An improved system using both supercritical antisolvent precipitation and rapid expansion from supercritical to aqueous solution (RESAS) was proposed to overcome the problem of low solubility of medicinal substances in scCO 2 . When the ethanol solution with IMC was sprayed into the vessel purged with scCO 2 , no precipitation of IMC was observed if the CO 2 pressure was more than 15MPa at 40°C. This indicates that very small droplets of the ethanol solution with IMC could disperse in the high pressure CO 2 . After expansion into distilled water using an RESAS device, this same solution, in CO 2 at high pressure, produced submicron particles of IMC. For the pharmaceutical application, the IMC suspension was freeze-dried and re-dispersed to the aqueous media. SEM images of freeze-dried sample showed that the suspension was composed of submicron particles with 300–500nm. Although the average particle size of re-dispersed IMC related significantly to the pressure and temperature in the vessel on scCO 2 processing, the freeze-dried sample of the IMC suspension after the treatment shows good redispersibility as a nanosuspension. This apparatus is found to be a promising way to produce fine crystals of IMC with a high yield.