Comparative pharmacokinetics of two different formulations of efavirenz

The use of generic drugs assumes importance given the increasing availability of antiretroviral therapy in developing countries. The purpose of this study was to determine the pharmacokinetics and comparative bioavailability of a NNRTI. efavirenz, manufactured by a local drug company (T - Virorrever(R), Richmond Laboratories) against the innovator pharmaceutical product (R - Stocrim(TM), Merck). Pharmacokinetic parameters including AUC (0-->infinity) AUC (0-->144h), Cmax, Tmax and T-1/2 were determined from plasma concentrations of 18 healthy volunteers by means of a randomized two-way crossover design for 200mg tablets of both formulations. Geometric averages (antilogarithmic) and 90% confidence intervals for AUC (0-->infinity), AUC (0-->144h) and Cmax were 0.9890 (0.8010-1.2210), 1.0014 (0.8653-1.1589) and 0.9348 (0.8196-1.0661) respectively, satisfying the 80-125% bioequivalence range accepted by the FDA, the EMEA and the WHO guidances. Bioequivalence between the test and reference formulation can be concluded.