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  • bioavailability
  • Springer  (45)
  • Cambridge University Press
  • Frontiers Media
  • 2020-2022
  • 1985-1989  (17)
  • 1980-1984  (28)
  • 1975-1979
  • 1989  (17)
  • 1983  (28)
Collection
Publisher
  • Springer  (45)
  • Cambridge University Press
  • Frontiers Media
Years
  • 2020-2022
  • 1985-1989  (17)
  • 1980-1984  (28)
  • 1975-1979
Year
  • 1
    Electronic Resource
    Electronic Resource
    Springer
    European journal of nutrition 22 (1983), S. 185-194 
    ISSN: 1436-6215
    Keywords: sugar substitutes ; D-glucose ; bioavailability ; D-glucitol (D-sorbitol) ; D-mannitol ; Palatinit® ; D-glucosyl-α(1→1)-D-mannitol ; D-glucosyl-α(1→6)-D-glucitol
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Medicine
    Description / Table of Contents: Zusammenfassung Zur Vertiefung des Verständnisses vom Stoffwechsel des Zuckeraustauschstoffes Palatinit® wurden seine zwei Bestandteile D-Glucosyl-α(1→1)-D-mannit und D-Glucosyl-α(1→6)-D-glucit [D-Glucosyl-α(1→6)-D-sorbit] nach dem Verfahren von Karimzadegan et al. auf ihre Glucose-Bioverfügbarkeit an ketotischen Ratten untersucht. Bei Umwandlungsraten in Glucose von 6 bzw. 20 % für Mannit und Glucit (Sorbit) sowie von 39 bzw. 42% für Glucosylmannit und Glucosylglucit erhält demnach der metabolische Glucose-Pool nicht das volle Glucose-Äquivalent aus diesen Verbindungen. Von dem Anteil an präformierter Glucose in den Glucosylhexiten — theoretisches Maximum 50 % — sind nur 36 % aus Glucosylmannit bzw. 32 % aus Glucosylglucit bioverfügbar. Die im Vergleich zur Theorie verminderte Bioverfügbarkeit von Glucose aus Palatinit® wird auf partiellen mikrobiellen Abbau in unteren Darmabschnitten zurückgeführt. Die an Ratten erhaltenen Ergebnisse werden auch für alle anderen Spezies gelten, welche in Caecum und/oder Colon Kohlenhydrate vergären. Die Unterschiede zwischen D-Glucosyl-α(1→1)-D-mannit und D-Glucosyl-α(1→6)-D-glucit werden durch unterschiedliche Verzögerung der Glucoseresorption im Dünndarm, wo auch D-Glucit angreift, bedingt. Die Ermittlung der Glucose-Bioverfügbarkeit gewährt weitgehende Einblicke in das Schicksal von Kohlenhydraten einschließlich der Symbiose zwischen Säugetier und Mikroorganismen im Dickdarm. Da ein ziemlich vollständiger Überblick über die metabolischen Konsequenzen nach ihrer Zufuhr erhalten wird, sollte das Verfahren zur Messung der Bioverfügbarkeit von Glucose daher bei Abschätzungen der Lebensmittelsicherheit anderer Zuckeraustauschstoffe ebenfalls angewandt werden.
    Notes: Summary For the sake of metabolic insight into the fate of the sugar substitute Palatinit®, its two components D-glucosyl-α(1→1)-D-mannitol and D-glucosyl-α(1→6)-D-glucitol [D-glucosyl-α-(1→6)-D-sorbitol] were assayed for glucose bioavailability by the procedure of Karimzadegan et al. using ketotic rats. With conversion rates into glucose of 6 and 20 %, respectively, for free mannitol and glucitol (sorbitol), 39 % for glucosylmannitol and 42 % for glucosylglucitol, the metabolic glucose pool of the rat does not receive the full carbohydrate complement of these compounds. The preformed glucose moiety of the glucosylhexitols is bioavailable by 36 and 32 %, respectively, from glucosylmannitol and glucosylglucitol, with 50 % as theoretical maximum. Less than theoretical bioavailability of glucose from Palatinit® is ascribed to microbial attack in the hindgut. The data on rats are held valid also for other species demonstrating carbohydrate fermentation in the caecum and/or colon. Differences between D-glucosyl-α(1→1)-D-mannitol and D-glucosyl-α(1→6)-D-glucitol are caused by a differential delay of glucose absorption in the small intestine, also exerted by D-glucitol. The deep metabolic insight offered by the glucose bioavailability assay into the fate of carbohydrates includes the mammal-microbial symbiosis in the large bowel. Since a rather complete survey of the metabolic consequences after their intake can be obtained, the assay system should be generally applied in assessments of food safety also of other sugar substitutes.
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  • 2
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    Springer
    European journal of nutrition 28 (1989), S. 130-141 
    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.
