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  • bioavailability  (7)
  • Springer  (7)
  • Periodicals Archive Online (PAO)
  • 1980-1984  (7)
  • 1983  (7)
Collection
Publisher
  • Springer  (7)
  • Periodicals Archive Online (PAO)
Years
  • 1980-1984  (7)
Year
  • 1
    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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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    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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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    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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  • 4
    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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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    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
    Source: Springer Online Journal Archives 1860-2000
    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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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    European journal of clinical pharmacology 25 (1983), S. 357-359 
    ISSN: 1432-1041
    Keywords: pindolol ; bioavailability ; fluorimetric assay ; GLC-ECD assay
    Source: Springer Online Journal Archives 1860-2000
    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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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    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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