The effect of enzyme induction by antipyrine, phenobarbitone and rifampicin on the time-course of urinary 6β-hydroxycortisol (6β-OHC) excretion was investigated in healthy volunteers. The drugs were given chronically for either seven or 14 days.
Significant increases in 6β-OHC excretion were observed after 4 days administration of antipyrine (1.2 g), 13 days administration of phenobarbitone (100 mg), and only 2 days administration of rifampicin (0.6 or 1.2 g). During 14 days rifampicin administration (1.2 g) 6β-OHC excretion, for individual subjects, reached a maximum on Days 11–14 when excretion was significantly greater than on day 7. On stopping rifampicin, in a 7-day study, excretion decreased over the next six days, but still remained significantly elevated compared to the original control values.
These studies show that measurement of urinary 6β-hydroxycortisol provides a simple non-invasive method with which to monitor the time-course of enzyme induction by drugs in man. However, the method cannot be used to predict clinically important drug interactions until the cytochrome P-450 enzyme responsible for cortisol 6β-hydroxylation has been fully characterized.
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Dedication. Causes of the variability of drug response has been a continuing preoccupation of pharmacologists for many years. Over the last twelve years, the authors of this paper have collaborated in many studies on various facets of this subject, most concerned with the problems of microsomal enzyme induction.
Edgar Ohnhaus, the first author, died in January 1988. This paper aims to put in context important new data with those produced in other studies and which the authors have published together. It is presented as a scientific tribute to a skilled and tenacious clinical pharmacologist who is sadly missed
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Ohnhaus, E.E., Breckenridge, A.M. & Park, B.K. Urinary excretion of 6β-hydroxycortisol and the time course measurement of enzyme induction in man. Eur J Clin Pharmacol 36, 39–46 (1989). https://doi.org/10.1007/BF00561021
- enzyme induction
- cytochrome P 450
- urinary excretion
- healthy volunteers