Highly Concentrated Water-in-Oil Emulsions (Gel Emulsions)

Abstract

Emulsions represent an effective formulation approach for delivery of drugs and cosmetic agents. One of the most important applications of pharmaceutical emulsions is in skin therapy. Water-in-oil (W/O) emulsions have advantages in certain disease conditions related with dryness, where an emollient effect on the stratum corneum is required. They deposit a continuous lipid film as a protection barrier for the skin and generally provide occlusion. W/O highly concentrated emulsions constitute an interesting class of emulsions because of their large internal phase-volume fraction, their low surfactant content, and their unusual rheological and optical properties. In the spontaneous formation method, emulsification is achieved by a rapid temperature change of an oil-swollen micellar solution. It should be noted that the system is below the hydrophile-lipophile balance (HLB) temperature at the starting temperature and that emulsification takes place when it is rapidly heated above the HLB temperature.