Systems for region selective drug delivery in the gastrointestinal tract: biopharmaceutical considerations

Background: The design of a proper region-specific oral drug delivery system has to take into consideration the differences in anatomy, physiology and absorption characteristics that exist between segments within the gastrointestinal (GI) tract, as well as transit kinetics of the dosage form and the site of drug release within the GI tract. Objective: The aim of this review is to examine the various biopharmaceutical aspects of region-specific drug delivery in the GI tract. Methods: This review is mainly focused on pharmacokinetic and pharmacodynamic aspects of region-selective drug delivery with special emphasis on drug absorption pathways (para- and transcellular, absorption and efflux transporters, lymphatic uptake etc.). It includes a discussion of gastroretentive systems, colonic delivery, and lipid-based formulations. The review also addresses targeted therapy of local diseases within the GI tract. Conclusions: The advances in pharmaceutical technology allow for the development of a variety of region-specific drug delivery systems for oral administration to optimize local and systemic therapy.