Mechanisms of Transdermal Drug Delivery

The use of the skin as a route of delivery into the systemic circulation has been exploited since the 1950s with the development of ointments containing agents such as nitroglycerin and salicylates. This has been extended since the early 1980s to hormone replacement therapy with the development of skin patches and gels. The skin affords a major barrier and the mechanisms of drug transport across it are discussed. Delivery of oestradiol and progestogens are discussed.