Method for producing fine particles of aripiprazole anhydride crystals b

Disclosed herein is a method for producing fine particles of aripiprazole anhydride crystals B less than 50 µm in size, comprising the steps of: (a) heating and dissolving crude aripiprazole in a lower alcohol selected from the group consisting of methanol and ethanol, and subsequently cooling the resulting mixture to precipitate crystals to obtain crystals of aripiprazole lower alcohol solvate; (b) subjecting the crystals of aripiprazole lower alcohol solvate to wet-milling in the form of a slurry containing the lower alcohol; and (c) subjecting the dispersion of the wet-milled crystals to solid-liquid separation to obtain the crystals, and heating the crystals to dry. In one embodiment the volume average particle size of the wet-milled crystals in step (b) is 15 to 20 µm. Aripiprazole is known as 7-{ 4-[4-(2,3-dichlorophenyl)-I-piperazinyl]butoxy} -3,4-dihydrocarbostyril or 7-{ 4-[4-(2,3-dichlorophenyl)-Ipiperazinyl]butoxy} -3,4-dihydro-2(IH)-quinolinone.