Dextromethorphan or dextrorphan have a local anesthetic effect on infiltrative cutaneous analgesia in rats.
BACKGROUND
Dextromethorphan blocks sodium channels, the site of action of local anesthetics. In this study we evaluated whether dextromethorphan has a local anesthetic effect.


METHODS
We administered dextromethorphan and its active metabolite--dextrorphan, and lidocaine subcutaneously to rats and tested them for cutaneous anesthesia. Drug-drug interactions and systemic safety indices (LD50s/ED50s) were also evaluated.


RESULTS
Dextromethorphan and dextrorphan had a local anesthetic effect after cutaneous infiltration. The ranking of potencies was dextromethorphan > dextrorphan > lidocaine (P < 0.01 for each comparison). A combination of dextromethorphan or dextrorphan with lidocaine produced an additive effect. Dextromethorphan and dextrorphan had 2.4- and 1.9-fold higher system safety indices than did lidocaine.


CONCLUSIONS
Dextromethorphan and dextrorphan were more potent local anesthetics than lidocaine, but with higher systemic safety indices. Coadministration of dextromethorphan or dextrorphan with lidocaine produced an additive effect.
Chen
Yu-Wen
YW
Department of Medical Research, Chi-Mei Medical Center, Tainan, Taiwan.
Chu
Koung-Shing
KS
Lin
Ching-Nan
CN
Tzeng
Jann-Inn
JI
Chu
Chin-Chen
CC
Lin
Mao-Tsun
MT
Wang
Jhi-Joung
JJ
D000698:Analgesia / Q000379:methods*; D000779:Anesthetics, Local / Q000008:administration & dosage*; D000818:Animals; D003915:Dextromethorphan / Q000008:administration & dosage*; D003917:Dextrorphan / Q000008:administration & dosage*; D004305:Dose-Response Relationship, Drug; D007279:Injections, Subcutaneous; D007928:Lethal Dose 50; D008012:Lidocaine / Q000008:administration & dosage; D008297:Male; D010147:Pain Measurement / Q000187:drug effects / Q000379:methods; D051381:Rats; D017207:Rats, Sprague-Dawley
D000779:Anesthetics, Local; D003917:Dextrorphan; D003915:Dextromethorphan; D008012:Lidocaine