Pharmacokinetic comparison of generic and trade formulations of lamivudine, stavudine and nevirapine in HIV-infected Malawian adults.

BACKGROUND

The Malawian antiretroviral program uses generic Triomune (stavudine, lamivudine, and nevirapine).

OBJECTIVE

To determine the pharmacokinetics and bioequivalence of generic and trade formulations of stavudine, lamivudine, and nevirapine in HIV-infected Malawians.

METHODS

This randomized, open label, cross-over study comprised of six men and six women currently receiving Triomune-40 TM who were randomized to the generic or trade formulation of stavudine (40 mg twice daily), lamivudine (150 mg twice daily) and nevirapine (200 mg twice daily). After at least 21 days, the alternate formulation was administered. At the end of each period, six blood samples were collected over 8 h. Bioequivalence was achieved if the 90% confidence interval (CI) for the geometric mean ratio (GMR) of generic:trade formulations for maximum plasma concentration (Cmax) and the area under the concentration-time curve (AUC) was within 0.8-1.25.

RESULTS

Mean patient age, weight, and height were 38.4 years (SD, 7.7), 71.2 kg (SD, 7.0), and 164.8 cm (SD, 6.3), respectively. The GMR for stavudine, lamivudine, and nevirapine were 1.4 (90% CI, 1.2-1.7), 1.1 (90% CI, 0.8-1.6), and 0.9 (90% CI, 0.7-1.2), respectively, for Cmax; and 1.1 (90% CI, 1.0 1.2), 1.0 (90% CI, 0.7-1.3), and 0.9 (90% CI, 0.7-1.1), respectively, for AUC0-8h. Regardless of formulation, Malawians had higher nevirapine exposures compared with historical reports of Western HIV-infected patients.

CONCLUSIONS

Although exposures were similar, Triomune did not meet the strict definition of bioequivalence for these drugs. Patients taking Triomune had notably higher stavudine Cmax values. Antiretroviral pharmacokinetics and bioequivalence of generic formulations should be evaluated in the populations in which they are being used.