Physiology of the colorectal barrier

The colon is a suitable site for the safe and slow absorption of drugs which are targetted at the large intestine or designed to act sytemically. The physiology of the colorectal barrier is complex and influenced by many factors including diet, bacterial metabolism and colonic mixing and transit time. As the motility and absorption characteristics of the colon change from the proximal colon to the rectum, the physiology of these regions and the likely residence time of any drug at each site must be understood for the full potential of the colon to be exploited. This article will discuss the main physiological factors affecting the colon and hence colonic drug absorption. (C) 1997 Elsevier Science B.V.