PUBLISHED: 12:12 PM on Wednesday, January 4, 2006
Heat Can Increase Drug Absorption from a Patch
An increase in skin blood flow during heat exposure can dramatically alter the absorption of drugs which are administered using a patch. Transdermal absorption of drugs is regulated by skin permeability and local blood flow and can be dangerously increased by heat, which increases blood flow and blood vessel permeability.

A rise in temperature may also increase drug solubility both in the patch formulation and within the skin, increasing the rate of drug release. For example, a fever of 104?F can potentially increase levels of the analgesic found in Duragesic patches by one-third, and shorten the duration of the patch from three days to two. Package inserts warn patients to avoid exposing the application site to direct external heat sources, such as heating pads, hot tubs, heated water beds, etc., while wearing the patch.

One study indicated that absorption of hormones from the contraceptive patch Ortho Evra was not altered under conditions of heat, humidity, and exercise. In contrast to a patch, when a patient uses a transdermal cream or gel, the total amount of medication contained in the dose is much less than that in a patch, reducing the risk of toxicity from excessive drug exposure. Ask our compounding pharmacist for more info.