چکیده (انگلیسی):

The effects of filler used in the pel-let cores (ie, waxy cornstarch or lactose) and the enteric film coat thickness on the diffusion and dis-solution of a freely soluble drug were studied. Two kinds of pellet cores containing riboflavin sodium phosphate as a model drug, microcrystalline cellu-lose (MCC) as a basic filler, and waxy cornstarch or lactose as a cofiller were film coated (theoretically weight increase 20% or 30%) with an aqueous dis-persion of cellulose acetate phthalate (CAP). The diffusion of riboflavin sodium phosphate in aqueous enteric-coated pellets was investigated using nonin-vasive confocal laser scanning microscopy (CLSM). The in vitro release tests were performed using a USP apparatus I (basket method). Diffusion of drug from the core to the film coat was found to be greater with lactose-containing pellets than with waxy cornstarch-containing pellets. The dissolution test showed that 30% enteric-coated waxy corn-starch pellets had a good acidic resistance in 0.1 N HCl solution for at least 1 hour, while the other en-teric pellet formulations failed the test. The waxy cornstarch-containing enteric pellets dissolved at SIF in less than 10 minutes. Confocal images of film-coated pellets showed that waxy cornstarch-containing pellets had less drug dissolved than re-spective lactose-containing pellets. The observa-tions were further confirmed by measurement of fluorescence intensity of riboflavin sodium phos-phate in the film coat. The dissolution test was con-sistent with the confocal microscopy results.In conclusion, waxy cornstarch as a cofiller in the pellet cores minimizes premature drug diffusion from the core into the film coat layer.