Hydration, Swelling, Erosion and Drug Release from HPMC and HPMC/TP Matrices

This work was focused on studying the phenomena which occur during the hydration of solid pharmaceutical systems to administrate via oral route. These systems were made by direct compression of the only HydroxyPropyl-MethilCellulose (HPMC, a swelling hydrogel) and of the powder mixtures containing both HPMC and Theophylline (TP, a drug used against respiratory diseases) in different ratios. These matrices were immersed in distilled water at 37 C, allowing the water up-take and the drug release only by lateral surface, by confining the cylindrical matrix tablets between two glass slides. The tablets, after given immersion times, were withdrawn and cut in several annuli, which in turn were analyzed to get the drug and the water concentration profiles along radial direction. The results confirmed the pseudo-diffusive nature of the process, and allowed to obtain detailed information about controlled drug release process from matrices made of swellable hydrogels.