Drug dissolution profiles from polymeric matrices: Data versus numerical solution of the diffusion problem and kinetic models

This paper presents a comparative study between the data collected in a drug dissolution experiment and the predictions obtained from simple mathematical approaches of drug diffusion in the delivery device and also with the results achieved from available kinetic models for dissolution processes. The controlled release of timolol maleate from a hydrogel disc, obtained by thermal copolymerization of hydroxyethyl methacrylate and methacrylic acid, was used as the case study. The equilibrium parameter (drug partition coefficient) used to model the mass transfer process dictates the predictions’ accuracy. When this parameter is calculated from the drug release experiment, the diffusion equation with a Robin boundary condition type gives good predictions of the dissolution process. Predictions obtained with zero-sink condition in the release medium resulted in an overestimation of data. Several kinetic models available in the literature to describe drug release were used to correlate data. All the models tested describe the data adequately, but the Weibull model was the one that had the best correlation performance