Properties of Solid Dispersions of Naproxen in Various Polyethylene Glycols

Solid dispersions of naproxen in polyethylene glycol 4000, 6000, and 20000, aimed at improving the drug dissolution characteristics, were prepared by both the solvent and melting methods. The drug-polymer interaction in the solid state was investigated using differential scanning calorimetry, hot-stage microscopy, Fourier-transform infrared spectroscopy, and x-ray diffraction analysis. Interaction in solution was studied by phase solubility analysis and dissolution experiments. Computer-aided molecular modeling was used to supplement the results from phase solubility studies. No important chemical interaction was found between naproxen and polyethylene glycol, either in solution or in the solid state, apart from the formation of weak drug-polymer hydrogen bonds. The increase of naproxen dissolution rate from its binary systems with polyethylene glycol could be attributed to several factors such as improved wettability, local solubilization, and drug particle size reduction. No influence of polymer molecular weight or of the solid dispersion preparation method on drug dissolution properties was found.