Nisoldipine dissolution profile enhancement by supercritical carbon dioxide impregnation technique with fumed silica

The purpose of this study is to improve the dissolution rate of nisoldipine (NSD) by adsorbing it onto fumed silica employing a supercritical CO2 (scCO(2)) impregnation technique. NSD-fumed silica formulations were prepared using scCO(2) and ethanol as solvent (NSD-fumed silica scCO(2) and NSD-fumed silica ethanol) respectively. The characteristics of both formulations were confirmed by X-ray diffraction, infrared spectroscopy, scanning electron microscopy, specific surface area, and differential scanning calorimetry, which indicated that NSD was present in the amorphous state. The results of the stability tests showed that the NSD-fumed silica ethanol started to recrystallize under the humid conditions (RH 92.5 +/- 5%), while this phenomenon was not seen with NSD-fumed silica scCO(2). In the dissolution tests, NSD from NSD-fumed silica scCO(2) was further released compared with that from pure NSD and NSD-fumed silica ethanol in 8 different kinds of dissolution media. These results suggest that the method of using scCO(2) as the solvent is suitable for enhancing the dissolution rate and stability, and it did not require toxic solvents. (C) 2014 Elsevier B.V. All rights reserved.