SWELLING AND DRUG-RELEASE IN HYDROGEL MATRICES - POLYMER VISCOSITY AND MATRIX POROSITY EFFECTS

Hydroxypropylmethylcellulose (HPMC) represents the most frequently used polymer in the formulation of hydrogel matrices for controlled drug delivery. Drug release from these matrices is related to the area exposed to the dissolution medium. This work focused on the release of buflomedil pyridoxalphosphate from hydrogel matrices containing HPMC having different grades of viscosity and partially coated with an impermeable film. Drug release was discussed as a function of the dimensional modification of the matrices during release. It was found that the release kinetics is controlled by the increase in releasing area produced by the swelling phenomenon. The presence of an impermeable coating on the hydrogel matrix changes the swelling kinetics, and as a consequence the systems can become more liable to erosion. Drug release is slightly influenced by the viscosity of the polymer. The initial porosity of the hydrogel matrices, in the range studied, does not affect drug release.