Transdermal drug delivery systems are gaining increasing interest due to their ability to bypass first-pass metabolism in the liver and provide better patient compliance while delivering drugs through a controlled-release mechanism. The outermost layer of human skin, known as the stratum corneum, creates a barrier to drug absorption that has proven challenging for water-soluble drugs and large molecules, including natural product compounds. The combination of nanoemulsion characteristics with hydrogel properties in nanoemulgels formulations serves as a novel method to enhance transdermal drug delivery. This review aims to evaluate the permeation efficacy of nanoemulgel systems in animal skin models. To do that, it evaluates nineteen studies examining how different skin structures affect drug permeation outcomes. Nanoemulgels formulations demonstrated superior results compared to traditional gels when combined with penetration enhancers such as clove oil or eucalyptus oil, according to the reviewed studies. These findings highlight the significance of model selection in permeation studies and demonstrate that nanoemulgels are promising vehicles for transdermal drug delivery. Animal skin permeation test results exhibit a similar pattern to those obtained from in vivo studies. However, differences in human skin make these results inapplicable to humans, requiring a thorough examination of differences between animal species.
Alfanura et al. (Wed,) studied this question.