Development and optimization of sulfasalazine loaded microemulsion for improved topical treatment of psoriasis

Psoriasis is a persistent, chronic autoimmune skin disease that affects around 2% of the global population. Conventional therapies often exhibit limited efficacy, systemic side effects, and poor patient compliance due to long-term treatment needs.

This study focused to develop and optimize a sulfasalazine-loaded microemulsion (SSZ-ME) for topical delivery to enhance skin penetration and therapeutic efficacy in psoriasis. Pseudo-ternary phase diagrams were prepared to identify the optimal surfactant mixture, with Tween 80 and Polyethylene Glycol 400 selected in a 2:1 ratio. A 2³ factorial design was used to optimize formulation parameters, focusing on oil and surfactant mixture effects on globule size and viscosity.

The resulting microemulsions showed globule sizes between 60 ± 0.42 to 349 ± 0.13 nm, with optimal viscosity. In vitro release studies confirmed sustained drug release over 24 hours, following first-order kinetics. Skin permeation studies demonstrated enhanced drug penetration with SSZ-ME, while histopathological analysis revealed significant improvements in psoriatic symptoms in mice treated with 4% SSZ-ME compared to 2% SSZ-ME and marketed formulation. Blood analysis confirmed minimal systemic absorption and localized action. These results suggest that SSZ-ME offers a promising, patient-compliant, and effective topical therapy for psoriasis with improved therapeutic outcomes and minimal systemic exposure.