Pharmacokinetic Evaluation of Emtricitabine in Combination With Other Nucleoside Antivirals in Healthy Volunteers

Emtricitabine is a potent nucleoside reverse transcriptase inhibitor approved as a once‐daily drug in combination with other antiretroviral agents for the treatment of HIV infection. Several phase I studies were conducted in healthy volunteers over the course of clinical development to evaluate whether pharmacokinetic drug—drug interactions exist between emtricitabine and other nucleoside antivirals that are extensively eliminated by renal excretion. Potential interactions with stavudine and famciclovir were evaluated in single‐dose studies, whereas interactions with zidovudine and its major metabolite, zidovudine glucuronide, were evaluated in a multiple‐dose study. Plasma pharmacokinetic profiles and, in some studies, urinary excretion data were evaluated when each drug was administered alone and in combination with emtricitabine. Safety and plasma pharmacokinetic profiles of each drug administered alone or with emtricitabine were consistent with historical data. Statistical analyses indicated that there were no significant interactions between emtricitabine and these 3 nucleoside antivirals.