Transdermal drug delivery in pain management

Abstract

Transdermal drug delivery is defined as the non-invasive delivery of medications through the skin surface. The use of analgesics as a ‘pain relief patch’ is gaining popularity. When applied to the skin, these patches can deliver an analgesic drug at a predetermined rate across the dermis to achieve either a local or systemic effect. Transdermal delivery of medications is not a new concept. The use of transdermal delivery of homemade medicinal preparations dates to the early 20th century. Mustard plasters were used for severe chest congestion. The Belladonna Plaster, containing 0.25% of Belladonna alkaloid, had a place in the US pharmacopeia as a transdermal analgesic. The success of nicotine patches nearly two decades ago revolutionized the use of transdermal drug delivery. Over the last decade, an increasing number of analgesic drugs have become available as transdermal patches. Patches offer advantages over conventional parenteral or oral routes. They ensure controlled absorption and more uniform plasma drug concentrations. Bioavailability is improved by avoiding first-pass hepatic metabolism and enzymatic or pH-associated deactivation. Delivery of the drug is via a simple and painless application. There is increased flexibility in terminating drug administration by patch removal. Patient compliance is improved as patches are simple, non-invasive, and convenient. Clear labelling ensures rapid identification of medication. There are, however, some limitations to transdermal drug delivery. First, there may be local irritation or sensitization of the skin at the site of patch application. Secondly, not all drugs are suitable for transdermal delivery. Thirdly, this modality is not suitable for shocked patients as decreased peripheral blood flow leads to unreliable transdermal absorption. Finally, in comparison with other routes of drug delivery, the transdermal route is relatively more expensive.