ABSTRACT
This chapter reviews oral controlled-release (CR) systems, with a focus on dosage-form characteristics and gastrointestinal (GI) physiology. Since an understanding of the basic concepts of CR systems is vital for future development, the chapter emphases on the rationale and mechanism of such delivery systems. The term CR implies a system that provides continuous delivery of the drug for a predetermined period with predictable and reproducible kinetics, and known mechanism of release. The chapter deals with dosage forms intended to be swallowed orally and excludes buccal and rectal areas of delivery. It details first-pass metabolism on pharmacokinetic and pharmacodynamic considerations. The chapter focuses on the basic principles involved in conception and development of new approaches to oral CR drug-delivery systems. It emphases on the rationale of design of systems and their interaction with the GI environment. The design of oral CR dosage forms is aimed at presenting the drug to the absorptive membrane of the GI tract at a predetermined rate.
