration of the acid and the propylhexedrine salt (barbexaclone) (1986)
    Springer
    European journal of clinical pharmacology 29 (1986), S. 729-730 
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    ISSN: 1432-1041
    Keywords: phenobarbital ; propylhexedrine salt ; barbexaclone ; bioavailability ; pharmacokinetics ; healthy volunteers
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The kinetics of phenobarbital (PB) was compared after oral administration of equivalent doses of the drug as the acid or the propylhexedrine salt (barbexaclone) to 7 normal volunteers. The absorption and elimination parameters were very similar. It was concluded that propylhexedrine did not affect the serum kinetics of PB given as barbexaclone.
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    Pharmacokinetics of dezocine, a new analgesic: Effect of dose and route of administration (1986)
    Springer
    European journal of clinical pharmacology 30 (1986), S. 121-123 
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    ISSN: 1432-1041
    Keywords: dezocine ; opioid analgesics ; pharmacokinetics ; healthy volunteers ; bioavailability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The pharmacokinetics of intravenous (IV) dezocine, and bioavailability of intramuscular (IM) and subcutaneous (SQ) dezocine, were evaluated in healthy male volunteers. Elimination half-life following 5, 10, and 20 mg IV doses averaged 2.6–2.8 h, and was independent of dose. Clearance decreased slightly, although significantly, with dose. After Deltoid IM injection, dezocine was rapidly absorbed (peak level: 0.6 h after dose), with bioavailability 97%. Thus dezocine has extensive distribution, high clearance and short half-life over a range of IV doses. It is rapidly and completely absorbed following IM or SQ administration.
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    Impact of phosphorus availability on modelling phytoplankton dynamics (1986)
    Springer
    Aquatic ecology 20 (1986), S. 225-243 
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    ISSN: 1573-5125
    Keywords: phosphorus ; bioavailability ; nutrient/phytoplankton modelling ; eutrophication
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Regulation of phosphorus loading is considered to be the primary method of eutrophication control for many lake systems. It is therefore necessary to have accurate estimates of the forms and bioavailability of all phosphorus sources in order to develop the most cost effective load control measures. Research at Clarkson University, aimed at improving the accuracy of estimates of the form and reactivity of phosphorus loadings to Lake Erie, has revealed a significant difference between the algal-availability of allochthonous and autochthonous particulate phosphorus. This paper presents the results of modifying an existing multi-nutrient phytoplankton model by separating allochthonous phosphorus into three forms: soluble reactive phosphorus (SRP) — immediately available for algal uptake; external ultimately-available phosphorus—not immediately available but converted to an available form at a specific rate; an external refractory phosphorus (ERP)—not available while in the water column. Comparisons between the original and modified models showed that the modified phosphorus dynamics proved to be a viable alternative to the concept of invoking an unexplained soluble phosphorus water column loss term, employed in the original model. The work also demonstrates that the distinction is significant for lakes receiving a significant portion of their external phosphorus load in a particulate (not immediately available) form and having a morphometry and hydrology such that this particulate phosphorus remains in the water column for longer than about two weeks.
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    URL: http://dx.doi.org/10.1007/BF02291165
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    The impact of neglecting nonlinear plasma-protein binding on disopyramide bioavailability studies (1986)
    Springer
    Journal of pharmacokinetics and pharmacodynamics 14 (1986), S. 365-379 
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    ISSN: 1573-8744
    Keywords: disopyramide ; bioavailability ; protein binding ; nonlinear ; sustained release ; pharmacokinetics ; ultrafiltration ; immunoassay
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Disopyramide has nonlinear protein binding and thus the relationship between the extent of its bioavailability and AUC,the area under the plasma concentration-time curve, is (1) nonlinear and (2) absorption rate-dependent. The unbound species follows linear pharmacokinetics. A solution of disopyramide, the innovator's product, and two generic formulations were found to be statistically indistinguishable in their bioavailability of disopyramide, whether comparison was based upon AUCor area under the plasma unbound concentration-time curve (AUCu).The AUCand AUCugave similar results because of truly similar bioavailability, coupled with sufficiently similar release rates, among the four preparations chosen for study. The concentration dependence of disopyramide protein binding and the time course of unbound plasma concentrations were fit by models which then allowed prediction of AUCunder various biopharmaceutical scenarios. Nonlinear binding of disopyramide to plasma proteins renders AUCan insensitive parameter for the discrimination of products with different extents of bioavailability; immediate release products allowing bioavailabilities of 75 or 125% relative to the solution can generate AUCs86 and 112%, respectively, of that from the solution. Nonlinear binding, furthermore, leads to a tendency for AUC tooverestimate the bioavailability of slower release products in single-dose studies; if AUCwere the index of bioavailability, products permitting the same bioavailability as the solution but releasing over 12 hr could appear to allow 114% relative bioavailability. Moreover, in some situations the bias arising from the insensitivity of AUCto product differences can be reinforced by the dependence of AUCon release rate; an apparent relative bioavailability of 80% can be achieved by a 12-hr release product allowing a true relative bioavailability of a mere 58%. While multiple-dose studies appear largely to avoid the tendency to overestimate low bioavailability in slow-release products, in these studies AUCappears to be even more insensitive in resolving discrepancies between products. Assay technology now available makes AUCua feasible and more reliable index of bioavailability than AUCwhen plasma protein binding of drugs is nonlinear.
