PHYSICOCHEMICAL AND RELEASE STUDIES OF NAPROXEN IN POLOXAMER GELS

The solubility of naproxen at pH 2 was significantly increased as a li near function of PF-127 concentration at three temperatures. Naproxen was highly entrapped by the micelles as indicated by large partition c oefficients. The micellar solubilization was a spontaneous (Delta G < 0) and exothermic (Delta H < 0) process which resulted in a less order ly state (Delta S > 0). In the presence of PF-127, the release of napr oxen across the membrane was significantly sustained at pH 2 and inver sely proportional to the surfactant concentration. At pH 7, PF-127 had little effect on the membrane transport of naproxen. The release of n aproxen from the PF-127 gel into isopropyl myristate was dependent on the medium pH. The highest release was observed at pH 6.3. The diffusi on coefficients of naproxen were inversely proportional to drug loadin g and PF-127 concentration. The activation energy of 7.45 kcal/mol for the diffusion of naproxen in the gel was calculated using the Arrheni us equation.