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  • 3
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    European journal of clinical pharmacology 37 (1989), S. 409-410 
    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.
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  • 4
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    European journal of clinical pharmacology 37 (1989), S. 419-421 
    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.
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  • 5
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    European journal of clinical pharmacology 37 (1989), S. 423-426 
    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.
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  • 6
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    European journal of clinical pharmacology 24 (1983), S. 127-136 
    ISSN: 1432-1041
    Keywords: statistical analysis ; nonparametric statistical methods ; bioavailability ; confidence interval ; ANOVA
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary For a two-way cross-over design, which appears to be the most common experimental design in bioavailability studies, 95%-confidence limits for expected bioavailability can be obtained by classical analysis of variance (ANOVA). If symmetry of the confidence interval is desired about zero (differences) or unity (ratios) rather than about the corresponding point estimator, Westlake's modification can be used. Two nonparametric methods and their adaptations to bioavailability ratios are reviewed, one based on Wilcoxon's signed rank test (Tukey), and the other on Pitman's permutation test. The necessary assumptions and the merits of these procedures are discussed. The methods are illustrated by an example of a comparative bioavailability study. A FORTRAN program facilitating the procedures is available from the authors upon request.
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  • 7
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    European journal of clinical pharmacology 24 (1983), S. 791-796 
    ISSN: 1432-1041
    Keywords: furosemide ; bioavailability ; diuretic effect ; urine sodium ; urine potassium ; power of ANOVA ; tablet formulations ; urinary flow rate ; normal volunteers
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The relative bioavailability and diuretic effect of 2 commercially available tablet preparations of furosemide 40 mg was examined in 10 healthy male volunteers. A close linear relationship between the urinary excretion rate of furosemide and the rate of sodium ion excretion in urine and/or flow rate of urine was demonstrated. There were no significant differences in the urinary excretion of furosemide, sodium and potassium ions or urinary volume following the oral doses. The difference in drug content affected the urinary recovery of furosemide over 24 h but had no effect on the pharmacological response. The analytical power of ANOVA using the various parameters of the responses to furosemide was no lower than when the parameters of urinary excretion of furosemide were used.
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  • 8
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    European journal of clinical pharmacology 25 (1983), S. 237-241 
    ISSN: 1432-1041
    Keywords: triamterene ; bioavailability ; pharmacokinetics ; metabolism ; hydroxy triamterene sulphate ; urinary excretion ; i.v. administration ; first-pass-effect
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary With a new formulation, which made intravenous infusion of triamterene (TA) possible, plasma levels and urinary excretion rates of TA and its main metabolite (OH-TA-ester) were measured in a randomized, cross-over trial in 6 healthy volunteers given triamterene 10 mg i.v. and 50 mg p.o. TA and OH-TA-ester were determined by densitometric measurement of native fluorescence after thin layer chromatography. Distribution volumes of the central compartment of TA and OH-TA-ester were 1.49 l/kg and 0.11 l/kg, respectively. Terminal half-lives were 255 min for TA and 188 min for OH-TA-ester after i.v. administration. For TA total plasma clearance was 4.5 l/min and renal plasma clearance 0.22 l/kg. The formation of OH-TA-ester was very rapid and the concentration of the metabolite exceeded that of TA at all times. After i.v. administration the urinary recovery of TA and OH-TA-ester was 4.4% and 50.9%, respectively. The bioavailability of TA was 52%, corresponding to absorption of 83%. TA is partly eliminated by a first-pass-effect. The main metabolite of TA is OH-TA-ester, which is pharmacologically active.
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  • 9
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    European journal of clinical pharmacology 25 (1983), S. 449-453 
    ISSN: 1432-1041
    Keywords: canrenone ; pharmacokinetics ; plasma level ; bioavailability ; urinary excretion ; spironolactone
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Five healthy male volunteers received canrenoate-K 200 mg (Sincomen® pro injectione) by intravenous injection and one week later spironolactone 200 mg (Sincomen®-100) orally. Plasma levels and urinary excretion of unchanged canrenone were determined up to 24 h by a specific HPLC method. Following intravenous administration, the maximum plasma level of 2066±876 ng/ml was found after 29±15 min and thereafter the concentration declined with a half-life of 3.7±1.2 h. Total clearance was 4.2±1.7 ml/min·kg. After oral ingestion, the maximum concentration of 177±33 ng/ml was observed at 4.4±0.9 h. The absolute bioavailability of canrenone was 25±9%. Within 24 h, respectively 0.4 and 0.6 mg, canrenone were excreted by the kidney after intravenous and oral administration. The half-life of elimination was 4.9±1.8 h (i.v.) and 3.9±1.2 h (p.o.).
