Effect of indinavir on the pharmacokinetics of rifampicin in HIV-infected patients

Indinavir, an antiretroviral agent, has an influence on the pharmacokinetics of other drugs by acting as an inhibitor of cytochrome P450-mediated drug metabolism. The incidence of tuberculosis has increased dramatically in the past decade because of an epidemic of HIV infection. Rifampicin is still one of the most valuable drugs for the standard treatment of tuberculosis. The objective of this study was to investigate the effects of indinavir on the pharmacokinetics of rifampicin in man. Our study was conducted in eleven HIV-infected patients. All patients received a 600-mg single dose of oral rifampicin on day 1 and 15- and 800-mg oral indinavir three times a day from day 2 to day 15. Rifampicin pharmacokinetic studies were carried out on day 1 and day 15. The results showed that rifampicin concentrations were higher when it was administered with indinavir than when it was administered alone. With concomitant indinavir medication, the mean AUC0-24 of rifampicin was increased by 73%. Therefore, we conclude that indinavir has an inhibitory effect on the metabolism of rifampicin.