The Skin is one of the most extensive organs of the human body. This multilayered organ receives approximately one-third of all blood circulating through body. With a thickness of about a millimeter, the skin separates the underlying blood circulation network from the outside environment1.
Transdermal delivery of drugs through the skin to the systemic circulation provides a convenient route of administration for a variety of clinical indications. Transdermal delivery systems are currently available containing scopolamine (hyoscine) for motion sickness, clonidine and nitroglycerin for cardiovascular disease, fentanyl for chronic pain, nicotine to aid smoking cessation2.
Drug molecules in contact with the skin surface can penetrate by three potential pathways: through the sweat ducts, via the hair follicles and sebaceous glands (collectively called the shunt or appendageal route), or directly across the stratum corneum3.
All transdermal drug delivery systems consist mainly of:
- Polymer matrix
- Enhancers and other excipients