In the present study, we investigated the complexation of risperidone with hydroxypropyl-β-cyclodextrin （HP-β-CD） in aqueous solution due to the poor water solubility and low oral bioavailability of risperidone in humans. The effect of temperature on the complexation was examined, and thermodynamic parameters of the complexation process, such as Gibbs free energy change （AG）, enthalpy change （AH） and entropy change （AS）, were also explored. Meantime, the solid dispersion of risperidone with HP-β-CD was prepared and confirmed by Fourier IR spectroscopy and X-ray diffractometry. The experimental results suggested that the complex of the drug with HP-β-CD at a molar ratio of 1：1 could form in aqueous solution, and the complexation was an endothermic and entropy-driven process. The risperidone-HP-β-CD solid dispersion exhibited a remarkable improvement in the dissolution rate of the drug. This might be attributed to the amorphous state, the enhanced wettability as well as the complex formation of the drug with HP-β-CD in aqueous solution.
