Clonidine intensifies memantine cutaneous analgesia in response to local skin noxious pinprick in the rat.
BACKGROUND
The purposes of this study were to evaluate the co-administration of clonidine with memantine and to determine whether it has a peripheral action in intensifying cutaneous analgesia.


METHODS
Cutaneous analgesia was examined through inhibition of the cutaneous trunci muscle reflex in response to the local noxious pinprick in rats. Effect of the added subcutaneous clonidine to memantine on infiltrative cutaneous analgesia was assessed and compared with the local anesthetic lidocaine.


RESULTS
On the 50% effective dose (ED50) basis, the rank of drug potency was memantine [4.05 (3.95-4.18) μmol]>lidocaine [5.81 (5.70-5.98) μmol] (p<0.01). Clonidine at a dose of 0.12 μmol did not elicit cutaneous analgesia. Mixtures of clonidine (0.12 μmol) with drug (memantine or lidocaine) at ED50 or ED95 prolonged the duration of action and enhanced the potency as infiltrative cutaneous analgesia. Clonidine enhanced the lidocaine cutaneous analgesia in which had a better effect than added to memantine.


CONCLUSIONS
Our resulting data showed that memantine displayed more potent cutaneous analgesia than lidocaine. Co-administration of memantine or lidocaine with clonidine increased the potency and duration of the cutaneous analgesia. Clonidine intensified the effects of lidocaine promoting cutaneous analgesia than added to memantine.
Department of Physical Therapy, Graduate Institute of Rehabilitation Science, China Medical University, Taichung, Taiwan.
Bor-Tsang
BT
Wu
Department of Anesthesiology, Chi Mei Medical Center, Tainan, Taiwan.
Kuan-Ting
KT
Chen
Department of Pharmacy, Chia Nan University of Pharmacy and Science, Tainan, Taiwan.
Kuo-Sheng
KS
Liu
Department of Physical Therapy, Graduate Institute of Rehabilitation Science, China Medical University, Taichung, Taiwan; Department of Medical Research, Chi Mei Medical Center, Tainan, Taiwan.
Yu-Wen
YW
Chen
Department of Physical Therapy, National Cheng Kung University, Tainan, Taiwan. Electronic address: chhung@mail.ncku.edu.tw.
Ching-Hsia
CH
Hung
Department of Medical Research, Chi Mei Medical Center, Tainan, Taiwan.
Jhi-Joung
JJ
Wang
D000698:Analgesia / Q000379:methods*; D000818:Animals; D003000:Clonidine / Q000008:administration & dosage*; D004305:Dose-Response Relationship, Drug; D004359:Drug Therapy, Combination; D007279:Injections, Subcutaneous; D008297:Male; D008559:Memantine / Q000008:administration & dosage*; D010146:Pain / Q000188:drug therapy* / Q000209:etiology; D010147:Pain Measurement / Q000187:drug effects / Q000379:methods; D010812:Physical Stimulation / Q000009:adverse effects / Q000379:methods; D051381:Rats; D017207:Rats, Sprague-Dawley; D012867:Skin / Q000187:drug effects* / Q000473:pathology
D003000:Clonidine; D008559:Memantine
Clonidine; Infiltrative cutaneous analgesia; Lidocaine; Memantine