Gastroretentive dosage forms

Gastroretentive dosage forms are drug delivery systems which remain in the stomach for an extended period of time, and allow both spacial and time control of drug liberation. Their application can be advantageous in the case of drugs that are absorbed mainly from the upper part of the gastrointestinal tract or are unstable in the medium of distal intestinal regions. They can also be used beneficially in the local therapy of the stomach. Because of the complicated and by many factors influenced physiology of this organ, the design of such delivery systems is a task requiring due foresight and knowledge. Gastroretentive dosage forms can be floating, expandable, bioadhesive, modified shape and high density systems according to the physical property leading to prolongation of gastric residence time. Combinations of the listed categories can occur as well. Several spirited ideas and solutions have come up in the literature for the preparation of such delivery systems, but there is still need for development in the field of implementation and prediction of in vivo behaviour before these dosage forms can be elemental part of clinical practice.