Extrusion–spheronization of pH-sensitive polymeric matrix pellets for possible colonic drug delivery

Abstract

The aim of this study was to investigate extrusion–spheronization pelletization for preparing pH-sensitive matrix pellets for colon-specific drug delivery. The effects of three independent variables (amounts of Eudragit™ S, citric acid and spheronizing time) on pellet size, shape (roundness and aspect ratio), and drug release were studied with central composite design. The pellets contained ibuprofen as a model drug, citric acid as a pH-adjusting agent, Eudragit™ S as a pH-sensitive binder and microcrystalline cellulose (MCC). The pellets were prepared with Nica extrusion–spheronizing equipment and subsequently enteric-coated using an air-suspension technique. Eudragit™ S as a pH-sensitive matrix former in pellets increased the pellet size and influenced pellet roundness. In small amounts Eudragit™ S increased pellet roundness but in larger amounts pellet roundness was reduced. Citric acid promoted the pelletization process resulting in a narrower area distribution . The pH-sensitive matrix pellet failed to delay the drug release . The combination of citric acid and enteric coating, however, delayed the drug release for 15 min in a pH 7.4 phosphate buffer.