a gastro - retentive drug delivery system for controlled release of drugs in the stomach or upper gastro - intestinal track provides one or more polymers that hydrate and swell to immobilize the drug in situ in a protective , degradable envelope or cocoon . in one embodiment , oppositely charged polyelectroytes are admixed with the drug and filled in a capsule having a dissolution profile in stomach acid at body temperature . the dissolution profile of the capsule promotes formation of a poyelectrolyte gel complex . the gel complex increases retention time of the drug and reduces dosing requirements , increases absorption , reduces dose - dependent side effects , and provides reproducible , time - controlled drug residence in the gi tract .