Mathematical models and methods in drug delivery systems

We propose a novel in-silico model for computing drug release from multi-layer capsules. The diffusion problem in such heterogeneous layer-by-layer composite medium is described by a system of coupled partial differential equations, which we solve analytically using separation of variables. In addition to the conventional partitioning and mass transfer interlayer conditions, we consider also the case of finite mass transfer resistance, which corresponds to the case of a coated capsule. The drug concentration in the core and through all layers, as well as in the external release medium, is given in terms of a Fourier series that we compute numerically to describe pharmacokinetics and to characterize the drug release mechanism.