Penetration Enhancers and Their Mechanism Studied on a Molecular Level

For the treatment of different skin diseases, the dermal application of drugs necessitates a temporary impairment of the skin’s very effective uppermost barrier, the stratum corneum, and more precisely the lipid matrix of this thin layer. As there is a high demand to improve the penetration of various substances into and through the skin, there is also the requirement to find suitable substances enhancing this process. Up to date there exist a variety of penetration enhancers, which are in use, but their exact mode of action on a molecule scale is often not understood. This chapter will review recent investigations to comprehend the mechanism of different penetration accelerators on a molecular level. Consequently, this chapter will concentrate first on hydrophilic penetration enhancers such as water, dimethyl sulfoxide, and urea, while in the second part, the focus is placed on unsaturated fatty acids such as oleic acid and pharmaceutically applied esters such as isopropyl myristate.