Pharmacokinetics of Lamivudine, Zidovudine, and Nevirapine Administered as a Fixed‐Dose Combination Formulation Versus Coadministration of the Individual Products

The pharmacokinetics of 150 mg lamivudine, 300 mg zidovudine, and 200 mg nevirapine were assessed following single oral administration of a fixed-dose combination tablet and coadministration of the separate innovator products in healthy male subjects (n = 64) under fasting conditions in an open-label, randomized, 2-way crossover study. Multiple blood samples were collected up to 72 hours and plasma concentrations of antiretrovirals were assayed using liquid chromatography/tandem mass spectrometry methods. Pharmacokinetic parameters were calculated using noncompartmental methods, and bioequivalence was assessed using an analysis of variance model. The ratio of the least squares mean (fixed-dose combination to individual products) and 90% confidence intervals of AUC(0-t), AUC(0-infinity), and C(max) for lamivudine, zidovudine, and nevirapine were all within 80.0% to 125.0%, suggesting a similar rate and extent of antiretroviral exposure in the bloodstream. Mean oral clearance (CL/F) values of lamivudine, zidovudine, and nevirapine for the fixed-dose combination were 23.7, 127, and 1.65 L/h, respectively. The fixed-dose combination and individual products were equally safe and well tolerated, with only a few subjects experiencing drug-related adverse events. The current fixed-dose combination of lamivudine, zidovudine, and nevirapine is expected to provide a similar efficacy/safety profile as coadministration of the individual products, a better adherence to treatment, and considerable cost savings in the treatment of HIV.