Bioequivalence of dispersed stavudine: opened versus closed capsule dosing

Stavudine, a nucleoside reverse transcriptase inhibitor, is used commonly to treat HIV-infected children in the developing world. The paediatric liquid formulation presents major logistical difficulties in rural and resource-limited areas, and prescribers are frequently forced to employ off-label 'opened capsule' dosing methods using the adult capsule. The South African Department of Health (DoH) has advised that caregivers should be instructed to disperse the contents of an adult capsule in 5 ml water and then withdraw the required dose using a syringe. The bioavailability of stavudine using the opened capsule dosing method has not previously been validated.

This was a randomized crossover pharmacokinetic study with each subject serving as his/her own control. A total of 28 healthy HIV-negative adult volunteers were randomized on a 1:1 basis to receive one of the two generic preparations typically available in state hospitals. They were then further randomized to receive either intact or opened 30 mg capsules. After 1 week, those who initially received intact capsules, were given opened capsules and vice versa. The capsule dispersion technique used was identical to that prescribed by the DoH. Serial blood samples were collected and plasma stavudine concentrations were assayed by liquid chromatography tandem mass spectrometry. Stavudine pharmacokinetics were analysed using non-compartmental methods and formulations were compared using ANOVA.

Plasma drug exposure after stavudine administration as a solution using an opened capsule dosing method was found to be bioequivalent to intact capsule administration. This was true for both generics tested.

The opened capsule dosing technique is bioequivalent to intact capsule dosing for stavudine in HIV-seronegative adults.