RESUMO
Ethylene vinyl acetate intravaginal rings (IVRs) were prepared by hot-melt compounding and injection moulding. The IVRs contained various levels of the antiretroviral drug UC781 and the contraceptive hormone levonorgestrel. The IVRs were assayed for drug content and related substances, characterized for physical properties, in vitro drug-elution kinetics, photostress stability, and 3-month accelerated storage stability under ICH conditions. UC781 degrades on exposure to light and during thermal processing. UC22 is the major degradant of UC781. Drug release rates were proportional to drug loading, independent of the other drug in combination with IVRs, and were stable for 3 M at 40°C/75% RH despite changes in the appearance of the IVRs which is tentatively ascribed to crystallization of UC781 at or near the surface of the IVRs. The behavior of UC781 poses a substantial barrier to the commercial development of these IVRs.