Synonyms: Risperidone Imp. I (EP),4H-Pyrido[1,2-a]pyrimidin-4-one, 3-[2-[4-[4-fluoro-2-[4-(6-fluoro-1,2-benzisoxazol-3-yl)-1-piperidinyl]benzoyl]-1-piperidinyl]ethyl]-6,7,8,9-tetrahydro-2-methyl-, 3-[2-[4-[4-Fluoro-2-[4-(6-fluoro-1,2-benzisoxazol-3-yl)-1-piperidinyl]benzoyl]-1-piperidinyl]ethyl]-6,7,8,9-tetrahydro-2-methyl-4H-pyrido[1,2-a]pyrimidin-4-one, 3-[2-[4-[4-Fluoro-2-[4-(6-fluoro-1,2-benzisoxazol-3-yl)piperidin-1-yl]benzoyl]piperidin-1-yl]ethyl]-2-methyl-6,7,8,9-tetrahydro-4H-pyrido-[1,2-a]pyrimidin-4-one