DRUG-RELEASE FROM SILICONE MATRICES .1. INFLUENCE OF FORMULATION AND SHAPE FACTORS

The aim of this study was to prepare inert matrices of prednisolone em ploying silicone elastomer (siliastic 382 medical grade) as a matrix m aterial. A various formulations were prepared to investigate the effec t of particle size of active material, type and concentration of co-so lvents and the geometrical shape of formulations on the release of act ive material. The release rate of active material were determined by t he use of flow through cell and static method for a period of 6 hours and one month respectively. In order to evaluate the parameters affect ing the release of active material, a number of physicochemical parame ters related to active material such as solubility in dissolution medi a and in the matrix material, partition coefficient and diffusion coef ficient in the matrix material were investigated. The changes in surfa ce area and the weight of the dosage forms during the dissolution peri ods were also determined. As a result of this study, it was found that the release of active material was mainly governed by the presence of co-solvents and the geometrical shape of formulations. The particle s ize of active material had no significant effect on the release of act ive material.