Delivery of adapalene using a novel topical gel based on tea tree oil nano-emulsion: Permeation, antibacterial and safety assessments.

The aim of present study was to design and optimize 0.1% adapalene loaded nano-emulsion to improve the drug efficacy and increase its user compliance. Effect of type and concentration of surfactants was studied on size of 0.1% adapalene loaded nano-emulsion. Optimized formulation was then evaluated for particle size, polydispersity index, morphology, viscosity, and pH. Subsequently, 1% carbopol® 934 was incorporated to the optimized formulation for preparation of its gel form. The efficacy and safety of 0.1% adapalene loaded nano-emulsion gel was assessed compared to marketed gel containing 0.1% adapalene. In-vitro studies showed that adapalene permeation through the skin was negligible in both adapalene loaded nano-emulsion gel and adapalene marketed gel. Furthermore, drug distribution studies in skin indicated higher retention of adapalene in the dermis in adapalene loaded nano-emulsion gel compared with adapalene marketed gel. Antibacterial activity against Propionibacterium acnes showed that adapalene loaded nano-emulsion is effective in reducing minimum inhibitory concentration of the formulation in comparison with tea tree oil nano-emulsion, and pure tea tree oil. In vivo skin irritation studies showed absence of irritancy for adapalene loaded nano-emulsion gel. Also, blood and liver absorption of the drug, histological analysis of liver and liver enzyme activity of rats after 90 days' treatment were investigated. No drug was detected in blood/liver which in addition to an absence of any adverse effect on liver and enzymes showed the potential of adapalene loaded nano-emulsion gel as a novel carrier for topical delivery of adapalene.