DEVELOPMENT OF A NOVEL CONTROLLED-RELEASE SYSTEM FOR GASTRIC RETENTION

Purpose. We report on the development of a novel controlled-release ga stric retention system, which consists of a matrix tablet, coated with a permeable membrane. When immersed in simulated gastric fluid, the t ablet expands. The tablet remains expanded for eighteen to twenty hour s, during which time the drug is released. The tablet then either disi ntegrates into fragments or loses its integrity. Methods. Tablets cont aining a soluble drug (chlorpheniramine maleate, i.e., CPM) and a pear ly soluble drug (riboflavin 5' phosphate, i.e., R5'P) were compressed. They were coated with a permeable and elastic polymer (Eudragit(R)). Dissolution profiles of these tablets were studied. The changes in the pH, viscosity, and deformation characteristics as a function of time were measured. Results. Carbopol(R) provided a firm structure to the s wollen tablet. Polyvinyl pyrrolidone XL (PVP XL) contributed to the sw elling of the tablet. Carbonates provided the initial alkaline micro-e nvironment for Carbopol(R) to gel and conferred buoyancy to the tablet . Coating provided the support needed for the core to remain intact du ring drug release and, at the same time, it allowed drug release due t o its permeable nature. During release, the gelling properties of Carb opol(R) lessened, resulting in a decrease in the firmness of the core. This was evident from the decrease in the viscosity of the core. The energy required at 50% strain also decreased as the drug release progr essed. Conclusions. When this tablet is ingested, the chances of its e limination through the pylorus should be greatly reduced due to tablet 's expansion, and due to its disintegration or loss in integrity it sh ould then be expelled out of the stomach at the end of the drug releas e.