Comparative study on the effects of the inclusion complexes of non-steroidal anti-inflammatory drugs with 2-hydroxypropyl-β-cyclodextrins on dissociation rates and supersaturation†

Active pharmaceutical ingredient (API) complexes with cyclodextrins (CDs) and their derivatives are widely formulated. Previously, we reported on the supersaturation effect and its benefits for CD inclusion complexes without polymers. The degree of amorphization and percentage of remaining crystals were determined using X-ray powder diffraction (XRPD) and differential scanning calorimetry (DSC) techniques. However, these properties clash with the stoichiometry of the solution according to the phase solubility diagram. In this study, the complexation contents of the prepared mixtures of indomethacin, piroxicam, diclofenac, and loxoprofen sodium with the 2-hydroxypropylated derivative of CD (HP-β-CD) were comparatively analyzed using dissolution curves. XRPD and DSC measurements indicated that equimolar mixtures were favorable for the interaction between these APIs and HP-β-CD. Enhancing the API solubility of HP-β-CD can be achieved through dissolution experiments. Mixtures of indomethacin with HP-β-CD consisted of an equimolar complex and corresponding remains. If the remaining component was HP-β-CD, then a gradual release of the equimolar complex was induced, and the release of diclofenac indicated similar dissolution behaviors. In contrast, the mixtures of indomethacin and diclofenac at molar ratios of 2 : 1 and 1 : 1 showed immediate supersaturation and a gradual decrease in the equilibrium concentration. These results indicate that the unbound HP-β-CD in the mixture acts as a matrix for controlled release.