Study of the inclusion complexes of γ-cyclodextrin with non-steroidal anti-inflammatory drugs using differential scanning calorimetry

The formation of cyclodextrin clathrates with NSAIDs leads to an improvement in their physicochemical properties. To confirm the structure of the inclusion complex, a combination of physicochemical analysis methods was used, including differential scanning calorimetry (DSC).

To obtain the clathrate, γ-cyclodextrin (γ-CD) and the NSAID nimesulide, which is used in the treatment of acute and chronic pain, were employed. The possibility of complex formation was previously evaluated using the ChemOffice 16.0 and Gaussian 09W software packages. Complexation was achieved through co-precipitation and co-evaporation methods. Changes in the thermal properties of the obtained complexes were recorded by the DSC method.

During the study, thermograms and thermodynamic characteristics of γ-CD, nimesulide, and the proposed complexes were obtained. The shift of the endothermic peak of nimesulide (from 148°C to 191°C), corresponding to its melting point, indicates its possible incorporation into the γ-CD cavity and transition to an amorphous state. The endothermic peak of γ-CD at around 75°C decreases in intensity due to the expected change in hydration during complexation. The appearance of an endothermic peak near 283°C may correspond to the decomposition of the complex or a change in its structure.

Thus, the DSC study confirms the formation of an inclusion complex between γ-CD and nimesulide, and the data are consistent with the results of computer modeling, indicating the possibility of successful complexation.