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. Pinprick sensation was tested every 15 min for 6 h.


RESULTS
Median time to return of normal sensation was 3.5 h for lidocaine alone, but at least 6 h if combined with clonidine (P < 0.001).


CONCLUSIONS
Clonidine has a significant peripheral action in enhancing duration of local anesthesia on superficial co-infiltration with lidocaine.
Pratap
Jayant Nick
JN
Department of Anaesthesia, Guy's & St. Thomas' NHS Foundation Trust, London, UK.
Shankar
Rajesh K
RK
Goroszeniuk
Teodor
T
D000316:Adrenergic alpha-Agonists / Q000008:administration & dosage / Q000494:pharmacology*; D000779:Anesthetics, Local / Q000008:administration & dosage / Q000494:pharmacology*; D003000:Clonidine / Q000008:administration & dosage / Q000494:pharmacology*; D004311:Double-Blind Method; D004338:Drug Combinations; D005542:Forearm; D006801:Humans; D007279:Injections, Subcutaneous; D008012:Lidocaine / Q000008:administration & dosage / Q000494:pharmacology*; D009407:Nerve Block; D017288:Pain Threshold / Q000187:drug effects*; D012016:Reference Values; D012867:Skin / Q000294:innervation*; D013997:Time Factors
D000316:Adrenergic alpha-Agonists; D000779:Anesthetics, Local; D004338:Drug Combinations; D008012:Lidocaine; D003000:Clonidine