Multiparticulate chitosan-dispersed system for drug delivery.

A multiparticulate chitosan-dispersed system (CDS), which is composed of the drug reservoir and the drug release-regulating layer, was developed for drug delivery. The drug release-regulating layer is a mixture of water-insoluble polymer and chitosan powder. The drug is released from CDS pellets in all regions of the gastrointestinal tract (from the stomach to the colon). CDS pellets containing chitosan powder were designed to dissolve chitosan powder partly in the release-regulating layer in the stomach and release part of drug. After passing through the stomach, the drug is released from CDS pellets at a constant speed in the small intestine. In the large intestine, CDS pellets were designed to disintegrate the remaining chitosan powder at an accelerated speed and the remaining drug in CDS pellets is released. The drug release rate can be controlled with the thickness of the chitosan-dispersed water-insoluble layer. Furthermore, for colon-specific drug delivery, an additional outer enteric coating is necessary to prevent drug release from CDS pellets in the stomach, because the chitosan-dispersed water-insoluble layer dissolves gradually under acidic conditions. The resulting enteric-coated CDS (E-CDS) pellets were found to permit colon-specific drug delivery. In this study, the multiparticulate CDS was adopted not only for colon-specific drug delivery but also for sustained drug release.