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.