A novel hydrogel-thickened microemulsion of dapsone for acne treatment: Development, characterization, physicochemical stability and ex vivo permeation studies

Acne vulgaris is a common inflammatory skin condition, which has been reclassified as a chronic disease. The spectrum of topical acne treatments has expanded substantially in recent years and various topical medications including topical dapsone are available. Dapsone has special physicochemical properties that make its topical formulation challenging. The aim of this study was preparing a hydrogelthickened microemulsion as a topical delivery system for dapsone. The microemulsions composed of dapsone (5%), isopropyl myristate, tween 80, diethylene glycol monoethyl ether, ethanol and water were prepared. The optimum microemulsion was modified with carbomer 940. Droplet size, pH, refractive index, conductivity, rheology of the optimized formulation, and skin permeation of dapsone through rat skin were evaluated. The optimized formulation significantly increased the skin permeation of dapsone in comparison to that of control gel. Although incorporation of menthol increased the particle size, the flux of microemulgel consisting of menthol (5%) was 2.51 times higher than that of the control. However, the skin absorption of the drug was less than 3%. Six month accelerated studies proved the physicochemical stability of microemulgels. The results of this research indicate that menthol based hydrogelthickened microemulsion system could be a promising vehicle for topical delivery of dapsone.