Nimesulide and β-cyclodextrin inclusion complexes:: Physicochemical characterization and dissolution rate studies

Complex formation of nimesulide (N) and beta -cyclodextrin (beta CD) in aqueous solution and in solid state and the possibility of improving the solubility and dissolution rate of nimesulide via complexation with beta CD were investigated. Phase solubility studies indicated the formation of a 1:1 complex in solution. The value of the apparent stability constant Kc was 158.98 M-1. Solid inclusion complexes of N and beta CD were prepared by kneading and coevaporation methods. Differential scanning calorimetry (DSC) studies indicated the formation of solid inclusion complexes of N-beta CD at a 1:2 molar ratio in both the methods. Solid complexes of N-betaD (1:1 and 1:2 M) exhibited higher rates of dissolution and dissolution efficiency values than the corresponding physical mixtures and pure drug. Higher dissolution rates were observed with kneaded complexes than with those prepared by coevaporation. Increases of 25.6- and 38.7-fold in the dissolution rate were observed, respectively, with N-beta CD 1:1 and 1:2 kneaded complexes.