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    On the pharmacokinetics of 16-acetyl-gitoxin and its bioavailability from pengitoxin-containing tablet formulations (1986)
    Springer
    Journal of pharmacokinetics and pharmacodynamics 14 (1986), S. 357-364 
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    ISSN: 1573-8744
    Keywords: 16-acetyi-gitoxin ; pengitoxin ; pharmacokinetics ; bioavailability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract In six volunteers the pharmacokinetics of 16-acetyI-gitoxin (16AG, 0.5mg) administered intravenously (A1) and as an oral solution (A2) and of pengitoxin (PAG, 0.6 mg) administered intravenously (A3) was evaluated. In six volunteers the bioavailability of 16AG from two PAG tablet formulations (1.2 mg) (B2, B3) was measured by comparison with the absorption after administration of a pengitoxin solution (1.2mg) (B1). In both studies the test was performed using a crossover design. After a single i.v. injection of equimolar doses, 16AG and PAG showed similar mean kinetic parameters: t 1/2 =51.6hr (16AG) and 60.8 hr (PAG), CL=11.7ml min−1 (16AG) and 12.7ml min−1 (PAG), CLR=4.1 ml min−1 (16AG) and 4.2ml min−1 (PAG). The 16AG was absorbed from solution with a mean half-life of 0.2hr to an extent of 98.6%. The mean urinary excretion /Ae(0, 4)/ of 16AG amounted to 24.6% (A1), 20.8% (A2) and 28.1% (A3). On the basis of AUCvalues, the mean bioavailability of PAG from either tablet formulation amounted to 79.6% (B2) and 89.6% (B3). The pharmacokinetic parameters of 16AG (PAG) are closer to those of digitoxin than those of digoxin. In general, 16AG is characterized as a digitoxin with a digoxin-like elimination half-life.
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    A dispersion model of hepatic elimination: 1. Formulation of the model and bolus considerations (1986)
    Springer
    Journal of pharmacokinetics and pharmacodynamics 14 (1986), S. 227-260 
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    ISSN: 1573-8744
    Keywords: dispersion model ; hepatic elimination ; bolus ; well-stirred model ; parallel-tube model ; distributed model ; protein binding ; hepatic cellular activity ; cellular permeability ; blood flow ; bioavailability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A dispersion model of hepatic elimination, based on the residence time distribution of blood elements within the liver, is presented. The general rate equations appropriate for describing the hepatic output concentration of a tracer solute are derived. Particular consideration is given to events following a bolus input dose of a tracer. The model is shown to be compatible with the known hepatic architecture and hepatic physiology. The model has been fitted to hepatic outflow data for red blood cells, albumin, and other noneliminated solutes. The experimental data suggest a high degree of dispersion of blood elements within the liver. The model has also been used to evaluate the effects of changes in enzyme activity, hepatic cell permeability, blood flow, and protein binding on the outflow concentration vs. time profiles of solutes.
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    Bioavailability of Propranolol After Oral, Sublingual, and Intranasal Administration (1986)
    Springer
    Pharmaceutical research 3 (1986), S. 108-111 
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    ISSN: 1573-904X
    Keywords: propranolol ; intranasal ; sublingual ; absorption ; bioavailability ; pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The bioavailability of propranolol was compared after oral, sublingual, and intranasal administration in eight healthy male volunteers. Relative to the bioavailability after intranasal (in) administration, which was previously shown to be nearly complete (F relin = 100%), the sublingual (sl) administration of a standard 10-mg tablet gave a bioavailability of F relsl = 63 ± 22%, while the oral (or) administration yielded only F relor = 25 ± 8%. The serum concentration–time curves of propranolol after sublingual administration resembled those of a sustained-release preparation. This sustained-release phenomenon after the sublingual route is reflected in the mean residence times (MRTs) of propranolol in the body (MRTor = 5.7 ± 1.3 hr, MRTsl - 6.4 ± 1.3 hr, MRTin = 4.6 ± 1.0 hr; mean ± SD; N = 8). MRTs after sublingual administration were significantly longer than after the oral and the intranasal doses (P 〈 0.05 and P 〈 0.002, respectively).
