Absorption of lidocaine and prilocaine after application of a eutectic mixture of local anesthetics (EMLA) on normal and diseased skin.

A eutectic mixture of 5% lidocaine and prilocaine was applied under occlusion for 1 or 2 hours on 25-100 cm2 areas of normal and diseased skin, and the absorption was followed by measuring the concentrations of the drugs in the draining vein and the general circulation at different time intervals after the application. The analgesic and vascular effects in the skin were also recorded. When the mixture was applied on normal skin the absorption was more rapid from the face than from the forearm. The absorption from diseased skin was faster than that from normal skin, with higher plasma concentrations, and a more rapid but shorter anesthetic effect was noted. With the doses used the plasma levels in the general circulation were 100 times lower than those associated with toxicity. The drug concentrations in the draining vein were highest after treatment of diseased skin and were 2-90 times higher than in the general circulation. The plasma concentrations of lidocaine and prilocaine ran parallel to each other, but the prilocaine level was 10-50% lower than that of lidocaine in the draining vein and 200-300% lower in the general circulation.