Drugs 2005; 65 (14): 1991-2007 REVIEW ARTICLE 0012-6667/05/0014-1991/$39.95/0 © 2005 Adis Data Information BV. All rights reserved. Advances in Colonic Drug Delivery Abdul W. Basit The School of Pharmacy, University of London, London, England Contents Abstract ................................................................................... 1991 1. Rationale for Targeting Drugs to the Colon ................................................ 1991 2. Colonic Anatomy and Physiology, and Implications for Drug Delivery ........................ 1992 3. Strategies for Targeting Drugs to the Colon ................................................ 1993 3.1 Means of Effecting Drug Release ..................................................... 1993 3.1.1 Gastrointestinal pH ............................................................ 1993 3.1.2 Gastrointestinal Transit Times ................................................... 1997 3.1.3 Gastrointestinal Pressure ....................................................... 1998 3.1.4 Gastrointestinal Bacteria ....................................................... 1999 4. Conclusions ............................................................................ 2003 Targeting drugs and delivery systems to the colonic region of the gastrointesti- Abstract nal tract has received considerable interest in recent years. Scientific endeavour in this area has been driven by the need to better treat local disorders of the colon such as inflammatory bowel disease (ulcerative colitis and Crohn’s disease), irritable bowel syndrome and carcinoma. The colon is also receiving significant attention as a portal for the entry of drugs into the systemic circulation. A variety of delivery strategies and systems have been proposed for colonic targeting. These generally rely on the exploitation of one or more of the following gastrointestinal features for their functionality: pH, transit time, pressure or microflora. Coated systems that utilise the pH differential in the gastrointestinal tract and prodrugs that rely on colonic bacteria for release have been commercialised. Both approaches have their own inherent limitations. Many systems in development have progressed no further than the bench, while others are expensive or complex to manufacture, or lack the desired site-specificity. The universal polysaccharide systems appear to be the most promising because of their practicality and exploitation of the most distinctive property of the colon, abundant microflora. 1. Rationale for Targeting Drugs to gies of the colon. These disease states range in the Colon severity from constipation and diarrhoea, to irritable bowel syndrome and inflammatory bowel disease The challenge of targeting drugs to the colonic (ulcerative colitis and Crohn’s disease), through to region of the gastrointestinal tract is one that has infection and colon carcinoma. While some of these been embraced by scientists over the past two de- disorders are fairly innocuous, the majority are cades. [1-6] Work in this area has been driven primari- ly by the need to improve the treatment of patholo- debilitating and life threatening. For example,