Heterogeneous model of drug release from polymeric matrix.

The kinetics of drug release from a polymeric matrix originally proposed by Higuchi were extended for the case of high drug loading (relative to the solubility of the drug in the polymer). The model of a granular matrix in which an effective porosity and tortuosity are assumed to modify the normal Higuchi kinetics is reviewed. A new model, which allows the prediction of the kinetics of drug release from properties of the polymer and drug, is based on the assumption that the permeability of the dispersed matrix is a function of drug loading.