Innovative Strategies for Enhancing Topical and Transdermal Drug Delivery

Historically, the skin was thought to be a simple homogenous barrier. However, it is now known to be a highly specialised organ, and plays a key role in homeostasis. The protective properties of the skin are provided by the outermost layer, the epidermis, which safeguards against chemical, microbial, and physical attack. The exceptional barrier properties of the skin result in it being a challenging route for the delivery of therapeutic agents. This article reviews strategies developed to enhance the skin penetration of drugs, ranging from conventional approaches, for example the use of chemical penetration enhancers to those in early-stage development, such as microscissioning.