Systems approach to vaginal delivery of drugs III: Simulation studies interfacing steroid release from silicone matrix and vaginal absorption in rabbits.

A composite physical model involving the simultaneous receding boundary release of drug from a drug suspension-silicone polymer matrix system, diffusion across the aqueous layer, and passive transport across the vaginal membrane consisting of parallel lipoidal and aqueous pore pathways is described. Simulation studies with progesterone and hydrocortisone illustrate matrix release-limiting, membrane absorption, and aqueous diffusion layer-limiting cases when the cylindrical silicone delivery device is interfaced with the vaginal membrane of the rabbit.