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  • 10
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    European journal of clinical pharmacology 24 (1983), S. 103-108 
    ISSN: 1432-1041
    Keywords: dexamethasone ; bioavailability ; pharmacokinetics ; ‘first-pass’ effect ; pre-systemic elimination
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The pharmacokinetics and oral biovailability of dexamethasone were studied in 6 patients with neurological disease being treated with high dosages of the drug. A specific high performance liquid chromatographic assay was used to measure dexamethasone concentrations. Unlike the previously published mean figure of 0.78 for the oral bioavailability of the drug given in single doses to healthy volunteers, the mean bioavailability of dexamethasone in the patients studied was 0.53±SD 0.40. It appeared more likely that this incomplete bioavailability was due to presystemic elimination than to poor absorption. The intravenous clearance of the drug was relatively high (0.4902±SD 2291 l kg−1, approximately 65% of expected hepatic plasma flow), the oral clearance higher (2.5804±SD 3.2181 l kg−1 h−1) while the absorption rate constant (4.8729±8.4998 h−1), suggested rapid absorption after oral administration. Prior phenytoin and possibly prior dexamethasone therapy is likely to have contributed to the higher clearance values of the drug in these patients than the values reported in healthy volunteers after single dose studies.
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  • 11
    ISSN: 1432-1041
    Keywords: oxmetidine ; pharmacokinetics ; bioavailability ; plasma half-life ; clearance ; oral dose ; i.v. dose
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The plasma concentration curves and urinary excretion of oxmetidine after administration of single i.v. (100 mg) and oral (200 mg) doses have been studied in 11 patients with peptic ulcer disease. The mean bioavailability of the drug was 70% (range 53–91%). After intravenous administration, the mean plasmat 1/2β was 3.0 h, the mean apparent volume of distribution 0.7 l/kg, the mean total plasma clearance 12.3 l/h and the mean plasma renal clearance was 0.7 l/h. Following intravenous and oral administration an average of 6% and 3%, respectively, of unchanged drug was found in the urine. The plasma concentration curve after oral administration in most patients exhibited two maxima, with peak concentrations appearing between 45 and 210 min after dosing.
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  • 12
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    European journal of clinical pharmacology 25 (1983), S. 689-693 
    ISSN: 1432-1041
    Keywords: amiodarone ; bioavailability ; calculation ; linear pharmacokinetics ; absorption
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Methods for estimating the bioavailability of drugs with long elimination half-lives are examined. Provided both absorption and disposition are linear a simple linear regression method is developed which can be used to calculate bioavailability in situations where only an incomplete estimate of the area under the curve (AUC) is available. The regression method and the traditional method of comparing the AUC following an oral dose to the AUC following an i.v. dose were applied to simulated data. It was found that the AUC ratio method works well as long as absorption is complete within the time over which the AUC is computed. The regression method is less precise than the AUC ratio method but is more accurate for drugs with long absorption half-lives. When applied to published data on a beta blocker the two methods produced comparable results. The bioavailability of amiodarone in three human subjects was calculated to be 0.20, 0.44 and 0.98 using the regression method with similar results from the ratio method. It is not possible to estimate the clearance of amiodarone from single dose data.
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  • 13
    ISSN: 1432-1041
    Keywords: chlorambucil ; prednimustine ; plasma concentrations ; bioavailability ; pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The pharmacokinetics of chlorambucil has been investigated in a cross over study after oral administration of the free drug (10 mg) and its prednisolone ester (prednimustine, 100 mg). The bioavailability of chlorambucil was about five times lower when given as prednimustine as compared to administration of the free drug. The peak plasma concentration was about twice as high and it was obtained more rapidly when the free drug was given. No intact prednimustine could be detected in plasma.
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  • 14
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    European journal of clinical pharmacology 24 (1983), S. 563-568 
    ISSN: 1432-1041
    Keywords: indomethacin ; multi-dose kinetics ; controlled release formulation ; capsule formulation ; bioavailability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The kinetics of a controlled release (CR) formulation of indomethacin 75 mg (Indocid-Retard®) given once daily was compared with a conventional 25 mg indomethacin capsule (Indocid®) given 3 times daily for 7 days, to 14 healthy volunteers, using a randomized, cross-over, multiple-dose study design. The following differences in plasma indomethacin profiles after the 2 treatments were observed: average peak concentrations (Cmax) for the CR regimen were higher and the time to peak (Tmax) was significantly delayed. Trough (pre-morning dose) plasma concentrations (Cmin) on Days 2, 5, 6 and 7 were significantly lower after the CR-formulation. No statistically significant differences between preparations for area under the plasma concentration time curve (AUC0–24h) or for renal clearance were observed. Average steady-state plasma concentrations (C p ss ) on Day 7 of the multiple dose regimens averaged 0.477 and 0.427 µg/ml for the 75 mg CR once daily and the conventional 25 mg t.i.d. treatments, respectively. These results show that the bioavailability of the CR and conventional indomethacin formulations under these multiple-dose conditions was not significantly different.
