a placebo-controlled study, 10 healthy subjects were given oral triazolam 0.5 mg before and after rifampicin 600 mg daily for 5 days. Rifampicin reduced the triazolam AUC by 95% and decreased its maximum plasma levels by 88%, when compared with placebo. The elimination half- life was reduced from 2.8 hours to 1.3 hours. Pharmacodynamic tests (drowsiness, sway, Maddox wing, etc.) showed that rifampicin abolished the effects of triazolam. a) Why is the AUC of triazolam reduced in the presence of rifampicin? b) Given the above scenario, if you were to accommodate this situation by dosage adjustment strategies, in the presence rifampicin what dose of triazolam would you have recommended, keeping dosage interval the same as when there was no rifampicin? answer part b
In a placebo-controlled study, 10 healthy subjects were given oral triazolam 0.5 mg before and
after rifampicin 600 mg daily for 5 days. Rifampicin reduced the triazolam AUC by 95% and
decreased its maximum plasma levels by 88%, when compared with placebo. The elimination half-
life was reduced from 2.8 hours to 1.3 hours. Pharmacodynamic tests (drowsiness, sway, Maddox
wing, etc.) showed that rifampicin abolished the effects of triazolam.
a) Why is the AUC of triazolam reduced in the presence of rifampicin?
b) Given the above scenario, if you were to accommodate this situation by dosage adjustment
strategies, in the presence rifampicin what dose of triazolam would you have recommended,
keeping dosage interval the same as when there was no rifampicin?
answer part b
A. Rifampicin induces the activity of drug-metabolizing enzymes, including cytochrome P450 3A4 (CYP3A4), which is responsible for the metabolism of triazolam. The induction of CYP3A4 by rifampicin leads to increased metabolism of triazolam, resulting in decreased plasma levels and reduced AUC
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