Design and Characterization of Microemulsion Systems for Naproxen

Purpose: This research was aimed to formulate and characterize a microemolsion systems as a topical delivery system of naproxen for relief of symptoms of rheumatoid arthritis, osteoarthritis and treatment of dysmenorrheal. Methods: ME formulations prepared by mixing of appropriate amount of surfactant including Tween 80 and Span80, co-surfactant such as propylene glycol (PG) and oil phase including Labrafac PG –transcutol P (10:1 ratio). The prepared microemolsions were evaluated regarding their particle size, zeta potential, conductivity, stability, viscosity, differential scanningcalorimetry (DSC), scanning electron microscopy (SEM), refractory index (RI) and pH. Results: The mean droplets size of microemulsion formulation were in the range of 7.03 to 79.8 nm, and its refractory index (RI) and pH were 1.45 and 6.75, respectively. Viscosity range was 253.73- 802.63cps. Drug release profile showed that 26.15% of thedrug released in the first 24 hours of experiment. Also, Hexagonal and bicontinuous structures were seen in the SEM photograph of the microemulsions. Conclusion: characterization, physicochemical properties and in vitro release were dependent upon the contents of S/C ratio, water and, oil phase percentage in formulations. Also, ME-6 may be preferable for topical naproxen formulation.