Gastric retentive drug-delivery systems.

The development of a long-term oral controlled-release dosage form has been difficult mainly because of the transit of the dosage form through the gastrointestinal (GI) tract. Several approaches to extend gastric residence time have been tried. The most commonly used systems are (1) intragastric floating systems, (2) high-density systems, (3) mucoadhesive systems, (4) magnetic systems, (5) unfoldable, extendible, or swellable systems, and (6) superporous hydrogel systems. The concept of each approach is examined, and improvements that are needed for further development are discussed. Background materials in the GI physiology that are necessary for understanding the concept and usefulness of each approach are also provided.