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  • 15
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    European journal of clinical pharmacology 24 (1983), S. 537-542 
    ISSN: 1432-1041
    Keywords: morphine ; analgesic activity ; tablets solution ; pharmacokinetics ; bioavailability ; pain score ; dose-response relationship ; chronic pain
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The steady-state kinetics of morphine given as tablets and solution were compared in 7 cancer patients with chronic pain. There was no accumulation of morphine (20–40 mg) when repeatedly administered every 4 to 6 h. The mean steady-state concentration of morphine during the dose interval varied between 5.9 and 68.4 ng/ml (20.7–240 nmol/l), and was linearly related to the daily dose of morphine. There were no significant differences between the tablets and the solution of morphine with regard to relative oral bioavailability or peak concentration. The time-to-maximum plasma concentrations was significantly longer for the tablets. The pain score profile, assessed by a visual analogue scale during a dose interval, showed a similar pattern after the two oral formulations of morphine. No significant linear relationship between the scores and the plasma concentrations of morphine was observed.
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  • 16
    ISSN: 1432-1041
    Keywords: metoprolol ; bioavailability ; young ; elderly ; metoclopramide ; probanthine ; gut motility
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The bioavailability of metoprolol was studied in eight healthy young and seven healthy elderly volunteers. Large interindividual differences in the bioavailability of metoprolol were observed in both groups. However, there was no significant difference in AUC, peak plasma concentration or elimination half-life between young and elderly, but time to peak concentration was significantly longer in the elderly. Pretreatment with metoclopramide had no effect on AUC but caused significant increases in peak concentration and decreases in time to peak concentration in both groups. Probanthine pretreatment (only to the young) resulted in a significant decrease in peak concentration of metoprolol and a significant increase in time to peak concentration but had no effect on the AUC. These results suggest that alterations in gastric emptying and gut motility due to ageing or other drugs have no effect on the overall availability of metoprolol to the systemic circulation but may have significant effects on the time to peak plasma concentration and peak concentration achieved after a single oral dose.
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  • 17
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    European journal of clinical pharmacology 25 (1983), S. 419-424 
    ISSN: 1432-1041
    Keywords: dihydrocodeine ; pharmacokinetics ; acid metabolites ; radioimmunoassay ; bioavailability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Serum concentrations of dihydrocodeine and its acid metabolites have been determined in seven human volunteers (6 male) who received the drug orally (30 mg and 60 mg) and intravenously (30 mg) on separate occasions, and in twenty-four patients (12 male) receiving 25 mg or 50 mg of the drug intravenously. The concentrations were estimated by radioimmunoassay on reconstituted extracts from serum after an extraction process which effectively separates dihydrocodeine from its polar acidic metabolites. The intravenous data show that dihydrocodeine kinetics followed a two-compartment distribution model. The concentration curves after oral administration indicated relatively rapid absorption with mean peak concentrations at 1.6h–1.8h. The mean half-lives varied between 3.3h–4.5h. From the AUC, the mean bioavailability of orally administered drug was 21% (range 12–34%). The peak levels of the acidic metabolites occurred between 1.8h–2.0h after oral administration and 2.2h–2.5h after i.v. administration, and they were significantly greater after oral administration. The low bioavailability of dihydrocodeine, together with the earlier and higher plasma levels of the acid metabolites after oral administration is suggestive of substantial first-pass metabolism.
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  • 18
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    European journal of clinical pharmacology 25 (1983), S. 467-473 
    ISSN: 1432-1041
    Keywords: hydralazine ; heart failure ; pharmacokinetics ; bioavailability ; metabolism ; hypertension ; dapsone ; acetylator phenotype
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The influence of various disease states, other than hypertension, on the pharmacokinetic behaviour of hydralazine is not completely known. In the present study the pharmacokinetics of oral hydralazine has been evaluated in 7 patients with severe, chronic heart failure, using 8 compensated hypertensives as controls. The pharmacokinetics was evaluated by measuring the plasma concentrations of hydralazine (“apparent” and “real” hydralazine) and hydralazine pyruvate hydrazone, and by assessing acetylator phenotype after a small dose of dapsone. The AUC (area under the plasma concentration curve) following a single, oral 50 mg dose was significantly larger in patients with chronic heart failure NYHA Class III–IV than in patients with essential hypertension without cardiac decompensation. A decreased rate of hepatic elimination of hydralazine is suggested as a major contributory factor to this finding.
