The aim of the present investigation was to develop and characterize naproxen sodium loaded microemulsion based gel (MEBG) for treatment of rheumatoid arthritis. Screening of components was based on the drug solubility, HLB value and biocompatibility. Pseudo-ternary phase diagrams were constructed at different surfactant to co-surfactant ratios to identify the microemulsion (ME) existing zone. MEs were formulated by water titration method, optimized and characterized. Optimized ME was then formulated into MEBG by adding carbopol 934P as a gelling agent and was characterized. Comparative in-vitro drug release of formulations was studied for 12 hr and data fitted to different release kinetic models. Three months stability study was conducted as per ICH guidelines. % transmittance, globule size, zeta potential and drug content of optimized ME containing oleic acid as oil, tween-80 as surfactant and isopropyl alcohol as co-surfactant were found to be 99.8±0.2%, 16.62±3.5 nm, -24.3±1.66 mV and 99.03±0.35% respectively. Drug permeation data fit well to higuchi equation plot (r2 = 0.930) indicating the diffusion rate limited drug permeation from developed formulation. Drug permeation mechanism was found as a super case-II transport (i.e., n value- 1.504). Developed ME was transparent, stable up to 2 months with nano particle size. Hence, developed microemulsion formulations of Naproxen sodium is considered to be safe for topical delivery to treat rheumatoid arthritis.
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