An injectable depot formulation comprising crystals having structure (I) wherein R is (FII) and the X50 value of the crystals is from 1 to 200 microns. Depot formulations containing crystals of iloperidone or its metabolites have the following advantages: (i) release of the crystals in plasma can be correlated with the size of the crystals (ii) absorption of the crystals in plasma can be correlated with the size of the crystals (iii) the particle size of the crystals can be controlled by crystal engineering and/or milling and (iv) the crystals are stable upon storage, and stable to sterilization procedures, such as gamma irradiation.
