Colonic Delivery

Abstract

There are a number of colonic diseases that could be treated more effectively using a colon-specific delivery system. These include ulcerative colitis, colorectal cancer, and Crohn’s disease (Hanauer and Kirsner, 1988; Riley, 1993). The local delivery of drugs such as anti-inflammatory agents, anticancer agents, and antibiotics to the colon should permit lower dosing resulting in fewer side effects and increasing therapeutic efficacy. The principal goals of colon-specific delivery after oral administration are, first, to avoid absorption and biodegradation of drugs in the upper intestine such as in the stomach and small intestine where acidor enzyme-labile drugs are degraded and most small drug molecules are absorbed and, second, to release drugs site-specifically in the lower intestine such as in the cecum and colon. With these goals in mind, many different colon-specific drug delivery systems have been investigated during the last decade (Friend, 1992; Rubinstein, 1995; Hovgaard and Brønsted, 1996; Kinget et al., 1998; Sinha and Kumria, 2001). Among these, the most important are film-coating of drug formulations with pH- or pressure-sensitive polymers, coating with bacterial degradable polymers, delivering drugs from time-dependent formulations or biodegradable matrices, and delivering drugs from small molecule prodrugs or polymeric conjugates. The prod rugapproach to colonic delivery is currently used to treat inflammatory bowel diseases (IBD), in which active drugs are liberated by the action of bacterial enzymes such as azo-reductase, glucosidases, and glucronidases in the colon (Friend, 1992; Sinha and Kumria, 2003).