Oral colon-specific drug delivery: Design strategies

Increasing interest is directed to delivery systems able to control the site of release. In this respect, colon-specific drug delivery has been suggested for the local treatment of inflammatory bowel diseases, the control of colonic bacterial growth and the improvement of the bioavailability of orally administered polypeptides and proteins. Various approaches have been attempted incuding the use of prodrugs, coatings degraded by microflora enzymatic activity, and polymeric coatings which dissolve at specific pH. Another strategy relies on the exploitation of the relative constant small intestine transit time of pharmaceutical dosage forms. This article includes the rational basis for various approaches, the general aspects relevant to the design and technological features of colon-specific drug delivery systems, together with their classification and definition.