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  • 19
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    European journal of clinical pharmacology 25 (1983), S. 553-556 
    ISSN: 1432-1041
    Keywords: Endralazine ; pharmacokinetic ; acetylator phenotype ; bioavailability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Endralazine (E), a new hydralazine-like antihypertensive was given intravenously (0.05 mg/kg) to 10 normal volunteers (5 slow and 5 fast acetylators). Plasma levels were fitted to a 3 compartment model and pharmacokinetic parameters (area under curve [AUC 0 ∞ ], clearance, volume of distribution, half-lives) obtained in the usual way. Bioavailabilities of 5 and 10 mg oral doses of E were determined from the AUC 0 ∞ generated in a previous study of oral E given to the same subjects. E had high system bioavailability (73.5–99.1%) suggesting that it was almost completely absorbed without undergoing appreciable first-pass metabolism. Furthermore, dose size and acetylator phenotype did not significantly affect the bioavailability of E. This behaviour contrasts with that of hydralazine where systemic bioavailability was 〈40%, and 2 to 3 times higher in slow acetylators than in fast acetylators. It is concluded that the bioavailability of E is high and not influenced by acetylator phenotype; these properties suggest some clinical advantages for the drug.
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  • 20
    ISSN: 1432-1041
    Keywords: theophylline ; asthma ; children ; sustained-release ; diurnal ; absorption ; bioavailability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The absolute oral bioavailability of a sustained release theophylline tablet (Nuelin-SR250), given 12 hourly was determined in 14 asthmatic children aged 5 to 13 years. In 4 of the patients, mean bioavailability of the fourth dose was 38.9±8.4% and that of the sixth dose was 67.9±25.9% (p〈0.05) in the other ten patients. This suggests steady-state had not been achieved after four doses. In the initial study with 9 patients, a significant diurnal variation in predose plasma theophylline concentrations was observed, as the mean morning predose concentrations were 2.9 fold greater than the mean evening predose concentrations (p〈0.005). Dual peak plasma concentrations occurred in 5 out of the 9 patients. The mechanism of this diurnal variation was investigated in a further 5 asthmatic children (10.8 years ±1.6). Morning and night steady-state plasma theophylline concentrations during a continuous intravenous infusion of aminophylline were not different (14.9±5.3 mg/l vs. 15.6±5.9 mg/l), demonstrating that there was no diurnal variation in the plasma clearance of theophylline. The diurnal variation in predose concentrations with Neulin-SR250 was confirmed with the morning concentrations again being 2.6 fold greater than those in the evening. However, bioavailability was not significantly different for day (09.00–21.00) and night (21.00–09.00) dosing intervals after doses 6 and 7 respectively of Nuelin-SR250. The plasma concentration versus time profiles suggested that the diurnal variation in predose concentrations was due to slower absorption of the evening dose.
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  • 21
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    European journal of clinical pharmacology 24 (1983), S. 509-515 
    ISSN: 1432-1041
    Keywords: cibenzoline ; pharmacokinetics ; bioavailability ; urinary excretion ; antiarrhythmic drug ; healthy volunteers
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The kinetics of cibenzoline (UP 339.01), a new antiarrhythmic drug, was studied after i.v. and oral administration to 5 healthy subjects. Cibenzoline levels in plasma and urine cibenzoline were measured by a GLC method. After i.v. administration, the total clearance was 826 ml · min−1. The fraction of cibenzoline excreted unchanged in the urine was 0.602 and it was correlated with the creatinine clearance. After i.v. and oral administration, the renal clearances were 499 ml · min−1 and 439 ml · min−1, and the half-lives were 4 h 01 min and 3 h 24 min, respectively. The differences were not significant. Availability by the oral route was 0.92, the maximum plasma concentration being observed at 1 h 36 min. The results were compared with those for other antiarrhythmic drugs.
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    European journal of clinical pharmacology 25 (1983), S. 281-283 
    ISSN: 1432-1041
    Keywords: dyphylline ; pharmacokinetics ; bioavailability ; drug levels
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The pharmacokinetics and bioavailability of 3 oral dyphylline preparations, solution (S), regular (R) and sustained release (SR), were studied in 8 healthy subjects (mean age 25 years). A single dose of each preparation, 20 mg·kg−1, was given at one week intervals and multiple serum samples obtained over 24 h. Drug levels were measured by high performance liquid chromatography. No adverse effects were found. The dyphylline half-life for the solution was 2.16±0.18 h and for the tablet 2.59±0.56 h. The mean clearance rate for S was 13.6±1.7 h−1 and volume of distribution 43.0±3.91. Peak concentration (Cmax, µg·ml−1), time of peak (Tmax, h), area under the curve (AUC, µg·ml−1·h) and relative bioavailability (RB, %), were determined for three preparations: The data confirm the short half-life of dyphylline, demonstrate a lack of toxicity for the 20 mg·kg−1 dose and establish bioequivalence for the products studied.
