Patent ID: 8507527

Claim:
A method for stabilizing donepezil or a pharmaceutically acceptable salt thereof that is in contact with ethylcellulose, comprising adding a methacrylic acid-ethyl acrylate copolymer in a mixture comprising the donepezil or a pharmaceutically acceptable salt thereof, the ethylcellulose, and a water-soluble sugar or sugar alcohol during a mixing or granulation step and preparing a sustained-release matrix-type pharmaceutical composition comprising the donepezil uniformly distributed with the ethylcellulose and the methacrylic acid-ethyl acrylate copolymer, wherein the sustained-release matrix-type pharmaceutical composition comprises the ethylcellulose in an amount of 12% to 32% by weight, and the methacrylic acid-ethyl acrylate copolymer in an amount of 15.8% to 37% by weight.