ABSTRACT
A large variety of oils, surfactants, cosurfactants, and aqueous phases are available to obtain microemulsions. The percentage (or ratio) of the different components, as well as the interaction between them, should be insightfully controlled due to their capacity to induce alterations in microemulsion properties, namely structure, electric conductivity, viscosity, and drug solubilization. Microemulsions are endowed of a small droplet size and the capacity of solubilizing lipophilic and hydrophilic drugs, allowing for a superior drug accumulation in the active site. These drug delivery systems act as penetration enhancers, due to the presence of surfactants and oily components, increasing the transdermal absorption of the drug. The addition of a cosurfactant to the surfactant mixture enhances this effect synergistically. Nevertheless, some of the components in microemulsions, particularly, surfactants, cosurfactants, and oily components, may be responsible for the occurrence of skin irritation reactions and comedogenic effects, although these adverse effects can be minimized. Currently, the search worldwide for new drug delivery systems is one of the greatest scientific purposes. Current technological developments enable the improvement and the production of new and advanced analytical devices. Improvements in the analytical 92devices allow consequently for a more efficient and reliable characterization of microemulsions. Furthermore, to maximize clinical and cosmetic potentials of microemulsions, not only the characterization of the formulations but also the safety concerns must be addressed during the optimization process.
