Complexation of Hydrocortison with β‐Cyclodextrin and Hydroxypropyl‐β‐Cyclodextrin

Hydrocortison (HC) forms water‐soluble inclusion compounds with β‐cyclodextrin (βCD) and hydroxypropyl‐β‐cyclodextrin (HPβCD), as proved by the equilibrium phase solubility diagrams and by 1 H‐NMR spectroscopy. The solubility isotherm of the HC/βCD system is of the B S type, that of the HPβCD system of the A L type. The values of the complex stability constants are K = 4792 M −1 and 1739 M −1 , respectively. 8 parallel preparations of solid HC/βCD complexes by coprecipitation resulted in a stoichiometric ratio of 0.49:1 which corresponds to a molar ratio of 1:2; the HC content is 13.2±0.2%. The ratio of the HC/HPßCD complex is 0.335 which equals a molar ratio of 1:3; the HC content is 8.6 ± 0.2%. The proof of inclusion formation was performed by X‐ray diffractometry and thermoanalytical procedures (DSC, TG, thermofractography). We cannot exclude that some of the HC molecules are not included in the HPßCD cavity.