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  • 23
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    European journal of clinical pharmacology 25 (1983), S. 357-359 
    ISSN: 1432-1041
    Keywords: pindolol ; bioavailability ; fluorimetric assay ; GLC-ECD assay
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The absolute oral bioavailability of pindolol has been estimated by two analytical methods, fluorimetry and GLC-ECD. The study was carried out in six healthy subjects who received either i.v. or oral pindolol in random order. The results obtained by both methods were similar and confirm the high bioavailability (about 75%) of pindolol. The present findings are compared with previous publications and emphasize the importance of undertaking bioavailability studies in the same subjects.
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  • 24
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    European journal of clinical pharmacology 24 (1983), S. 21-30 
    ISSN: 1432-1041
    Keywords: clonidine ; bioavailability ; blood pressure ; elimination half-life ; pharmacokinetics ; plasma catecholamines ; rebound phenomenon
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Using considerably improved analytical methods, the kinetics and effects of clonidine were observed in healthy volunteers over periods of time more than 3 times longer than those previously reported. The high sensitivity and small work load of the newly developed method permitted the performance of low-dose and multipledose trials. 1. The complete bioavailability of clonidine and its elimination half-life (20 to 25.5 h) remained constant after single and multiple doses. 2. Approximately 62% of a given dose was excreted unchanged in the urine, independent of the quantity administered (0.075, 0.15, 0.2, 0.25 or 0.3 mg), the drug formulation (solution, tablet, Perlonget) or of the mode of administration (i.v., p.o.; single or multiple doses). 3. As the pharmacokinetics of the drug were affected by entero-hepatic circulation, it cannot be described by a conventional, open one or two compartment model. 4. The time courses of the plasma clonidine concentration and its drug effects ran asynchronously. 5. On cessation of chronic clonidine administration, blood pressure and plasma catecholamine levels increased to pretreatment levels without exhibiting any “overshoot” reaction.
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  • 25
    ISSN: 1432-1041
    Keywords: theophylline ; smoking ; sustained release formulation ; dosage forms ; multidose pharmacokinetics ; bioavailability ; circadian variation in kinetics
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The pharmacokinetics and bioavailability of theophylline following 10 days of multiple doses of a plain uncoated (640 mg, q.i.d.) and a sustained-release tablet formulation (600 mg, b.i.d.) were related to habitual smoking in 11 healthy adult male volunteers, who had previously taken part in a single-dose study of an intravenous preparation of theophylline and of the same oral dosage form. There were significant differences (p〈0.05 to 0.01) in the steady-state mean and minimum theophylline concentration and AUC between the groups (6 smokers versus 5 nonsmokers), but not between other variables. A difference (p〈0.05) in peak time was also found between the dosage forms. The mean elimination t1/2 was significantly (p〈0.05) shorter in smokers than in nonsmokers. The intersubject variability in plasma theophylline concentration observed on the final trial day in the smoking group was larger and diverged more from simulation curves generated from the mean pharmacokinetic parameters of the single-dose study of the same formulations as compared to that of the nonsmoking group. There was no significant difference between the two groups in the mean accumulation ratio and absolute bioavailability of the two dosage forms. The mean morning (7 a.m.) trough theophylline concentrations after both formulations were significantly (p〈0.05 to 0.01) greater than the evening (7 p.m.) values within the same group. The average number of reported side-effects was significantly (p〈0.001) greater during the earlier period (Days 1 to 3) than the later period of the trial. A trend was observed suggesting that the incidence of side-effects was less in smokers than in nonsmokers. The results indicate that smoking is a determinant not only of enhanced elimination of theophylline but that it also produces more variability in the plasma level, irrespective of the dosage form administered or the dosing scheme employed. There may be circadian variation in theophylline kinetics.
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  • 26
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    European journal of clinical pharmacology 24 (1983), S. 415-419 
    ISSN: 1432-1041
    Keywords: prednisolone ; bioavailability ; non-linear pharmacokinetics ; protein binding
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The pharmacokinetics of prednisolone after oral and intravenous administration of 10 and 20 mg have been studied. Serum protein binding of prednisolone was also measured after the i.v. injections. The bioavailability after oral administration was 84.5% after 10 mg and 77.6% after 20 mg (p〉0.05). Dose dependent pharmacokinetics were found, the VDss and Clt being significantly larger (p〈0.01) after 20 mg i.v. than after 10 mg i.v. The protein binding of prednisolone in all subjects was non-linear, and is the most likely cause of the dose dependent pharmacokinetics, as there was no dose dependent variation in elimination half-time.
