Development and Characterization of topical microemulsion as novel drug delivery system for Dapsone

Dapsone is a Biopharmaceutical Classification System class II drug with anti inflammatory, immunosuppressive, antibacterial, and antibiotic properties and is  used as an antileprotic. The purpose of the present study was to investigate the  potential of a microemulsion formulation for topical delivery of dapsone to enhance  permeation and to avoid systemic side effects. When administered orally, dapsone  undergoes hepatic metabolism. Its hepatic metabolite, dapsone hydroxylamine,  shows systemic side effects such as hemolytic anaemia peripheral neuropathy,  nausea, and headache. A novel drug delivery system in the form of a microemulsion  was developed for dapsone. This is the first attempt that dapsone has been  combined with chaulmoogra oil in a topical microemulsion. The primary drugs used  for the treatment of leprosy are found in chaulmoogra seeds. Considering its good  solubilizing capacity and its use in the treatment of leprosy, chaulmoogra oil was  chosen as the oil phase. Based on emulsification ability, Cremophor RH40 and PEG  400 were selected as surfactant and co-surfactant, respectively. A pseudo-ternary  phase diagram was constructed to identify the microemulsion region. Smix  (Cremophor RH40: PEG-400 in the ratio of 1:2) was most effective in imparting  stability to the formulation. The selected formulation exhibited appropriate  diffusion behavior (in vitro). The developed dapsone containing microemulsion  formulation exhibited the optimal homogeneity, clarity, pH, type of microemulsion,  viscosity, percent drug content, and percent transmittance to qualify as a topical  drug delivery system for local treatment of leprosy.