Microbially triggered drug delivery to the colon.

Increasing acceptance of protein- and peptide-based drugs necessitates an investigation into the suitability of various sites for their administration. Colon is being investigated for delivery of such molecules. Colon-specific drug delivery is designed to target drug molecules specifically to this area. Development of site-specific delivery systems may exploit a specific property of the target site for drug activation/release. The gastrointestinal tract is inhabited by over 400 bacterial species, each having a specific niche in the tract. Colon, the distal part of the intestine is inhabited by a large variety of gram negative microflora. This flora produces a vast number of enzymes which are being exploited for formulation of colon-specific drug delivery systems. A number of microbially activated systems for colon-specific drug delivery are being evaluated. These include prodrugs and synthetic or natural polymer-based delivery systems. This article aims at reviewing the various microbially activated drug delivery systems for colon-specific drug delivery with specific reference to the microflora of the various segments of the gastrointestinal tract and their role in targeting drug delivery to the colon.