Pharmacokinetics of antiretroviral drug varies with formulation in the target population of children with HIV-1

Abstract

The bioequivalence of formulations is usually evaluated in healthy adult volunteers. In our study in 19 HIV-1-infected Ugandan children (1.8–4 years of age, weight 12 to <15 kg) receiving zidovudine, lamivudine, and abacavir solutions twice a day for ≥24 weeks, the use of scored tablets allowed comparison of plasma pharmacokinetics of oral solutions vs. tablets. Samples were collected 0, 1, 2, 4, 6, 8, and 12 h after each child’s last morning dose of oral solution before changing to scored tablets of Combivir (coformulated zidovudine + lamivudine) and abacavir; this was repeated 4 weeks later. Dosenormalized area under curve (AUC)0–12 and peak concentration (Cmax) for the tablet formulation were bioequivalent with those of the oral solution with respect to zidovudine and abacavir (e.g., dose-normalized geometric mean ratio (dnGMR) (tablet:solution) for zidovudine and abacavir AUC0–12 were 1.01 (90% confidence interval (CI) 0.87–1.18) and 0.96 (0.83– 1.12), respectively). However, lamivudine exposure was ~55% higher with the tablet formulation (AUC0–12 dnGMR = 1.58 (1.37–1.81), Cmax dnGMR = 1.55 (1.33–1.81). Although the clinical relevance of this finding is unclear, it highlights the impact of the formulation and the importance of conducting bioequivalence studies in target pediatric populations.