Gastrointestinal dynamics and pharmacology for the optimum design of controlled-release oral dosage forms.

This article encompasses a brief discussion of the principles of pharmacodynamics of different types of drugs and the mechanisms of absorption at different sites in the gastrointestinal tract. The importance of factors such as the pH, the unstirred layer or microclimate, gastric emptying, intestinal contact time, metabolism in the gut wall, and bacterial degradation in the colon is discussed. Methods that can be used to alter the absorption of drugs such as formulation in a viscous form, a form that floats in the stomach, position release forms, combination with other drugs that may influence absorption, etc. are examined in detail.