Characteristics of Natural Polysaccharides for Colon Drug Targeting

Targeting drugs directly to the colon is advantageous in the topical treatment of colonic diseases such as ulcerative colitis and Crohn’s disease and has shown potential in gaining the oral delivery of peptides and other labile drugs. A colonic drug delivery system is required to protect a drug during its transit through the upper gastro-intestinal (G.I.T.) tract and allow its release in the colon. Several methods of colonic targeting have been proposed. These include taking advantage of the apparent consistency of small intestinal transit times, the utilization of pH changes within the G.I. tract and the exploitation of bacterial enzymes localized in the colonic region of the G.I. tract. Among the different approaches to achieve targeted drug release to the colon, the use of polymers especially biodegradable by colonic bacteria holds great promise. Polysaccharides are bacterial enzymes that are available in sufficient quantity to be exploited in colon targeting of drugs. Based on this approach, various polysaccharides have been investigated for colon-specific drug release. These polysaccharides include pectin, guar gum, amylose, inulin, dextran, chitosan, and chondroitin sulfate. This family of natural polymers has an appeal to drug delivery as it is comprised of polymers with a large number of derivatizable groups, a wide range of molecular weights, varying chemical compositions, and, for the most part, low toxicity and biodegradability yet high stability. The most favorable property of these materials is their approval as pharmaceutical excipients. Polysaccharides are bacterial enzymes that are available in sufficient quantity to degrade these natural polysaccharides.