Table 1.

Systems for extending gastric residence of an oral dosage form.

Gastric Residence Approach	Description
Floating	System is less dense than gastric fluid and remains buoyant in the stomach, reducing probability of drainage. Two major types of flotation-based systems are low density and gas forming systems.
Swellable	System swells in the stomach and is retained as long as its size is too large to permit passage through the pylorus and/or a house keeping wave is able to expel.
Expandable	System expands or unfolds to a geometry that can prevent passage through the pylorus. Gastric residence is achieved through a combination of size and biomechanics.
Mucoadhesive	System reversibly adheres to the mucosal surface of the stomach and prolongs retention until displacement or loss of adhesion, or turnover of the mucous layer
High Density	System is more dense than gastric contents and sinks to the bottom of the stomach and is preferentially retained in gastric folds
Magnetic	A magnet is placed in the abdomen next to the stomach and the system is retained in the stomach through magnetic immobilization.