Patent ID: 8808669

Claim:
A gastroretentive, extended release composition for oral administration comprising: a. a graft copolymer of formula 1 which exhibits pH dependent behavior and capable of swelling at acidic pH, represented by wherein the said graft copolymer comprises: I. a backbone having the formula [A (x) B (y) C (z) ] comprising: a diol (A) selected from the group consisting of 1,2-ethane diol, 1,3-propane diol, 1,2-propane diol, 2-methyl-1,3-propane diol, 1,4-butane diol, 1,3-butane diol, 1,2-butane diol, 1,5-pentane diol, 1,6-hexane diol, 1,7-heptane diol, 1,8-octane diol, 1,9-nonane diol, 1,12-dodecane diol, 1,4-cyclohexanedimethanol and bis(2-hydroxyethyl)terephthalate, a dicarboxylic acid (B) selected from the group consisting of succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, and dodecanedioic acid or acid anhydride (B) selected from the group consisting of succinic anhydride and phthalic anhydride and an epoxy monomer (C) containing pendant unsaturation selected from the group consisting of glycidyl methacrylate and glycidyl acrylate or a diol monomer (C) containing pendant unsaturation selected from the group consisting of trimethylolpropane monomethacrylate and trimethylolpropane monoacrylate, wherein (x)=41-45%, (y)=49-53% (z)=4-7% by mole; and II. a graft which is a polymer of a vinyl pyridine monomer (D) and ‘w’ is a weight percent of the total weight of said graft copolymer such that ‘w’ is 22-52%; b. a gellable polymer, said gellable polymer selected from the group consisting of cellulosic polymers and polyalkene oxide; c. a therapeutically active agent; d. a gas generating system, said gas generating system comprising a gas generating agent and a carboxyl compound, said gas generating agent selected from the group consisting of alkali carbonates and bicarbonates; and e. pharmaceutically acceptable ingredients.