Formulation and In Vitro Evaluation of Topical Emulgel Containing Combination of a Local Anaesthetic and an Anti-Inflammatory Drug

An emulgel formulation was developed for a local anesthetic agent (pramoxine hydrochloride) and a topical steroidal anti-inflammatory agent (prednicarbate) in combination, using sepigel as the gelling agent. The effect of concentrations of oil, surfactant and gelling agent on the in vitro drug release pattern was investigated using 2(3) factorial design. To avoid interference of the peaks of both the drugs in normal UV spectra, second order derivative spectrophotometric method was developed for the evaluation of formulation drug content and analysis of drugs released from the formulations. The optimized emulgel formulations were characterized for appearance, color, pH, homogeneity, viscosity and spreadability. The rheological property of emulgels showed shear thinning behaviour with thixotropy. The in vitro release profiles of both the drugs from the emulgel formulation were strongly affected by the concentration of gelling agent, surfactants and oil. The drug release from the optimized emulgel formulation was found to follow the diffusion controlled Higuchi model. Stability studies were conducted at different temperatures and humidity conditions that indicated the formulations to be stable under accelerated conditions. No erythema or irritation was observed during the skin irritation studies on rabbits. The results obtained can be considered as a step forward for the prolonged topical delivery of drugs in combination for the treatment of various skin disorders.