Physico-chemical studies of inclusion complex between hydrocortisone and cyclodextrins

Hydrocortisone (HC) is widely utilized in the pharmaceutical field for various administration routes, including oral, parenteral, and topical routes. However, its application in ocular disease treatment as a solution is limited due to its poor aqueous solubility. To address this limitation, in this study we aimed to investigate different types of cyclodextrins (CDs) to identify the most effective CD for improving the inherent solubility of HC. Results from scanning electron microscopy, rheology and differential scanning calorimetry (DSC) demonstrated the formation of inclusion complexes, while isothermal titration calorimetry (ITC) investigations accurately determined the thermodynamic parameters associated with the formation of complexes between HC and HPβCD or βCD, at 25 and 37 °C. Additionally, phase solubility studies in PBS buffer at 37 °C confirmed the formation of stable inclusion complexes. Collectively, results indicated that HPβCD was the most effective CD in enhancing the intrinsic solubility of HCs in PBS highlighting its potential for improving the solubility and formulation of HC-based pharmaceutical products.