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    Absorption of glibenclamide from different sites of the gastro-intestinal tract (1985)
    Springer
    European journal of clinical pharmacology 29 (1985), S. 193-197 
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    ISSN: 1432-1041
    Keywords: Glibenclamide ; intestinal absorption ; small and large intestine ; bioavailability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary In a study of eight volunteers and six patients, glibenclamide was placed at different sites of the gastro-intestinal tract under visual control. The dose was instilled once into the stomach and once into the duodenum of the eight volunteers in a randomized crossover design. The six patients underwent diagnostic colonoscopy, and the dose was placed into the ascending colon if pathological findings were not present. The area under the concentration-time curve, completed by extrapolation, and the mean residence time of the drug in the body were calculated. These pharmacokinetic characteristics were examined using a Jonckheere test for ordered alternatives and a Wilcoxon signed rank pair test. The means of the areas under the curve were 477±131 ng·h ml−1 for the stomach, 475±142 ng·h ml−1 for the duodenum and 486±301 ng·h ml−1 for the colon. The mean residence time changed from 2.67±0.35 h for the stomach to 2.42±0.48 h for the duodenum and 3.55±0.68 h for the colon. These results indicate that although glibenclamide is absorbed from all three sites of the gastro-intestinal tract to the same extent, the rates of absorption are different. It is discussed whether these findings really confirm the pH-partition hypothesis in drug absorption. Since glibenclamide — a weak acid — has a pK-value of about 6.5, these data seem to confirm the pH-partition hypothesis of drug absorption.
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    Effect of two antacids on the bioavailability of paracetamol (1985)
    Springer
    European journal of clinical pharmacology 29 (1985), S. 251-253 
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    ISSN: 1432-1041
    Keywords: paracetamol ; antacids ; acetaminophen ; bioavailability ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The effect of two antacids on the bioavailability of paracetamol has been investigated in 12 young healthy volunteers. Following a random cross over design, each subject swallowed, on three separate occasions, one weak apart, 500 mg paracetamol alone, or together with two different aluminium hydroxide, magnesium hydroxide preparations (Dimalan and Maalox). Plasma paracetamol levels were measured by HPLC. The bioavailability of paracetamol was not altered by either antacid, but they both delayed the time to peak plasma concentration (0.85 h; 1.43 h; 1.25 h, without antacid, with Dimalan and with Maalox respectively). The peak plasma concentration was not affected by concurrent antacid administration.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00547432
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    Intramuscular bioavailability of chlorazepate as compared to diazepam (1985)
    Springer
    European journal of clinical pharmacology 28 (1985), S. 229-230 
    Details
    ISSN: 1432-1041
    Keywords: diazepam ; dipotassiumchlorazepate ; benzodiazepines ; bioavailability ; administration ; healthy volunteers
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Dipotassium chlorazepate (DPC) and diazepam (DZM) were given i.m. and i.v. to 6 healthy volunteers in doses of 20 mg (48.9 µmol) DPC and 15 mg (52.0 µmol) DZM. The interval between the injections was at least 1 week. Plasma samples were analyzed for DPC and DZM by HPLC. The bioavailability of DPC and DZM after i.m. administration, determined from computer calculated AUCs, was 1.04 and 0.85, respectively.
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    URL: http://dx.doi.org/10.1007/BF00609698
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    Pharmacokinetics of oral moclobemide in healthy human subjects and effects on MAO-activity in platelets and excretion of urine monoamine metabolites (1985)
    Springer
    European journal of clinical pharmacology 28 (1985), S. 89-95 
    Details
    ISSN: 1432-1041
    Keywords: moclobemide ; Ro 11-1163 ; pharmacokinetics ; bioavailability ; MAO activity in platelets ; monoamine metabolites in urine ; healthy volunteers
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The plasma concentrations of the MAO-inhibitor moclobemide (Ro 11-1163) were determined in six healthy male subjects after oral (tablets) administration. Effects on MAO activity in platelets and excretion of monoamine metabolites in urine were investigated. The design of the study was a double-blind cross-over study with single oral doses of placebo, 50, 100 and 200 mg of moclobemide. The elimination profile of the drug showed that the half life of the unchanged drug ranged between 1 and 2 h except in one subject with a half-life of about 4 h. The mean bioavailability calculated using flow model concepts was F=0.43 after 50 mg, F=0.47 after 100 mg and F=0.59 after 200 mg. The outlier with a t1/2 of 4 h was found to have a bioavailability of more than 0.80 after all 3 doses. The slightly increasing bioavailability with higher doses was interpreted as evidence of saturable hepatic first-pass elimination of the drug. MAO activity in platelets was measured before and 2, 6 and 24 h after drug administration. No inhibition of platelet MAO was obtained at any point in time or dose level, as to be expected since moclobemide preferentially inhibits MAO A. Urine excretion of the monoamine metabolites homovanillic acid (HVA), dihydroxyphenylacetic acid (DOPAC), 3-methoxy-4-hydroxy-phenylglycol (MOPEG) and 5-hydroxyindoleacetic acid (5-HIAA) was followed during 48 h after placebo, 50 and 200 mg of moclobemide. Time but not dose contributed significantly to the variability in excretion of the monoamine metabolites. An apparent reduction of HVA and DOPAC levels was obtained in the early phase after the administration of 200 mg of moclobemide. In 1 subject with a mild drug reaction a pronounced decrease in the levels of all the metabolites was obtained. In the other 5 subjects, the compound was very well tolerated with a few reported side-effects like increased activity, somnolence or sweatings. There was a slight but significant increase in blood pressure following 50 and 100 mg but not 200 mg of moclobemide.
