Oral delayed-release system for colonic specific delivery

The paper describes a novel oral time-based drug release system for colonic specific delivery. The system, designed to exploit the relatively constant small intestine transit time of dosage forms, consists of drug-containing cores coated with three polymeric layers. The outer layer dissolves at pH > 5, then the intermediate swellable layer, made of high-viscosity HPMC, interacts slowly with aqueous fluids, thus providing the delay phase. The inner film is made of an enteric material. The system provides the expected delayed release pattern, as also indicated by the preliminary in vivo experiments on rats.