Thermal behaviour and dissolution properties of naproxen in combinations with chemically modified ß-Cyclodextrins

Binary systems of naproxen with statistically-alkylated ßcyclodextrins (methyl, hydroxyethyl and hydroxypropyl derivatives) were investigated for both solid phase characterization (differential scanning calorimetry, X-ray powder diffraction) and dissolution properties (dispersed amount and rotating disc methods). Kneading, coevaporation and colyophilization of the 1:1 (mol/mol) naproxen/methyl ßcyclodextrin combination, as well as colyophilization of analogous combinations of naproxen with hydroxyethyl and hydroxypropyl ßcyclodextrin, led to amorphous products with higher dissolution rates than the corresponding physical mixtures. A conversion of crystalline to amorphous naproxen was also observed by heating the physical mixtures at about 393 K. The amorphous statistically-alkylated ßcyclodextrins, in particular methyl ßcyclodextrin, can be employed as amorphizing agents for crystalline naproxen.