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In this talk I will present a mathematical model describing the release from a drug delivery system, such as a coronary eluting stent or a transdermal patch. The problem is reduced to a dynamics of a two-phase substance between two coupled media of different properties and extents. The first layer is a polymeric platform where the drug is initially contained, and the other one is the biological tissue where the drug is directed to. A system of nonlinear partial differential equations describes the dissolution in the first layer and the saturable reversible binding in the second one, with an interface condition is imposed across the two layers. A finite difference scheme is used to discretize spatially the problem and a Runge-Kutta type method with backward differentiation formulas and adaptive time step is adopted. The typical drug dynamics, the concentration levels, the optimal delivery rate will be shown and discussed in some case studies. The results are used to discuss the roles of the diffusion and reaction parameters, to evaluate drug release efficacy in the design of advanced delivery systems.
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