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    URL: http://dx.doi.org/10.1007/BF00635714
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    Bioavailability and diuretic effect of furosemide during long-term treatment of chronic respiratory failure (1985)
    Springer
    European journal of clinical pharmacology 28 (1985), S. 53-59 
    Details
    ISSN: 1432-1041
    Keywords: furosemide ; respiratory failure ; furosemide glucuronide ; first-pass metabolism ; diuretic effect ; bioavailability ; food effect ; chronic treatment
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The bioavailability and diuretic effect of furosemide 40 mg administered orally for at least 6 months have been compared in patients with chronic respiratory failure and in healthy controls. The mean urinary recovery of unchanged drug was 11.5 mg and 9.41 mg in 24 h after pre- and postprandial administration to 10 patients, whereas the recovery was 14.4 mg in 10 healthy subjects. The diuretic effect, in terms of urine flow and sodium ion excretion in the 6 h after administration, was also less in patients than in healthy subjects. This was ascribed to the lower bioavailability of furosemide in patients, based on the urinary recovery of unchanged drug, and not to a lower level of response to furosemide than in healthy subjects. The mean absolute bioavailability of furosemide in 6 patients was 41.3% and 63.4%, respectively, calculated from unchanged drug and total drug (unchanged plus glucuronide conjugate). Approximately 53.9% of the dose of furosemide was excreted as the glucuronide conjugate after oral administration, and 34.2% after i.v. injection in the 6 patients. In 3 of the 6 patients studied, a distinct first-pass effect for glucuronidation of furosemide was observed after oral administration. In another study, the mean glucuronide fraction recovered in 24-h urine was 20.7% and 7.3% (p〈0.01) in 38 patients and 12 healthy subjects, respectively. The fraction in urine was not affected by changing the dose of furosemide from 20 to 120 mg. The lower bioavailability in patients as compared to healthy subjects is ascribed to enhanced glucuronidation and incomplete drug absorption.
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    URL: http://dx.doi.org/10.1007/BF00635708
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  • 83
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    Generalization of distribution – Free confidence intervals for bioavailability ratios (1985)
    Springer
    European journal of clinical pharmacology 28 (1985), S. 85-88 
    Details
    ISSN: 1432-1041
    Keywords: bioavailability ; distribution-free statistical method ; confidence limits
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The confidence interval approach to bioavailability assessment depends first on selection of the confidence level, usually 95%, and then determination of the confidence limits for the expected bioavailability ratio AUC(Test)/AUC(Reference). In practice, however, it is sometimes of greater interest to know the probability that the expected bioavailability will fall below a critical value, for example 0.75, or within a clinically set bioequivalence range, for example 0.80 to 1.25. Up to now, posterior probability distributions have been suggested, based on classical analysis of variance (ANOVA) with its rather restrictive assumptions, including that of a (logarithmic) normal distribution. In this report, a distribution-free confidence interval based on the Wilcox-on signed-rank statistic has been generalized so that confidence probabilities can be obtained for any given confidence limits. In the case of unimodal and almost symmetrical sampling distributions, the results obtained are very similar to those of the ANOVA-based posterior probability distribution. However, skewed or multimodal sampling distributions are better reflected by the proposed distribution-free method, and more valid information is obtained in these cases, as demonstrated by examples.
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    URL: http://dx.doi.org/10.1007/BF00635713
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    Pharmacokinetics and metabolism of isosorbide-dinitrate after intravenous and oral administration (1985)
    Springer
    European journal of clinical pharmacology 27 (1985), S. 637-644 
    Details
    ISSN: 1432-1041
    Keywords: isosorbide-dinitrate ; pharmacokinetics ; analytical method ; bioavailability ; drug metabolism
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The bioavailabilities of a conventional and two slow release 20 mg isosorbide dinitrate (ISDN) formulations were compared after oral administration in a three way cross-over study in 8 male volunteers. In a further group of 6 male volunteers the pharmacokinetics and metabolism of ISDN were investigated after intravenous infusion of a median dose of 14.1 mg for 2.5 h. A new analytical procedure was developed for the determination of isosorbide-5-mononitrate-2-glucuronide (IS-5-MN-2-Glu) and of isosorbide (IS). Kinetic data analysis on a molar basis was performed by the program package KINPAK providing model independent parameters. The median elimination half-lives of ISDN, IS-5-MN, IS-2-MN and IS-5-MN-2-Glu were 0.7, 5.1, 3.2 and 2.5 h, respectively. The systemic clearance of ISDN was 3.7 l/min and the distribution volume 2521 (3.1 l/kg). Apart from IS-5-MN-2-Glu, with a renal clearance of 5.9 l/min which suggested substantial glucuronidation in the kidney, the renal clearances of ISDN, IS-5-MN, IS-2-MN and the corresponding amounts excreted were negligible. 27.8% of the administered ISDN was excreted as IS-5-MN-2-Glu (8.7%) and IS (19.1%). Calculations based on the two mononitrate metabolites formed from ISDN showed an incomplete recovery of 84.1%, leading to the assumption that a simultaneous denitration to IS must have occurred. The rate of denitration at each nitro group in ISDN was almost twice as high as for the same position in the corresponding mononitrate. The bioavailability of the conventional ISDN formulation was 19%, although complete absorption was indicated by comparison of the percentages of mononitrate metabolites formed after the different routes of administration. On the same basis the absorption of the two sustained release formulations was found to be poor.
