Patent ID: 6787156
Filing Date: 2004-09-07
Classification: A61K

Abstract:
A composition for controlled delivery of at least one active substance into an aqueous medium by erosion of at least one surface of the composition, wherein said erosion occurs at a preprogrammed rate, comprisingi) a matrix comprising the active substance, wherein the matrix is erodible in the aqueous medium in which the composition is used and wherein the matrix allows substantially no diffusion of water into the composition beyond any exposed surface layers of the matrix, and ii) a coating having at least one opening exposing at least one surface of said matrix, the coating comprising a) a first cellulose derivative which has thermoplastic properties and which is substantially insoluble in the aqueous medium in which the composition is used, and at least one of b) a second cellulose derivative which is soluble or dispersible in water, c) a plasticizer, and d) a filler, wherein said coating crumbles and/or erodes upon exposure to the aqueous medium, at a rate which is equal to or slower than the rate at which the matrix erodes in the aqueous medium, allowing controlled exposure of said surface of the matrix to the aqueous medium.