Gastroretentive controlled release pharmaceutical dosage forms

A foldable pharmaceutical gastroretentive drug delivery system for the controlled release of an active agent in the gastrointestinal tract, which system comprises:

• a) a single- or multi-layered matrix having a two- or three-dimensional geometric configuration comprising a polymer that does not retain in the stomach more than a conventional dosage form, said polymer selected from the group consisting of:
• (1) a degradable polymer selected from:
• (i) a hydrophilic polymer which is not instantly soluble in gastric fluids;
• (ii) an enteric polymer substantially insoluble at pH less than 5.5;
• (iii) a hydrophobic polymer;
• and
• (iv) any mixture of at least two polymers as defined in (i), (ii) or (iii);
• (2) a non-degradable polymer;
• and
• (3) a mixture of at least one polymer as defined in (1) with at least one polymer as defined in (2);
• b) a continuous or non-continuous membrane, that does not retain in the stomach more than a conventional dosage form, affixed or attached to said matrix, said membrane comprising at least one polymer having a substantial mechanical strength;
• and
• c) a drug, which may be in a particulate form or optionally contained within a drug-containing means;
• said drug or drug contained within said drug-containing means being embedded in a layer of said matrix, or being entrapped between at least two layers of said matrix, or being attached to said delivery system,
• wherein said matrix when affixed or attached to said membrane prevents evacuation from the stomach of said delivery system for a period of time of from about 3 to about 24 hours.