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    Human plasma and skin blister fluid levels of griseofulvin following a single oral dose (1985)
    Springer
    European journal of clinical pharmacology 29 (1985), S. 109-113 
    Details
    ISSN: 1432-1041
    Keywords: griseofulvin ; skin blister fluid levels ; pharmacokinetics ; healthy subjects ; bioavailability ; protein binding
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Griseofulvin and 6-demethylgriseofulvin (6-DMG) in plasma, suction blister fluid (SBF) and cantharides blister fluid (CBF) and urinary excretion of 6-DMG, were evaluated following administration of single oral doses of an ultramicrosize and a microsize formulation of griseofulvin to 6 healthy volunteers. The bioavailability of griseofulvin was higher following the ultramicrosize formulation when 64% of the dose was recovered (via metabolites) versus 52% after the microsize preparation. Penetration into skin blister fluid was delayed as compared to plasma levels; the peak concentration in plasma was observed at 3–4 h, whereas griseofulvin in CBF increased up to 6 h. The terminal half-live was calculated from plasma levels to 9.3 h. The half-lives calculated from SBF and CBF concentrations were 9.2 and 9.8 h, respectively, (n=5). In plasma 84% of griseofulvin was bound to proteins, predominantly to albumin; binding in SBF and CBF was 72 and 82%, respectively. 3 h after drug administration the free concentration in plasma significantly exceeded the free concentrations in SBF and CBF. Distribution equilibrium between plasma and skin blister fluid was observed after 27 h. Thus, during chronic administration, the plasma griseofulvin level should reflect its concentration in the target organ.
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    URL: http://dx.doi.org/10.1007/BF00547378
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    Human plasma and skin blister fluid levels of griseofulvin after its repeated administration (1985)
    Springer
    European journal of clinical pharmacology 29 (1985), S. 351-354 
    Details
    ISSN: 1432-1041
    Keywords: griseofulvin ; skin blister fluid ; plasma concentration ; blister fluid concentration ; pharmacokinetics ; microsize formulation ; urinary excretion ; bioavailability ; different formulations
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Griseofulvin was administered orally to 6 healthy volunteers for 6 days. The subjects received 500 mg of a microsize formulation and 330 mg of an ultramicrosize formulation, according to a cross-over design. The drug was determined in plasma, suction blister fluid (SBF) and cantharides blister fluid (CBF) following the last dose. Urinary excretion of the main metabolites 6-demethylgriseofulvin (6-DMG) and its glucuronic acid conjugate was also measured. The pharmacokinetic parameters were compared with those obtained from a recent single dose experiment. On repeated administration, the bioavailability of griseofulvin was significantly lower from the microsize formulation; the urinary recovery of total 6-DMG was 33.8% versus 53.6% on administration of the ultramicrosize material. Bioavailability was reduced as compared to ingestion of a single dose. The reduction was more prominent following the microsize (36%) than the ultramicrosize (17%) formulation. Penetration into skin blister fluid was not altered as compared to the single dose experiment. Relative areas under the blister fluid-time curves amounted to 51% (SBF) and 80% (CBF) of the area under the plasma level-time curve. The concentration of unbound griseofulvin in these body fluids was identical throughout the entire dosage interval. Unbound griseofulvin levels were low in comparison with the minimum inhibitory concentrations for strains of trichophyton and microsporum.
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    URL: http://dx.doi.org/10.1007/BF00544093
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    A non-parametric confidence interval method (1985)
    Springer
    European journal of clinical pharmacology 29 (1985), S. 379-381 
    Details
    ISSN: 1432-1041
    Keywords: confidence intervals ; bioavailability ; Bayesian analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00544099
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  • 88
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    Nasal bioavailability and systemic effects of the glucocorticoid budesonide in man (1985)
    Springer
    European journal of clinical pharmacology 29 (1985), S. 477-481 
    Details
    ISSN: 1432-1041
    Keywords: budesonide ; glucocorticoid ; nasal administration ; pharmacokinetics ; bioavailability ; systemic effects
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Budesonide, a topically potent glucocorticoid, was administered to 4 healthy volunteers by i.v. infusion and by nasal instillation of 100 µg tritium-labelled drug. Plasma was analyzed by liquid chromatography plus scintillation counting of collected fractions. After i.v. administration the plasma clearance was 0.92 l/min and the apparent volume of distribution was 2.8 l/kg. After nasal administration, the time to reach the peak plasma level was approximately 30 min, and the systemic availability was 102%. Budesonide had marginal effects on plasma cortisol and white blood cell counts either after i.v. or nasal administration. Thus, nasally instilled budesonide in solution is rapidly and completely absorbed from the nasal mucosa. The systemic effects after this clinically recommended nasal dose were negligible.
