The present invention provides an aqueous suspension preparation comprising (3aR,4S,7R,7aS)-2-{(1R,2R)-2-[4-(1,2-benzisothiazol-3-yl)piperazin-1-ylmethyl] cyclohexylmethyl}hexahydro-4, 7-methano-2H-isoindole-1,3-dione (Compound 1), a pharmaceutically acceptable acid addition salt thereof, or a mixture thereof as an active ingredient, which has the following feature (I) or (II):(I) the circularity of the suspended particle is about 0.960 or less when the preparation comprises a thickening agent,(II) the circularity of the suspended particle is about 0.945 or less when the preparation comprises no thickening agent.
