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  • pharmacokinetics  (578)
  • Springer  (578)
  • 1985-1989  (578)
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  • 11
    Electronic Resource
    Electronic Resource
    Springer
    European journal of clinical pharmacology 32 (1987), S. 411-418 
    ISSN: 1432-1041
    Keywords: 5-fluorouracil ; colorectal carcinoma ; pharmacokinetics ; product-inhibition ; blood clearance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The nonlinear disposition kinetics of 5-fluorouracil (5-FU) were investigated in 6 patients with colorectal carcinoma. Each patient randomly received two single, intravenous doses of 5-FU (7.5 and 15 mg/kg) on separate days. Venous blood and urine samples were collected just prior to and for 5 h after drug administration. In addition to the kinetic studies, the in vitro whole blood/plasma concentration ratio and stability of 5-FU at 37°C were determined in whole blood from normal volunteers and from 5 patients with colorectal carcinoma. A disproportionate increase in area under the curve and corresponding decrease in total body clearance with increasing dose was observed suggesting dose-dependent behavior of 5-FU. Doubling the dose was accompanied by a 36% decrease in nonrenal clearance but no apparent change in renal clearance. Therefore, the mechanism for dose-dependent elimination appears to be primarily associated with nonrenal processes. The mean 5-FU half-life following the high dose was nearly twice as long as that observed for the low dose (12.3 versus 6.2 min). The log-linear decline in plasma concentrations and increase in half-life with dose suggest the potential role of product-inhibition as an explanation for the observed nonlinearity in 5-FU elimination. The present study demonstrates that 5-FU degrades when incubated in whole blood. This most likely reflects metabolism in red blood cells or other blood-formed elements since 5-FU was stable in plasma. Although degradation in whole blood occurs, the estimated whole blood clearance does not contribute significantly to the observed total body clearance value. These findings suggest the possibility of pulmonary clearance of 5-FU.
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  • 12
    Electronic Resource
    Electronic Resource
    Springer
    European journal of clinical pharmacology 32 (1987), S. 431-432 
    ISSN: 1432-1041
    Keywords: theophylline ; fluoroquinolones ; drug interaction ; pharmacokinetics ; ofloxacin ; norfloxacin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Pretreatment for 3 days with oral ofloxacin or norfloxacin had no significant effect on the disposition of a single i.v. dose the theophylline in healthy volunteers.
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  • 13
    ISSN: 1432-1041
    Keywords: growth hormone releasing factor ; radio-immunoassay ; pharmacokinetics ; variance model
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Three ranges of doses of growth hormone releasing factor (2.5–80 µg, 80–320 µg and 75–600 µg) were intravenously administered to healthy young volunteers in three double blind studies. Serum circulating GRF levels were determined by radioimmunoassay. Experimental concentration curves were fitted, using the extended least squares method, to a biexponential model for the structural model and power function for the variance model. The power variance model, compared to the constant variance model greatly reduced the coefficient of variation of the biexponential parameters. The power of the variance model was estimated to be 1.95. The distribution half-life was 6.6 min and the elimination half-life was 39.0 min (harmonic means). Total clearance was 0.12±0.01 µg/l/min. No difference between these parameters was found for the various doses. GRF kinetics was linear established in the range 10 to 600 µg which means that elimination was not altered by the increased doses.
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  • 14
    Electronic Resource
    Electronic Resource
    Springer
    European journal of clinical pharmacology 32 (1987), S. 563-568 
    ISSN: 1432-1041
    Keywords: nitrendipine ; pharmacokinetics ; hepatitis ; liver cirrhosis ; protein binding
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Twenty one patients with liver disease (cirrhosis 11, chronic hepatitis 5 and acute hepatitis 5) and 6 healthy volunteers were given a single i.v. dose of nitrendipine 5 mg. Afterwords nitrendipine 20 mg once daily were administered orally for seven days. With the intravenous injection a significant increase in the AUC and elimination half-life of nitrendipine was found in patients with cirrhosis as compared to the normal volunteers. After chronic oral dosing, the area under the plasma concentration-time curve, AUC (0–24), was 94.5 ng ml−1 h and the plasma clearance CL was 1380.6 ml/min in the healthy controls; in patients with cirrhosis the AUC (0–24) h was significantly greater at 309.4 ng ml−1 h and CL had fallen to 686.6 ml/min. Considerable accumulation of nitrendipine was also found in the patients with chronic hepatitis. Nitrendipine could not be detected in urine from any of the subjects. Blood pressure and heart rate were not significantly influenced by the treatment in the various groups investigated. Antipyrine clearance in the patients with cirrhosis was correlated with the nitrendipine plasma clearance. Thus, accumulation of nitrendipine has been demonstrated in the patients with cirrhosis and chronic hepatitis.