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  • 27
    ISSN: 1432-1041
    Keywords: ranitidine ; duodenal ulceration ; pharmacokinetics ; non-responders ; therapeutic response ; bioavailability
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The pharmacokinetics of orally administered ranitidine were studied in 17 male patients with chronic duodenal ulceration. The patients were divided into 2 groups, 10 responders and 7 nonresponders, on the basis of their endoscopic response to ranitidine treatment. The 10 responders were studied both after a single 150 mg dose (SD) and after multiple dosing (MD) with ranitidine 150 mg twice daily for 4 weeks. The area under the curve (AUC) and maximum concentration (Cmax) were significantly higher (p〈0.01 andp〈0.05, respectively) after MD than after SD, but the half-life (t1/2) and minimum concentration (Cmin) 12 h postdosing did not differ. The non-responders were studied after MD only and their pharmacokinetic characteristics were compared with those of responders. No differences between the 2 groups were found. However, 2 non-responders had particularly low plasma ranitidine levels and high acid output. Such patients may need larger doses of ranitidine for adequate suppression of gastric acid. Five patients (4 responders and 1 non-responder) received ranitidine 20 mg i.v. The drug followed a two-compartment model, with mean values for t1/2β, volume of distribution steady-state and total plasma clearance of 80 min, 701 and 680 ml/min, respectively. The oral bioavailability of ranitidine in these 5 patients showed wide variation (27–76%; mean 51%).
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    European journal of clinical pharmacology 24 (1983), S. 761-767 
    ISSN: 1432-1041
    Keywords: theophylline ; bioavailability ; sustained release tablet ; pharmacokinetics ; Theograd-250
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The bioavailability of theophylline after oral administration of a new sustained release tablet Theograd®-250 mg was studied in 7 healthy volunteers, under fasting and non-fasting conditions. Whilst fasting the bioavailability was moderate at 64±22% (mean±SD), whereas in the non-fasting state the relatively high bioavailability of 90±13% was found. The drug appeared to be significantly more slowly absorbed when a tablet was taken after a meal, than when it was ingested on an empty stomach. In the former case, the peak level was reached after 6.9±1.0 h, whereas in the fasting state the maximum serum concentration occurred 4.0±1.7 h after administration of the drug. Despite the slow absorption, the peak non-fasting level of 4.4±1.4 mg·l−1 was significantly higher than the 3.1±1.0 mg·l−1 observed in the fasting state. The profiles of the serum concentration-time curves showed that the concentration remained above 75% of Cmax for 8.7±1.3 h in the fasting and 9.0±1.1 h in the non-fasting state. It was concluded that to define the optimal dosage regime for sustained release oral dosage forms of theophylline, the influence of food on absorption from these preparations should be taken into account. Based on the present results, Theograd®-250 mg tablets have predictable absorption and a high (90%) bioavailability if taken after a meal.
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  • 29
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    European journal of clinical pharmacology 25 (1983), S. 69-72 
    ISSN: 1432-1041
    Keywords: levodopa ; intestinal absorption ; small intestine ; bioavailability ; benserazide ; presystemic clearance
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary In four healthy subjects the intestinal absorption of levodopa (l-dopa) was investigated by measuring the plasma concentration of the amino acid following the administration of l-dopa at three different sites in the small intestine. In order to minimize presystemic clearance of l-dopa, the subjects were pretreated with the peripheral decarboxylase inhibitor benserazide 3×50 mg every 8 h on the previous day and 1×50 mg 2 h prior to administration of the l-dopa. L-dopa 100 mg dissolved in 0.05 N HCl and 50 mg benserazide dissolved in 0.05 N HCl were coadministered. Under these conditions no difference in tmax, cmax or AUC of l-dopa was observed between administration of the drug into the proximal or the distal part of duodenum, or into the upper part of jejunum. The results indicate that in healthy subjects, during inhibition of peripheral decarboxylase, the rate and extent of l-dopa absorption does not differ at any site in the upper small intestine.
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  • 30
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    European journal of clinical pharmacology 36 (1989), S. 383-388 
    ISSN: 1432-1041
    Keywords: naproxen ; sustained-release formulation ; pharmacokinetics ; bioavailability ; efficacy ; tolerability
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    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.
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  • 31
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    European journal of clinical pharmacology 37 (1989), S. 313-316 
    ISSN: 1432-1041
    Keywords: diprafenone ; pharmacokinetics ; bioavailability ; first-pass metabolism ; healthy volunteers
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    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.
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    European journal of clinical pharmacology 37 (1989), S. 85-90 
    ISSN: 1432-1041
    Keywords: theophylline ; sustained-release formulation ; bioavailability ; fatty food ; dumping effect ; pharmacokinetics
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    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.
