Nano emulsion is one of the most successful strategies for transdermal drug delivery and offers many advantages, such as higher storage stability, lower preparation costs, good manufacturing feasibility, thermodynamic stability, lack of organic solvents and no need for intensive sonication. When compared to emulsions, nano emulsions do not show any stability problems such as creaming, flocculation, coalescence, and sedimentation and has better appearance and consistency because of nano size range. Drug to be delivered topically is incorporated into oil phase and then incorporated in water phase along with surfactant/co-surfactant. After primary emulsion is formed the particle size is reduced by low energy process or high energy methods. It was observed that nano emulsions are better than emulsions or micro emulsions because of better stability and appearance and also shows good permeation and retention ability. This review focuses on nano emulsions including its properties, mechanism of action and formulation considerations with characterization parameters to study the effectiveness in drug delivery.

Keywords: Nano emulsion, transdermal drug delivery, mechanism of action, formulation, characterization.