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    URL: http://dx.doi.org/10.1007/BF00613465
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    Bioavailability and pharmacokinetics of ketanserin in elderly subjects (1985)
    Springer
    European journal of clinical pharmacology 28 (1985), S. 411-417 
    Details
    ISSN: 1432-1041
    Keywords: ketanserin ; ketanserinol ; pharmacokinetics ; age ; healthy volunteers ; bioavailability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The bioavailability of ketanserin has been examined in a cross-over experiment in 21 elderly subjects (aged 59–72 years) by administration of tablets (40 mg), solution (40 mg) and injectable solution (10 mg). After two weeks of treatment with 40 mg ketanserin tablets further 18 blood samples for analysis were collected under steady-state conditions. Plasma levels were measured by HPLC. The absolute bioavailability of ketanserin tablets was 52.7%; their relative bioavailability compared to a solution containing an equal quantity of active compound was 85.5%. Therefore, the low absolute bioavailability of ketanserin cannot be attributed to the formulation. The active compound was rapidly liberated from the tablet, reaching a peak of 103.8 ng/ml after 0.97 h. Individual plasma level-time curves were fitted to an open three compartment model and a half-life of 17.7±7.26 h was calculated for the terminal elimination phase. An average terminal elimination half-life of 15.4±4.2 ng/ml was found after administration of the ketanserin solution. Multiple dosing with 40 mg tablets b.d.s. resulted in an AUC over one dosing interval at steady-state of 666±201 ng × h/ml. The AUC extrapolated to infinity was 1200±405 ng × h/ml for the last tablet. This is 1.8-times the AUC in one dosing interval, and 2.3-times the AUC of a single dose. Under steady-state conditions, the mean peak plasma level was 155.1 ng/ml (1.08 h after dosing) and the terminal half-life was 19.1±5.1 h. For the metabolite ketanserinol terminal half-lives of 21.4 h after a single tablet and 31.0 h after discontinuation of multiple dosing were calculated. Compared to the parent compound there was much more marked accumulation of ketanserinol. Despite moderate accumulation and prolongation of the terminal half-life of ketanserin under steady-state conditions, dosage adjustment is not required in elderly people. First-pass metabolism and bioavailability remained in the range found in previous studies of ketanserin in young subjects.
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    URL: http://dx.doi.org/10.1007/BF00544359
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    The influence of ascites on the pharmacokinetics of piretanide in cirrhotic patients (1985)
    Springer
    European journal of clinical pharmacology 28 (1985), S. 581-583 
    Details
    ISSN: 1432-1041
    Keywords: piretanide ; liver cirrhosis ; ascites ; bioavailability ; pharmacokinetics ; diuretic
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The pharmacokinetics of piretanide, a new loop diuretic, were studied in seven patients with severe liver disease before and after resolution of ascites. The time to maximum concentration was significantly prolonged by the presence of ascites. Tmax after relief of ascites was similar to that seen for normal volunteers. Area under the curves, bioavailability, volumes of distribution and elimination half-lives did not change after resolution of the ascites: two patients in whom diuretic resistant ascites occurred showed similar pharmacokinetics to that of the diuretic responders. Reduced responsiveness to piretanide therapy in patients with gross ascites does not appear to be the result of decreased bioavailability.
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    New method for bioavailability assessment of slow-release preparations of theophylline (1985)
    Springer
    Journal of pharmacokinetics and pharmacodynamics 13 (1985), S. 571-587 
    Details
    ISSN: 1573-8744
    Keywords: theophylline ; bioavailability ; variability in clearance ; siow-release preparations ; urinary metabolites
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Variability in an individual's clearance of theophylline is an important consideration when estimating bioavailability. A method is described for compensating for this problem, using the serum concentration of theophylline and urinary excretion data on its major metabolites to make an estimation of the clearance after oral administration using the intravenous dose as reference. The method is particularly useful for assessing the bioavailability of slow-release theophylline preparations.
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    URL: http://dx.doi.org/10.1007/BF01058902
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    A nonlinear physiologic pharmacokinetic model: I. Steady-state (1985)
    Springer
    Journal of pharmacokinetics and pharmacodynamics 13 (1985), S. 73-92 
    Details
    ISSN: 1573-8744
    Keywords: pharmacokinetic theory ; venous equilibration (“well-stirred”) model ; compartment model ; linear pharmacokinetics ; nonlinear pharmacokinetics ; bioavailability ; intrinsic clearance ; liver blood flow ; clearance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The two-compartment model of Rowland et al.,(2) has been extended by replacing first order elimination with Michaelis-Menten elimination kinetics. All of the equations for steady-state concentrations and clearances for zero order (constant rate) input orally (into compartment #2) and intravenously (into compartment #1) are derived and reported. The steady-state concentration in compartment #1, following intravenous administration, is shown to be a nonlinear function of maximal velocity of metabolism, Vm,the Michaelis constant, Km,and liver blood flow, Q;and, following oral administration is dependent only upon Vm and Km and is independent of Q.However, oral bioavailability is a function of Vm, Km,and Q.The model allows physiologic pharmacokinetic interpretation of both linear and nonlinear data; and, together with simple modification of the model, can explain much observed pharmacokinetic data to date particularly for first-pass drugs. Future articles in the series will be concerned with single doses, evaluation of literature data in terms of the model, application of the theory in toxicology and in clinical pharmacokinetics and therapeutics.
