Opioidergic mechanisms are not involved in the antihyperalgesic effects of carbamazepine and oxcarbazepine.

The mechanisms of the analgesic action of carbamazepine and oxcarbazepine, in particular the role of opioid receptors, have not been established precisely. The systemic effects of naloxone, an opioid receptor antagonist, on the antihyperalgesic effects of carbamazepine and oxcarbazepine were examined in the model of inflammatory hyperalgesia induced by the intraplantar (i.pl.) administration of concanavaline A (Con A, 0.8 mg/paw) into the rat hind paw. Naloxone (3 mg/kg; i.p.) did not alter the antihyperalgesic effects of either carbamazepine or oxcarbazepine. These results indicate that the opioid system of pain modulation does not play a significant role in the antihyperalgesic effects of carbamazepine and oxcarbazepine.