Journal of

Transdermal drug delivery (TDD) is a non-invasive, topical administration method for therapeutic agents. Transdermal delivery also has advantages including providing release for long periods of time, improving patient compliance, and generally being inexpensive. Despite these advantages, the use of TDD has been limited by innate barrier functions of the skin. Only small (<500 Da), lipophilic molecules can passively diffuse through the skin. As a result of the barrier function of the skin, passive transdermal delivery has primarily been limited to small molecules. The skin, which consists of several layers including the stratum corneum, other epidermal layers, and dermis, is the primary defense system of the body. The main barrier to therapeutic delivery is the outermost layer of the skin, the stratum corneum. As a result, various methods of skin permeabilization have been explored for their ability to enhance the transport of drugs across the stratum corneum. Scientists evaluated new drug delivery systems such as nano-carriers and drug delivery systems and enhancer methods such as penetration enhancers. The purpose of drug delivery systems are to deliver sufficient drug molecules into the skin with maximum stability and minimal toxicity. To guarantee successful transdermal drug delivery, a drug delivery system must exhibit several essential properties including drug protection, targeted drug delivery, biocompatibility and biodegradability.

This paper reviews transdermal drug delivery systems, recent enhancement techniques to optimize drug delivery such as microneedles and especially vesicular systems.  Herein, we focus on the differences in their composition, physico-chemical properties and applications of those drug delivery systems. We hope recent innovations can work as a foundation for further research and development in transdermal drug delivery system.