Abstract
Theoretically expected rates of release of solid drugs incorporated into solid matrices have been derived for several model systems. Mathematical relations have been obtained for cases (a) where the drug particles are dispersed in a homogeneous, uniform matrix which acts as the diffusional medium and (b) where the particles are incorporated in an essentially granular matrix and released by the leaching action of the penetrating solvent. A number of technological factors are influencing the formulation of sustained release tablets. It was found that the choice of matrix material, amount of drug incorporated in matrix, matrix additives, the hardness of the tablet, density variation, and tablet shape could markedly affect the release rate and also the formulation.