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    Distribution, elimination, metabolism and bioavailability of hexamethylenebisacetamide in rats (1985)
    Springer
    Investigational new drugs 3 (1985), S. 263-272 
    Details
    ISSN: 1573-0646
    Keywords: HMBA ; hexamethylenebisacetamide ; bioavailability ; toxicity ; pharmacodynamics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Hexamethylenebisacetamide (HMBA), an in vitro differentiating agent, was studied for its pharmaco-dynamic actions in animals. Plasma stability, organ distribution, excretion, oral bioavailability, and estimates of pharmacokinetic parameters and acute lethality were determined in rats. The single dose intraperitoneal LD50 was greater than 3000 mg/kg in both mice and rats. The drug was stable in plasma from several different species during an 8 h in vitro incubation at 37°C. Following a single intravenous (iv) bolus injection (1000 mg/kg) to rats, HMBA was removed from the plasma with a half time of 2.2 ± 0.5 h, and 65 ± 8% of the dose was excreted unchanged in the urine during the first 24 h after dosing. During an 8 h iv infusion, plasma concentrations of 4 mM were easily maintained with no apparent adverse effects. Drug was uniformly distributed, with highest concentrations found in thymus, kidney, liver, and lymph node throughout the first 24 h after a single iv bolus dose. In vivo metabolism was very small, and the presence of apparent metabolites was undetectable until 48 h after iv administration. Oral bioavailability was good (32%), with peak plasma concentrations of 2 mM achieved one hour after oral administration. After oral dosing urinary excretion and plasma decay were comparable to similar data obtained after iv dosing.
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    Pharmacodynamics and pharmacokinetics of xipamide in patients with normal and impaired kidney function (1984)
    Springer
    European journal of clinical pharmacology 26 (1984), S. 513-520 
    Details
    ISSN: 1432-1041
    Keywords: xipamide ; electrolyte excretion ; bioavailability ; elimination ; extrarenal clearance ; chronic renal failure ; furosemide ; hydrochlorothiazide ; amiloride
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The effect of a single oral dose of 40 mg xipamide on urinary excretion of Na+, K+, Cl−, Ca2+ and Mg2+ in healthy subjects and in patients with varying degrees of renal impairment was compared with various conventional diuretics. Xipamide caused marked excretion of Na+ and Cl−, whereas the diuretic produced only moderate kaliuresis; urinary excretion of Ca2+ was increased in proportion to Na+, like the loop diuretics. Xipamide affected electrolyte excretion even in patients with a creatinine clearance below 30 ml/min, as do the loop diuretics, too. Therefore, the pharmacodynamic characteristics of xipamide are more like those of a loop diuretic than of a thiazide. Xipamide was good bioavailable, its t1/2β was 7 h and urinary recovery of the undegraded drug was 40% of the given dose. In renal insufficiency, t1/2β increased from 7 to only 9 h, yielding a moderate increase in the AUC. Urinary recovery of the drug was reduced in proportion to the reduction in the creatinine clearance of the patient. Therefore, significant extrarenal elimination of the diuretic must be postulated, which suffices to prevent significant drug accumulation in renal failure.
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    Bioavailability and pharmacokinetics of phenytoin during pregnancy (1984)
    Springer
    European journal of clinical pharmacology 27 (1984), S. 105-110 
    Details
    ISSN: 1432-1041
    Keywords: phenytoin ; epileptic women ; pharmacokinetics ; bioavailability ; pregnancy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Five epileptic women needing to commence phenytoin therapy during pregnancy received a single intravenous and a single oral dose of phenytoin several days apart before starting regular intake of the drug. Plasma phenytoin concentration — time data were analysed by three different pharmacokinetic techniques. However assessed, the mean oral bioavailability of the drug proved to be about 90% of the intravenous bioavailability. This finding makes it unlikely that impaired bioavailability accounts for the increase in oral phenytoin dosage necessary in pregnancy to maintain plasma phenytoin concentrations at pre-pregnancy values. Phenytoin clearance in the pregnant subjects was approximately double the published values for phenytoin clearance in nonpregnant persons. This suggests that increased (metabolic) clearance accounts for the increased phenytoin dosage requirement of pregnancy.
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    URL: http://dx.doi.org/10.1007/BF02395215
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    Implications of intraindividual variability in bioavailability studies of furosemide (1984)
    Springer
    European journal of clinical pharmacology 27 (1984), S. 595-602 
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    ISSN: 1432-1041
    Keywords: furosemide ; bioavailability ; generic tablet formulations ; intrasubject variability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Intrasubject variation in bioavailability (rate and extent) and disposition of furosemide 40 mg was investigated using a repeated, randomized, double-blind cross-over study in 8 healthy subjects. Two generic tablet formulations (Lasix and Furix) and intravenous furosemide were compared on 6 separate days. Extensive intrasubject variability after oral administration was observed in AUC, mean absorption time (MAT) and urinary excretion. The variability (error variance) within the dosage forms was as large as that between the two generics. These variations most probably depended on the absorption process, since the repeated i.v. doses showed only marginal intrasubject variability. Absolute bioavailability was 56% for Lasix and 55% for Furix (AUC). The range was 20 to 84% between individuals and the maximal range within one individual was 20 to 61%. Confidence interval and Bayesian analysis showed a high probability of non-equivalence not only between but also within the generics when the separate cross-over experiments were analyzed (8 observations). When extending the analysis to 16 observations, bioequivalence was demonstrated for the two generic tablets. Rate of absorption, quantified as MAT, was 128 min for Lasix and 98 min for Furix (16 observations). Since MAT was significantly longer (p〈0.001) than the mean residence time after the i.v. dose (57 min), absorption was evidently the rate-limiting step in the overall kinetics of oral furosemide. Intraindividual variation in absorption is a confounding factor in bioavailability studies of furosemide using limited numbers of subjects. This is important to consider when designing and evaluating bioavailability studies for drugs showing these variations.
