Nevirapine, stavudine and lamivudine pharmacokinetics in African children on paediatric fixed-dose combination tablets

Objective: Triomune Baby and junior have been developed in response to the urgent need for appropriate paediatric fixed-dose combination antiretroviral tablets, with higher nevirapine to stavudine and lamivudine ratios than adult tablets, in accordance with paediatric recommendations. We determined whether this ratio results in optimal exposure in the target population. Methods: Seventy-one Zambian children were treated with Triomune Baby or junior dosed according to weight bands. After 4 weeks or more, a 12-h pharmacokinetic curve was recorded. Antiretroviral plasma concentrations were assayed by high-performance liquid chromatography. Results: Six children were excluded because of poor adherence. Of the remaining 65, 24 (37%) were female, 24 (37%) weighed less than 15 kg and most were malnourished. Mean (range) nevirapine C-12h, C-max and AUC(12h) of 6.0 (1.4, 16.9)mg/l, 10.0 (3.8, 22.5) mg/l and 94.4 (32.1, 232) mg/1 per hour were higher than those reported in adults. Nevirapine C-12h was subtherapeutic (< 3.0 mg/l) in four children (6%). Mean stavudine and lamivudine C-12h, C-max, AUC(12h) (< 0.015 mg/l, 0.45 mg/l, 1.05 mg/l per hour and 0.09 mg/l, 1.33 mg/l, 5.42 mg/1 per hour) were comparable to adults. There was no evidence of a difference in nevirapine AUC(12h) across weight bands (P=0.2), whereas the difference in stavudine (P= 0.0003) and lamivudine AUC(12h) (P= 0.01) was driven by the single weight band with unequal dosing. Conclusion: Nevirapine concentrations were higher but more variable than in adults; the pharmacokinetic parameters of stavudine and lamivudine were comparable to adults. As nevirapine underdosing is of greater concern than overdosing, the Triomune Baby and junior ratio appears to be appropriate for children weighing 6 kg and over. Further research is required for children under 6 kg. (C) 2008 Wolters Kluwer Health Lippincott Williams & Wilkins.