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  • 1
    ISSN: 1432-1041
    Keywords: tolbutamide ; antipyrine ; selective inhibition ; metabolite formation ; pharmacokinetics ; drug interaction ; sulphaphenazole ; cimetidine ; primaquine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The effects of sulphaphenazole, cimetidine and primaquine on the disposition of antipyrine and tolbutamide in healthy volunteers have been investigated. The model substrates were administered simultaneously in order more clearly to define any selective effects of the potential inhibitors. Sulphaphenazole produced a significant increase in the half-life of tolbutamide (7.10 to 21.50 h) and a correponding decrease in its clearance (0.260 to 0.084 ml·min−1·kg−1). Clearance to hydroxytolbutamide (OHTOL) and carboxytolbutamide (COOHTOL) was also significantly decreased. In contrast, sulphaphenazole had no effect on the disposition of antipyrine. Administration of cimetidine did not significantly alter the disposition of either model drug. However, a 1.6-times higher dose of cimetidine did increase the half lives both of tolbutamide and antipyrine (6.21 to 9.04 h and 14.2 to 19.2 h, respectively) and decrease their clearance (0.226 to 0.148 and 0.50 to 0.31 ml·min−1 kg−1, respectively). Clearance to OHTOL and hydroxymethylantipyrine (HMA) was reduced. A single dose of primaquine had no demonstrable effect on tolbutamide disposition whereas the half-life of antipyrine was increased (12.1 to 15.0 h) and its clearance decreased (0.63 to 0.38 ml·min−1·kg−1). The partial clearance to HMA, 4-hydroxyantipyrine (OHA) and norantipyrine (NORA) was also significantly reduced. The two main inferences are first, that tolbutamide and antipyrine are metabolished by different forms of cytochrome P-450, and second that a battery of model substrates is needed to investigate the inhibitory effects of a drug in man.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-1041
    Keywords: mefloquine ; falciparum malaria ; Thai subjects ; pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary We have studied the kinetics of a single oral dose of mefloquine (750 mg) in 12 Thai patients with falciparum malaria and have compared the results with those of a previous study in 12 healthy Thai volunteers [6]. All the patients responded to treatment with a mean parasite clearance time of 66.6 h and a mean fever clearance time of 54.1 h. There was no significant difference in peak plasma concentration, time to peak, area under the curve or apparent volume of distribution between patients and controls. However, the terminal half-life (t1/2) and mean residence time (MRT) were shorter in the patients (12.2 vs 16.7 days for t1/2 and 15.5 vs 21.4 days for MRT). We conclude that there are changes in the disposition of mefloquine related to malaria, although the exact basis of the changes is not clear.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    European journal of clinical pharmacology 48 (1995), S. 65-69 
    ISSN: 1432-1041
    Keywords: Paracetamol ; Malaria ; pharmacokinetics ; phase II conjugation ; glucuronidation ; sulphation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Abstract Investigations in animals have suggested that conjugation of paracetamol may be reduced in malaria. We have measured plasma concentrations and the urinary excretion of paracetamol and its phase II metabolites in eight Thai patients during uncomplicated falciparum malaria and in convalescence, following a 1000 mg single oral dose. The apparent oral clearance (Malaria, 3.6; Convalescence, 3.9; ml·min−1·kg−1), the elimination half-life (Malaria, 3.8; Convalescence, 3.7 h) and apparent volume of distribution (Malaria, 1.2; Convalescence, 1.2; l·kg−1) of paracetamol were similar during malaria and convalescence. In addition, the urinary excretion of paracetamol and its major phase II metabolites and their formation clearances from paracetamol were not significantly different between the two study phases. These data show that clinical malaria infection has no effect on the conjugation of paracetamol in man.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    European journal of clinical pharmacology 40 (1991), S. 631-633 
    ISSN: 1432-1041
    Keywords: Mefloquine ; ampicillin ; Thai subjects ; pharmacokinetics ; enterohepatic recycling ; drug interaction ; adverse effects
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The kinetics of a single oral dose of mefloquine given either alone or with ampicillin has been studied in 8 healthy Thai male volunteers. There was a significantly higher maximum whole blood mefloquine concentration after coadministration with ampicillin (1648 vs 1228 ng·ml−1), as well as a significantly reduced terminal half life (15.3 vs 17.7 days), mean residence time (20.1 vs 23.4 days) and volume of distribution at steady state (14.1 vs 19.4 l·kg−1). Although there was no significant change in the AUC from zero time to infinity, the AUC from zero time to 5 days was significantly increased by ampicillin (4.86 vs 3.27 μg·ml−1 day). These changes in mefloquine disposition after antibiotic treatment may be due both to an increase in fractional bioavailability and a reduction in the enterohepatic recycling of mefloquine.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    European journal of clinical pharmacology 44 (1993), S. 203-204 
    ISSN: 1432-1041
    Keywords: Chlormethiazole ; hepatic monooxygenase activity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Chlormethiazole is a strong inhibitor of cytochrome P-450-dependent monooxygenases in isolated human liver microsomes. To assess its effect in vivo, we measured the pharmacokinetic parameters of antipyrine (1.2 g orally) and tolbutamide (0.5 g i. v.) before and after administration of chlormethiazole 314 mg b. d. for 2 days to 8 healthy volunteers. The elimination of neither substance was affected, indicating that chlormethiazole did not inhibit in vivo the cytochrome P-450 isozymes responsible for the elimination of antipyrine and tolbutamide.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    European journal of clinical pharmacology 15 (1979), S. 193-197 