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    Food does not effect in bioavailability of theophylline from Theolin Retard® (1984)
    Springer
    European journal of clinical pharmacology 26 (1984), S. 405-407 
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    ISSN: 1432-1041
    Keywords: theophylline ; drug absorption ; bioavailability ; food intake ; sustained-release preparations ; Theolin Retard
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The absorption of theophylline from a sustained release tablet preparation (Theolin® Retard 300 mg) was studied in 10 subjects both when fasting and immediately after a standardized breakfast. Intravenous aminophylline was used as the reference material. Food did not influence the absorption from Theolin Retard. The bioavailability was complete (93% after 30 h) both with and without food, and no difference was found in the time to peak of the plasma concentration curve (7 h), or the mean residence time (14 h). The absorption characteristics, with predominantly zero order kinetics, did not change with concomitant intake of breakfast.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00548776
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  • 98
    Electronic Resource
    Electronic Resource
    Effect of food on pharmacokinetics of chlorambucil and its main metabolite, phenylacetic acid mustard (1984)
    Springer
    European journal of clinical pharmacology 27 (1984), S. 111-114 
    Details
    ISSN: 1432-1041
    Keywords: chlorambucil ; chronic lymphocytic leukaemia ; phenylacetic acid mustard ; food intake ; pharmacokinetics ; bioavailability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The influence of food intake on the pharmacokinetics of chlorambucil (C) and its cytotoxic metabolite, phenylacetic acid mustard (PAM), has been studied in man after oral doses of chlorambucil. The administration of chlorambucil with food resulted in slower absorption than when fasting. However, the area under the plasma concentration-time curve (AUC) was unaffected. The mean ratio AUCPAM/AUCC was 2.8 (range 1.4–7.1) under fasting and 3.3 (range 1.3–7.4) under nonfasting conditions. The metabolite very probably plays an important role in the cytotoxic effects observed after administration of C, since calculations show that a major fraction of the metabolite is eliminated by alkylation reactions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00553164
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  • 99
    Electronic Resource
    Electronic Resource
    Studies of the bioavailability of nitroglycerin from a transdermal therapeutic system (Nitroderm TTS) (1984)
    Springer
    European journal of clinical pharmacology 27 (1984), S. 7-12 
    Details
    ISSN: 1432-1041
    Keywords: nitroglycerin ; plasma concentration ; transdermal administration ; bioavailability ; pharmacodynamics ; healthy volunteers
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary In 6 healthy volunteers, intravenous infusions of nitroglycerin 4.8 and 10.6 µg/min yielded mean steady-state plasma concentrations of 0.5±0.02 and 0.82±0.04 ng/ml as determined by a gas chromatographic/mass spectrometric method. The plasma concentrations reached in the same subjects 17 h after application of Nitroderm TTS 5 and 10 with in vivo release rates of 3.7 and 5.7 µg/min were 0.28±0.01 and 0.37±0.01 ng/ml, respectively. Thus, 75% of the quantity of nitroglycerin released by the systems passed into the circulation. The inter-individual and intra-individual variations in plasma concentrations were similar for both modes of administration. The nitroglycerin-induced morphological changes in the fingerpulse wave were clearly dose-dependent, but it seems that this pharmacodynamic parameter is determined less by the plasma concentration than by the nitroglycerin content of the vascular wall.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02395198
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  • 100
    Electronic Resource
    Electronic Resource
    Steady state bioavailability of a new oral formulation of Hydergine® in geriatric patients (1984)
    Springer
    European journal of clinical pharmacology 26 (1984), S. 133-135 
    Details
    ISSN: 1432-1041
    Keywords: co-dergocrine mesylate ; geriatric patients ; hydergine ; bioavailability ; steady state
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The relative bioavailability of the newly developed formulation of co-dergocrine mesylate (Hydergine spezial, 1×4 mg) was determined in elderly patients under steady state conditions, with conventional Hydergine forte tablets (2×2 mg) as a reference. Both formulations were given once a day for 8 days in a randomised cross-over design. The areas under the curve showed that the bioavailability of the new tablet was about 30% higher (28±6.3%) than that of Hydergine forte. The peak plasma concentration was reached 3±0.9 h after administration. Because of its greater relative bioavailability higher plasma levels were found 2–24 hours after the Hydergine spezial formulation than after Hydergine forte tablets.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00546722
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