ABSTRACT
Human skin, the largest single organ of the body (up to 16% of body weight), provides the formulator with a wide and easily accessible area for drug application. It is a complex, layered structure, forming a barrier between the body and the outside environment. The percutaneous route for drug administration has many advantages over other pathways, including avoidance of gut and hepatic first pass effects, continuous drug delivery, fewer side effects, and improved patient compliance. Unfortunately, the protective function of the skin makes it difficult for most drugs to penetrate into and through the skin. The outermost layer of the skin (stratum corneum) provides the principal barrier to permeation and consists of corneocytes embedded in a highly organized lipid matrix. Several approaches have been developed to disorganize the lipid bilayers, thereby enhancing the penetration of drugs (1).
