Enhanced dissolution and oral bioavailability of coenzyme Q10 in dogs obtained by inclusion complexation with γ-cyclodextrin

Purpose: The solubility of coenzyme Q10 (CoQ10) in water is extremely low, resulting in a low oral bioavailability. In this study, we attempted to improve the low dissolution and bioavailability of CoQ10, by means of the complexation with natural α-, βand γ-cyclodextrins (CyDs) and 2-hydroxypropyl-β-CyD (HP-β-CyD). Methods: The complexation of CoQ10 with CyDs was studied by the solubility method. Solid CoQ10/CyD complexes with different molar ratios were prepared by the kneading method using ethanol/water (1: 1) mixed solvent. Results: Among these CyDs, γ-CyD signifi cantly increased the solubility of CoQ10 at lower CyD concentrations. The powder X-ray diffraction peaks of CoQ10 disappeared following solid complexation with γ-CyD, although the endothermic peak due to the melting of the drug did not disappear completely. The dissolution rate of CoQ10 was signifi cantly increased by complexation with γ-CyD, probably due to soluble complex formation and/or nanometer-sized particle formation, which was refl ected in the enhanced oral absorption in dogs. Conclusion: The results indicated that γ-CyD is useful for improving the oral bioavailability of CoQ10.