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  • 15
    Electronic Resource
    Electronic Resource
    Springer
    European journal of clinical pharmacology 32 (1987), S. 597-605 
    ISSN: 1432-1041
    Keywords: iloprost ; prostacyclin analogue ; pharmacokinetics ; pharmacodynamics ; radiolabeled study ; volunteers ; side-effects
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The plasma levels and excretion of tritium-labeled iloprost in healthy elderly male and female volunteers have been measured after i.v. infusion of 2 ng·kg−1·min−1 for 4 h and oral administration of 0.1 and 0.48 μg/kg. During infusion, a steady-state of labeled compounds in the plasma was not achieved. Total radioactivity declined from a mean of 408 pg equiv/ml in three phases, with half-lives of 24 min, 1.7 h and 5.0 h, respectively. A steady-state of unchanged iloprost was reached rapidly with a peak of 81 pg/ml. Plasma levels declined biphasically with half-lives of 6 min and 31 min. Total clearance was 24 ml· min−1·kg−1. Maximum concentrations of labeled substances after oral administration were 307 and 1,051 pg equiv/ml after 29 and 39 min respectively. The peak of unchanged iloprost (116 pg/ml) was observed 7.5 min after an oral dose of 0.48 μg/kg. Bioavailability was 16%. Iloprost was totally metabolized and the metabolities were mainly excreted in urine. The main biotransformation products in plasma and urine were tentatively identified by cochromatography as dinor-and tetranoriloprost and their glucuronides. ADP-induced platelet aggregation was reduce by 60% during the i.v. infusion and 15 min after oral administration of 0.48 μg/kg. Heart rate and blood pressure were virtually unaffected. Common side-effects were facial flush, headache and nausea.
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  • 16
    Electronic Resource
    Electronic Resource
    Springer
    European journal of clinical pharmacology 32 (1987), S. 625-629 
    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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  • 17
    Electronic Resource
    Electronic Resource
    Springer
    European journal of clinical pharmacology 33 (1987), S. 197-201 
    ISSN: 1432-1041
    Keywords: ceftazidime ; renal impairment ; plasmapheresis ; pharmacokinetics ; cephalosporins ; autoimmune disease
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The influence of plasmapheresis (PA) on the elimination kinetics of ceftazidime (Cef) has been investigated. A single dose of Cef was administered intravenously to 11 patients with autoimmune diseases and varying degrees of renal impairment (Group I CLCR〈50 ml/min, Group II CLCR〉50 ml/min). In Groups I and II the mean total clearance of Cef (CL) was 30 and 116 ml/min−1, respectively. The elimination half-life (t1\2β) and the volume of distribution (V) were significantly higher in Group I than in Group II (11.9 vs 2.0 h, 27.1 vs 18.5 l). PA had no influence on the plasma level-time profile of Cef. The amount of Cef recovered from separated plasma accounted for only 2 to 9% of the administered dose, being particularly low in patients with normal renal function (4.6%). Thus, since elimination of Cef via PA is negligible, dosage calculations should be based solely on renal function.
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  • 18
    Electronic Resource
    Electronic Resource
    Springer
    European journal of clinical pharmacology 33 (1987), S. 227-230 
    ISSN: 1432-1041
    Keywords: enoxacin ; theophylline ; drug interaction ; healthy volunteers ; adverse effects ; pharmacokinetics ; renal tubular excretion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The mechanism of the theophylline-enoxacin interaction has been studied in six healthy subjects. Theophylline 250 mg was administered p.o., twice daily for 11 days in a sustained release dosage form. On the 4th day of treatment, blood samples were taken every 2 h and urine was collected over 1 dose interval. From Days 5 to 11 coated tablets of enoxacin 400 mg b.i.d. were coadministered. On Day 11 blood and urine were collected as on Day 4. The mean plasma theophylline concentration rose from 4.4 to 15.1 mg/l, corresponding to a 73.6% reduction in total clearance. The urinary excretion of unchanged theophylline increased from 12.7 to 35.3%, whereas the production of metabolites was reduced (1-demethylation 81.4%; 3-demethylation 83.1%, 8-hydroxylation 74.6%). The results indicate that the theophylline-enoxacin interaction may be due to inhibition of the cytochrome P-450 isozymes responsible for theophylline metabolism. Unexpectedly, the renal clearance of theophylline metabolites was found to be drastically reduced when enoxacin was coadministered. This led to unchanged or even to elevated plasma levels of the metabolites. The mechanism of this interaction is still to be elucidated, but it may be due to competition for renal tubular secretion.
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  • 19
    ISSN: 1432-1041
    Keywords: iron deficiency anaemia ; sulphadimidine ; absorption ; pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The effect of iron deficiency anaemia and its treatment on the absorption of sulphadimidine has been investigated in adult patients. The absorption judged by total % of the dose excreted in urine and Cmax, tmax, AUC and Kabs in plasma, was not significantly different before and after iron therapy or correction of anaemia. However, sulphadimidine absorption by the anaemic patients was significantly greater than in normals.
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  • 20
    Electronic Resource
    Electronic Resource
    Springer
    European journal of clinical pharmacology 33 (1987), S. 315-318 
    ISSN: 1432-1041
    Keywords: propranolol ; pharmacodynamics ; pharmacokinetics ; beta-blockade ; sustained-release propranolol
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The duration and extent of cardiac beta-blockade and their relationship to propranolol pharmacokinetics were assessed in nine healthy volunteers. Each subject received 160 mg of regular propranolol (R), 160 mg of sustained-release propranolol (SR) and no drug (control), both as single doses and once daily for 7 days. After single doses and at steady-state, both products caused a decrease in exercise heart rate for at least 24 h, compared to control. The time course of effect was similar to the time course of serum propranolol concentration. The oral clearance of propranolol decreased from single doses to steady-state for both R and SR; however, the difference achieved statistical significance only for R. These changes were reflected in mean accumulation ratios (AUC steady-state 0–24 h/AUC single dose 0-infinity) of 1.49 and 1.68 for R and SR, respectively. The pharmacokinetic data are consistent with a decrease in intrinsic hepatic clearance of propranolol, leading to an increase in bioavailability at steady-state. Despite a two-fold difference in the bioavailability of R and SR, there was no difference in the area under the effect-time curve at steady-state.
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