Formulation Optimization of Topical Gel Formulation Containing Micro-emulsion of Terbinafine Hydrochloride with Simplex Lattice Design

The aim of the present investigation was to evaluate the potential application of microemulsions in topical drug delivery loading terbinafine hydrochloride. The pseudo-ternary phase diagrams were developed for various microemulsion formulations composed of cottonseed oil (oil phase), Tween 80 (surfactant) and ethanol (cosurfactant). Composition of microemulsion systems was optimized using simplex lattice design including the concentrations of surfactant, cosurfactant and water (independent variables) and the amount of drug released in first hour and t50% (response variables). The physicochemical properties of the optimized microemulsion, microemulsions incorporated into1% carbopol 974P gel base and the invitro drug diffusin of terbinafine hydrochloride from the gels prepared with microemulsions were also investigated. The results showed that the optimized microemusion formulation was composed of cottonseed oil (10%, w/w), Tween 80 (15%,w/w), ethanol (30%, w/w) and water (45%, w/w). The mean globule diameter was 65.56 nm. The conclusion was that the release controlling ability of microemulsion containing gel formulations was significantly improved in comparison to commercial cream.