Delivery of medication through the skin, as with a patch, gel, or spray.
Also known as: through the skin
Transdermal delivery means a medication is absorbed through the skin rather than swallowed, using a patch, gel, or spray. This route bypasses the first pass through the liver.
For estrogen therapy, the transdermal route is often discussed because it delivers hormone directly into the bloodstream; the choice of route is made with a clinician.