The objective of the present investigation was to develop and evaluate microemulsion based gel for the topical delivery of diclofenac sodium. The solubility of diclofenac sodium in oils, surfactants and cosurfactants was evaluated to identify components of microemulsion. The ternary diagram was plotted to identify the area of microemulsion existence. The 32 full experimental design was adopted to optimize the amount of Smix (mixture of surfactant and cosurfactant) (X1) and concentration of gelling agent (X2) in the microemulsion based gel. The formulations were assessed for % in-vitro drug release (Y1) and viscosity (cp) (Y2). The microemulsion containing 10% oil, 55% Smix, 35% water and 1.75% carbopol 980 was selected as optimized batch. The formulated microemulsion exhibits droplet size 192.2 nm, zeta potential -0.00856. The optimized microemulsion and microemulsion based gel was evaluated for their droplet size, zeta potential and physical appearance, pH, viscosity, globule size, drug content, spreadability, in-vitro and ex-vivo drug release, anti-inflammatory activity, stability study respectively. The formulated microemulsion exhibited droplet size 192.2 nm, zeta potential -0.00856 and optimized gel formulation appear as milky white, exhibits globule size 411.5 nm, pH 6.39±0.8, viscosity 14194 cp, % drug release 91.87±1.3, % drug content 98.23±1.2 respectively. The optimized microemulsion based gel did not show any signs skin irritation and exhibits anti-inflammatory study as effective as marketed gel (Voveron gel). In conclusion the microemulsion based gel may be used as an alternative for the transdermal delivery of diclofenac sodium.
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