DEXTROMETHORPHAN POTENTIATES THE EFFECT OF MORPHINE IN RATS WITH PERIPHERAL NEUROPATHY

NEUROPATHIC pain responds poorly to opioids. We non/report that combin ation of systemic morphine (2 mg/kg) and dextromethorphan (45 mg/kg), a clinically available antitussive with NMDA-antagonist properties, ma rkedly alleviated mechanical and cold allodynia-like behavior in a rat model of peripheral mononeuropathy. Neither drug produced a significa nt effect on its own at these doses. The anti-allodynic effect of morp hine plus dextromethorphan was reversed by naloxone. The present resul ts suggest that a combination of NMDA-antagonist and opiates might be effective in treating neuropathic pain. Furthermore, the effect of thi s drug combination is mainly mediated via opioid receptors. (C) 1998 R apid Science Ltd.