    ISSN: 1432-1041
    Keywords: norethisterone ; rifampicin ; enzyme induction ; antipyrine ; 6 beta-hydroxycortisol ; gamma-glutamyltranspeptidase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The pharmacokinetics of norethisterone have been studied in 8 women during and one month after treatment with rifampicin (450–600 mg/day). Rifampicin caused a significant reduction in the A. U. C. of a single dose of 1 mg norethisterone from 37.8±13.1 to 21.9±5.9 ng/ml X h (p〈0.01). The plasma norethisterone half life (β-phase) was also reduced from 6.2±1.7 to 3.2±1.0 h (p〈0.0025). In one additional woman on long term oral contraceptive therapy the 12 hour plasma norethisterone concentration was reduced by rifampicin from 12.3 ng/ml to 2.3 ng/ml. Rifampicin caused a significant increase in antipyrine clearance, 6β-hydroxycortisol excretion and plasma gamma-glutamyltranspeptidase activity but there were no significant correlations between changes in these indices of liver microsomal enzyme induction. There was a significant correlation between the percentage increase in antipyrine clearance and the percentage decrease in norethisterone A. U. C. during rifampicin. The changes in norethisterone pharmacokinetics during rifampicin therapy are compatible with the known enzyme inducing effect of rifampicin.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1432-1041
    Keywords: mefloquine ; mefloquine/sulphadoxine/pyrimethamine ; Thai subjects ; pharmacokinetics ; drug interactions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The kinetics of mefloquine were studied in 12 healthy Thai male and 12 healthy Thai female volunteers. Mefloquine (MQ) was administered either alone (750 mg orally) or in combination (MSP) with sulphadoxine (1.5 g) and pyrimethamine (75 mg) to each of 6 male and 6 female subjects. Plasma concentrations of MQ were measured by HPLC at intervals for 42 days. There was considerable interindividual variability in the pharmacokinetic parameters; for example in the male subjects receiving MQ alone peak concentrations ranged between 638 and 2494 ng·ml−1 with a mean concentration of 1442 ng·ml−1. Compared to previously published data on MQ concentrations in Caucasian male subjects, the present study indicates that higher concentrations are achieved in Thai subjects. The only significant difference in kinetic parameters between male and female subjects receiving MQ alone was in the mean residence time (MRT) which was greater in females. However, an analysis of pharmacokinetic parameters following administration of the combination preparation showed that the time to peak (tmax) was significantly reduced in females receiving MSP compared to the corresponding females given MQ alone and males given MSP. When data obtained from all subjects (male and female) receiving either MQ alone or MSP were combined, both MRT and half-life were significantly greater in subjects given MSP. There is therefore some evidence that therapeutic concentrations of MQ are maintained for a longer period of time following MSP administration.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    European journal of clinical pharmacology 43 (1992), S. 567-569 
    ISSN: 1432-1041
    Keywords: Mefloquine ; Tetracycline ; Thai subjects ; Thai subjects ; drug interaction ; pharmacokinetics ; adverse effects
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The kinetics of a single oral dose of mefloquine given either alone or with tetracycline has been studied in 20 healthy Thai male volunteers. There was a significantly higher maximum whole blood mefloquine concentration after coadministration with tetracycline (1600 vs 1160 ng · ml−1), as well as a significantly reduced terminal half-life (14.4 vs 19.3 days), mean residence time (11.9 vs 16.0 days) and volume of distribution at steady state (13.3 vs 19.91 · kg−1). Although there was no significant change in the AUC from zero time to infinity, the AUC from zero time to 7 days was significantly increased by tetracycline (6.18 vs 4.76 μg · ml−1 · day). The changes in mefloquine disposition after tetracycline treatment are probably due to a reduction in enterohepatic recycling. The initial increase in mefloquine AUC without an apparent increase in side-effects suggests that this combination may have a place in the treatment of multi-drug resistant falciparum malaria.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    European journal of clinical pharmacology 32 (1987), S. 203-205 
    ISSN: 1432-1041
    Keywords: paracetamol ; primaquine ; drug interaction ; metabolite formation ; pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The kinetics of paracetamol and the formation of metabolites were evaluated in 6 healthy volunteers before and during concomitant administration of a single dose (45 mg) of primaquine. There was no effect of the antimalarial drug on either conjugation (to paracetamol glucuronide and paracetamol sulphate) or oxidation (as judged by the presence of paracetamol cysteine and paracetamol mercapturate) pathways. Although primaquine inhibits certain oxidative metabolism (e.g. of antipyrine) it has no effect, in therapeutic doses, on paracetamol metabolism.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    European journal of clinical pharmacology 42 (1992), S. 559-560 
    ISSN: 1432-1041
    Keywords: Mefloquine ; Thai subjects ; pharmacokinetics ; Primaquine ; drug interaction ; adverse effects
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Type of Medium: Electronic Resource
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