Characterization of dual layered pellets for sustained release of poorly water-soluble drug

The aim of this study was to develop pellet formulations that could be used to improve the dissolution and bioavailability of a poorly water-soluble model drug, cisapride. Six different types of pellets were prepared by coating sugar spheres in a fluidized bed coater. When the sugar spheres were single layered containing cisapride and solubilizer such as polysorbate 80, the resulting pellets provided an instant release of cisapride in the simulated gastric fluid. Dissolution tests carried out in the simulated intestinal fluid showed that there were negligible amounts of cisapride released, regardless of the pellet formulation. To succeed in attaining dissolution and the sustained release of cisapride at a neural pH, the single layered pellets were coated again with a coating suspension containing Eudragit RS 30D and L 30D. Scanning electron microscopy revealed that the dual layered pellets had a crack-free and spherical surface. Interestingly, the dual layered pellets provided the sustained release of cisapride in both the simulated gastric and intestinal fluids. The composition and components of the dual layers were found to be key parameters affecting the pattern of cisapride dissolution. Significant improvement in the bioavailability of cisapride was achieved when the dual layered pellets were administered orally to dogs. Overall, these results suggest that the dual layered pellets have potential as a sustained release dosage form for poorly water-soluble drugs.