Research Summary:
It has been recognized that the vehicle in which a permeant is applied to the skin has a distinctive effect on the dermal and transdermal delivery of active ingredients. The cutaneous and percutaneous absorptions can be enhanced, for example, by an increase in thermodynamic activity, supersaturation, and penetration modifiers. Furthermore, dermal and transdermal delivery can be influenced by the interactions that may occur between the vehicle and the skin on the one hand, and interactions between the active ingredient and the skin on the other hand.
Emulsions are widely used as cosmetic and pharmaceutical formulations because of their excellent solubilizing capacities for lipophilic and hydrophilic active ingredients and application acceptability. This review focuses, in particular, on the effect of emulsions on the dermal and transdermal delivery of active ingredients.
It is shown that the type of emulsion (water-in-oil vs. oil-in-water emulsion), the droplet size, the emollient, the emulsifier, as well as the surfactant organization (micelles, lyotropic liquid crystals) in the emulsion, may affect the cutaneous and percutaneous absorption. Examples substantiate the fact that emulsion constituents such as emollients and emulsifiers should be selected carefully for optimal efficiency of the formulation.
Moreover, to understand the influence of emulsion on dermal and transdermal delivery, the physicochemical properties of the formulation after application are considered.
Keywords: dermal and transdermal delivery, emulsifier, emulsion, skin, vehicle effect.
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