Comparison of the potency of lidocaine and chloroprocaine in sciatic nerve block in Sprague-Dawley rats.
OBJECTIVE
This study investigates the relative potencies and ED(50) of the local anesthetics lidocaine and chloroprocaine in a sciatic block in Sprague-Dawley rats.


METHODS
The study involved 80 rats (chloroprocaine n = 40, lidocaine n = 40). Each rat was injected close to the sciatic nerve with 0.1 ml of the concentration of local anesthetic being tested. Using the up-and-down allocation technique, the next concentration was determined by the response of the previous subject to a higher or lower concentration. A successful block was assessed by pinching the fifth metatarsal. Absent vocalization and a very weak withdrawal response were defined as the onset of block.


RESULTS
Using the up-and-down methodology, the estimates of ED(50) for chloroprocaine was 0.1 ml of 1.2% (with 95% CI of 1.1-1.6), and that for lidocaine was 0.1 ml of 0.65% (with 95% CI of 0.65-0.88), giving a lidocaine/chloroprocaine potency ratio of 1.85 (with 95% CI of 1.66-2.61).


CONCLUSIONS
Using the results of this study, the effects of the two drugs can be compared using the commercially available concentrations of chloroprocaine and lidocaine in a peripheral nerve block.
Department of Anesthesiology, New York Methodist Hospital, Brooklyn, NY 11215, USA.
Elliot
E
Yung
Joel M
JM
Yarmush
Jonathan
J
Weinberg
Joseph J
JJ
SchianodiCola
Sidhartha D
SD
Ray
D000779:Anesthetics, Local / Q000008:administration & dosage / Q000494:pharmacology*; D000818:Animals; D004305:Dose-Response Relationship, Drug; D008012:Lidocaine / Q000008:administration & dosage / Q000494:pharmacology*; D008297:Male; D009407:Nerve Block; D011343:Procaine / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000494:pharmacology; D011897:Random Allocation; D051381:Rats; D017207:Rats, Sprague-Dawley; D012584:Sciatic Nerve / Q000187:drug effects*
D000779:Anesthetics, Local; D011343:Procaine; C004616:chloroprocaine; D008012:Lidocaine