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  • 33
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    Journal of pharmacokinetics and pharmacodynamics 11 (1983), S. 561-576 
    ISSN: 1573-8744
    Keywords: methylprednisolone ; bioavailability ; pharmacokinetics ; oral and parenteral administration
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    Topics: Chemistry and Pharmacology
    Notes: Abstract This study was conducted to evaluate the influence of route of administration upon the bioavailability and pharmacokinetics of methylprednisolone sodium succinate. Fourteen healthy adult male volunteers received 40 mg doses of methylprednisolone as the following treatments after an overnight fast in a 4-way crossover design: (a) as a 1 ml i.v. bolus;(b) as a 1 ml i.m. injection;(c) administered as an oral solution;and (d) as 5×8 mg oral tablets. Both the ester and free methylprednisolone were determined in plasma and urine. Study results indicate that the ester is rapidly and extensively converted to free methylprednisolone after all routes. The extent of methylprednisolone absorption was equivalent after i.v. and i.m. administration. Both orally administered treatments resulted in a lower extent of absorption attributed to a first-pass effect. Although a slightly lower extent of absorption was demonstrated following the oral administration of the methylprednisolone sodium succinate solution relative to the methylprednisolone oral tablets, this average difference of 9% would probably be of minimal therapeutic importance.
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  • 34
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    Journal of pharmacokinetics and pharmacodynamics 11 (1983), S. 205-214 
    ISSN: 1573-8744
    Keywords: bioavailability ; clearance ; V area ; V ss
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    Topics: Chemistry and Pharmacology
    Notes: Abstract The limitations of using estimates of extent of bioavailability (F) based on the assumption that either clearance (CL) or Varea remain, constant are discussed in relation to the situation where CL changes between doses. When estimates of F assume CL to remain constant, the entent of the error is the same for all drugs where the percentage change in CL is the same. Assuming Varea to remain constant, the error in F will vary between drugs for similar percentage changes in CL and is related to the extent to which the kinetics of the disposition process deviate from a one compartment body model. A noncompartmental method is described where, provided the reference dose is given intravenously, F can be estimated based on the assumption that Vss remains constant between doses. This method is more accurate than those based on the assumption that either CL or Varea remain, constant when CL changes between doses, but is subject to error when the terminal loglinear slope of Cp vs. time better reflects the process of absorption rather than elimination.
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  • 35
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    Journal of pharmacokinetics and pharmacodynamics 11 (1983), S. 529-545 
    ISSN: 1573-8744
    Keywords: bioavailability ; nitrofurantoin ; capacity-limited elimination
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    Topics: Chemistry and Pharmacology
    Notes: Abstract The influence of route of administration on the absolute bioavailability and GI tract absorption of nitrofurantoin was investigated in rabbits. The disposition of nitrofurantoin was described by a one-compartment model with simultaneous first-order and Michaelis-Menten type elimination kinetics, and bioavailability was estimated by nonlinear assessment. The plasma levels following oral administration were significantly lower than those after intravenous administration, and absolute Fvalues for oral administration were approximately 0.3. However, Fvalues following intraduodenal administration and portal vein infusion were nearly unity, and it was concluded that the reduction of bioavailability following oral administration could not be attributed to metabolism by intestinal microflora or to the hepatic first-pass effect. Thus, reduction of Fvalues following oral administration is probably due to gastric degradation of the drug. The effects of factors influencing bioavailability, such as water volume taken with the drug, change of gastric emptying rate and effect of particle size, were also investigated. Increase of volume of water administered tended to improve the bioavailability, and a particle size dependency was also observed.
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  • 36
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    Hydrobiologia 188-189 (1989), S. 149-153 
    ISSN: 1573-5117
    Keywords: bacterial assays ; toxicity assessment ; microtox test ; oxygen consumption assay ; glucose mineralization assay ; bioavailability
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    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.
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  • 37
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    Hydrobiologia 176-177 (1989), S. 491-495 
    ISSN: 1573-5117
    Keywords: metal uptake ; dialysis with receiving resins ; bioavailability ; urban stormwaters
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    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.
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  • 38
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    Hydrobiologia 188-189 (1989), S. 487-496 
    ISSN: 1573-5117
    Keywords: heavy metals ; sediment ; speciation ; bioavailability ; tubificid worms
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    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.
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  • 39
    ISSN: 1573-5117
    Keywords: bioavailability ; bioaccumulation ; hydrophobicity ; fish ; chlorobenzenes
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    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.
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  • 40
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    Plant foods for human nutrition 39 (1989), S. 3-11 
    ISSN: 1573-9104
    Keywords: protein quality ; amino acids ; digestibility ; bioavailability ; rats ; in vitro enzyme assays
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    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.
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    Plant foods for human nutrition 39 (1989), S. 85-91 
    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.
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  • 42
    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.
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  • 43
    ISSN: 1573-904X
    Keywords: bioavailability ; scintigraphy ; gastrointestinal transit ; controlled release ; phenylpropanolamine ; hydroxypropylmethylcellulose
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    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.
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  • 44
    ISSN: 1573-904X
    Keywords: insulin ; collagen ; injection ; subcutaneous injection ; bioavailability
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    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.
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  • 45
    Electronic Resource
    Electronic Resource
    Springer
    Pharmaceutical research 6 (1989), S. 817-821 
    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
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