Conventional solid oral modified release dosage forms that use polymers to alter the time and/or site at which drug release occurs often result in variable and poor in vivo performance in humans. The variability can be attributed, in part, to the large size of normal dosage forms such as tablets, capsules, pellets or granules and the biopharmaceutic interaction of these dosage forms within the gastrointestinal tract (GIT). The human GIT is a physiologically heterogeneous environment and factors such as pH (1), fluid volume (2), and transit times (3) will impact on dosage form behavior. For example, the onset of drug release from enteric coated formulations is unpredictable due to delayed gastric emptying, particularly when dosing occurs after food (4), and the fact that such products may take up to 2 hours to disintegrate in the small intestine (5,6). In addition, modified release dosage forms designed for colon targeting have been found intact in the feces (7,8).