In vitro controlled release of theophylline from tablets containing a silicone elastomer latex

Abstract

Abstract Two batches of controlled-release theophylline tablets were prepared using a silicone elastomer latex, one batch by the wet granulation process, the other by direct compression. In the wet granulation process, a dispersion consisting of silicone elastomer latex and fumed silica was used as the granulation fluid, whereas in the direct compression process, a dry, silica-filled silicone elastomer powder prepared from the latex was employed. The release profile of theophylline from the tablets prepared by wet granulation suggests that a matrix-diffusion controlled drug-release mechanism was at work. On the other hand, the directly compressed tablets displayed a drug-release profile that is explained by a matrix-eorosion mechanism. Tablets prepared by direct compression resulted in a faster drug-release rate when compared with the rate of those tablets prepared by wet granulation, even though both batches of tablets had the same formulation. In both the wet granulation and direct compression processes, tablets with a higher percent of silicone elastomer exhibited a slower drug-release rate. Directly compressed tablets formulated with a silicone elastomer powder containing a higher percentage of silica showed a faster drug-release rate. With all other factors unchanged, when a smaller particle size of silicone elastomer powder was used in the direct compression process, tablets with a slower drug-release rate were formed. The effect of the pH of the dissolution medium on the drug-release rate was found to be insignificant.