Controlled Release with Finite Dissolution Rate

We consider a two-phase generalization of the classical Higuchi model for controlled drug release. The drug is assumed to be prepared in a stent in its solid phase by immersion in a polymeric matrix, which eventually delivers the drug when it reaches the free end. We derive a single effective evolution equation, which we prove to be equivalent to the original system of two coupled PDEs. We provide analytical estimates for the asymptotic regimes of large and small diffusion. Results from numerical simulations allow us to fill the gap and to understand the behavior of the system in intermediate regimes.