Co-injection of clonidine prolongs the anesthetic effect of lidocaine skin infiltration by a peripheral action.

Background: The addition of clonidine to local anesthesia prolongs the local anesthetic action, but in humans, the contribution of a peripheral mechanism remains unclear.

Methods: We investigated clonidine's peripheral effect in 20 healthy volunteers undergoing double-blind, subcutaneous infiltration of 0.5% lidocaine with normal saline to one forearm and then, immediately, of lidocaine with 10 mug clonidine to the contralateral arm.