A sustained-release coated pharmaceutical tablet comprising a drug-containing tablet and a coating or membrane surrounding the same, wherein the coating or membrane is water-insoluble and insoluble in gastrointestinal fluids and consists essentially of a terpolymer of polyvinylchloride, polyvinylacetate,...http://www.google.com/patents/US4629619?utm_source=gb-gplus-sharePatent US4629619 - Membrane-coated sustained-release tablets and method
