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  • 1
    Electronic Resource
    Electronic Resource
    Selective inhibition of drug oxidation after simultaneous administration of two probe drugs, antipyrine and tolbutamide (1988)
    Springer
    European journal of clinical pharmacology 34 (1988), S. 157-163 
    Details
    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
    URL: http://dx.doi.org/10.1007/BF00614553
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  • 2
    Electronic Resource
    Electronic Resource
    Measurement of urinary 6-β-hydroxycortisol excretion as an in vivo parameter in the clinical assessment of the microsomal enzyme-inducing capacity of antipyrine, phenobarbitone and rifampicin (1979)
    Springer
    European journal of clinical pharmacology 15 (1979), S. 139-145 
    Details
    ISSN: 1432-1041
    Keywords: enzyme induction ; 6-beta-hydroxycortisol ; antipyrine ; phenobarbitone ; rifampicine ; urinary excretion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary To assess the rate of drug metabolism in man, four different in vivo measurements of microsomal enzyme activity were compared before and after the administration of three drugs known to be enzyme inducers in man: antipyrine, phenobarbitone and rifampicin. 27 healthy volunteers, divided into four different groups, were given antipyrine 1000 mg or 1200 mg, phenobarbitone 100 mg and rifampicin 600 mg or 1200 mg daily for 14 days. Before and after each drug, estimates were made of total body clearance of antipyrine, γ-glutamyl-transpeptidase in plasma and d-glucaric acid, 6-β-hydroxycortisol and 17-hydroxycorticosteroid urinary excretion in 24 h, as parameters of hepatic microsomal enzyme activity. Following treatment with antipyrine, phenobarbitone or rifampicin 600 mg daily, the total body clearance of antipyrine increased by 44–60%, and after rifampicin 1200 mg there was an increase up to 125%. d-Glucaric acid excretion in urine showed a tendency to increase to the same extent in every group investigated, and γ-glutamyl-transpeptidase increased similarly following antipyrine and phenobarbitone, although it remained unchanged following rifampicin administration. Urinary excretion of 6-β-hydroxycortisol, corrected by the 17-hydroxycorticosteroids representing the percentage proportion of 6-β-hydroxycortisol of the total amount of 17-hydroxycorticosteroids excreted, increased from 4.6–5.2% up to 9.5–28.3% depending upon the drug given. Comparing all in vivo parameters of hepatic microsomal enzyme activity by means of linear regression, a significant correlation was found between total body clearance of antipyrine and urinary excretion of 6-β-hydroxycortisol, while none of the other parameters showed any significant correlation. In addition, a better seperation of the enzyme-inducing capacity of different drugs was seen using 6-β-hydroxycortisol as a parameter of microsomal enzyme activity. Therefore, measurement of 6-β-hydroxycortisol corrected by the 17-hydroxycorticosteroid excretion, combined with estimation of the total body clearance of antipyrine, gives a valuable index, suitable for use in further studies of induction in man.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00609878
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Enzyme-inducing drug combinations and their effects on liver microsomal enzyme activity in man (1983)
    Springer
    European journal of clinical pharmacology 24 (1983), S. 247-250 
    Details
    ISSN: 1432-1041
    Keywords: antipyrine ; phenobarbitone ; rifampicin ; drug combinations ; enzyme induction ; antipyrine clearance ; 6-β-hydroxycortisol
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The effect of 2 different drug combinations on liver microsomal activity was investigated in healthy volunteers by administering antipyrine 1200 mg and phenobarbitone 100 mg, or the same dose of antipyrine with rifampicin 600 mg daily for 14 days. The effect of rifampicin 1200 mg given for only 8 days was also studied. Before and after each drug regimen, estimates were made of the total body clearance of antipyrine, γ-glutamyl-transferase (γ-GT) and urinary excretion of 6-β-hydroxycortisol as in vivo parameters of liver microsomal enzyme activity. Following combined antipyrine and phenobarbitone administration, the antipyrine clearance was increased by 80%, after antipyrine with rifampicin by 128%, and after rifampicin alone by 104%. 6-β-hydroxycortisol, corrected for 17-hydroxycorticosteroids, increased from 2.6% to 8% following antipyrine plus phenobarbitone, from 4.4% to 27.9% following antipyrine plus rifampicin, and from 5.4% to 29.7% after rifampicin given alone. Based on previous studies, antipyrine given with phenobarbitone produced slightly more induction than phenobarbitone given alone. Following antipyrine 1200 mg with rifampicin 600 mg for 14 days a significantly greater increase in antipyrine clearance and 6-β-hydroxycortisol excretion was observed than when either drug was given alone.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00613826
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    Paper (German National Licenses)
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