PATHOLOGICAL INFLUENCES ON COLONIC MOTILITY - IMPLICATIONS FOR DRUG DELIVERY

Targeted site-specific delivery to the colon prevents loss of drugs which frequently occurs in the upper gastrointestinal tract due to degradation by brush-border enzymes or to small intestinal absorption. Such targeted dosage forms also allow the systemic delivery of drugs over a prolonged period, exploiting the reservoir function of the right colon, and enable the delivery of drugs locally for the treatment of diseases of the proximal colon. The design of controlled-release systems for optimal drug delivery to the proximal colon requires a detailed knowledge of the relationship between particle size, colonic dispersion and colonic transit rates and of the factors which influence colonic transit rates and consequent drug bioavailability. In this article we have outlined many of approaches which have been made to characterise and quantitate colonic motility, both experimentally and in the deseased state, and have discussed the influence of eating, diet and drugs on colonic transit rates together with their implications for the design of drug delivery systems targeted at the colon.