Phase solubility and inclusion complex of itraconazole with β-cyclodextrin using supercritical carbon dioxide

Phase-solubility techniques were used to assess the formation of inclusion complex between itraconazole and beta-cyclodextrin. The stability constant and free energies of transfer of itraconazole from aqueous solution to the cavity of beta-cyclodextrin were calculated. Itraconazole solubility in supercritical carbon dioxide (SC CO2) was measured at different temperatures and pressures. Drug formulations of itraconazole were prepared by complexation of the drug into beta-cyclodextrin using SC CO2. Effects of temperature and pressure on inclusion yield of the prepared complexes were studied. The solvent-free inclusion complexes obtained from this method were characterized by UV spectroscopy, differential scanning calorimetry, powder X-ray diffraction, and scanning electron microscopy and compared to those obtained from physical mixing and coprecipitation methods. Results showed that beta-cyclodextrin significantly improved solubility of itraconazole in aqueous solutions. The free energies of transfer of itraconazole from aqueous solution to the cavity of beta-cyclodextrin increased negatively with increasing beta-cyclodextrin concentration. Higher inclusion yields were obtained in the SC CO2 method compared to physical mixing and coprecipitation methods. Both temperature and pressure had significant effects on itraconazole solubility in SC CO2 and the inclusion yield of the complex prepared by SC CO2 method. (C) 2005 Wiley-Liss, Inc. and the American Pharmacists Association.