Most of the conventional drug delivery systems for treating the colonic disorders are failing as the drugs do not reach the site of action in appropriate concentrations. Colon-specific drug delivery is designed to target drug molecules specifically to this area. Compression coated tablet is one of the approach to target colon and avoid drug release in the gastrointestinal tract. 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. Development of site-specific delivery systems may exploit a specific property of the target site for drug release. The gastrointestinal tract is occupied by over 400 bacterial species, each having a specific role 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. In compression coated tablet core tablet is coated with coating material which is degraded by enzyme in the colon. 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. In this article natural polymers are given that are used for compression coating with their role.
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