Gabapentin enhances anti-nociceptive effects of morphine on heat, cold, and mechanical hyperalgesia in a rat model of neuropathic pain.

Abstract

Neuropathic pain is caused by lesions or diseases affecting the somatosensory system and often responds poorly to typical medications. In this study, we evaluated anti-nociceptive effects of morphine, gabapentin and their combination on heat hyperalgesia, cold and mechanical allodynia in chronic constriction injury (CCI) model of neuropathic pain in rats. Morphine (2, 4 and 8 mg/kg) and gabapentin (5, 10 and 20 mg/kg) were administered either alone or in combination (morphine 2 mg/kg and gabapentin 5 mg/kg). Our results showed that morphine and gabapentin alone produce anti-nociceptive effects at higher doses (morphine 4 and 8 mg/kg and gabapentin 10 and 20 mg/kg) whereas their combination resulted in better analgesia at lower doses as compared to other treatment groups (morphine 2 mg/kg or gabapentin 5 mg/kg). These findings suggest that gabapentin potentiates the analgesic effects of morphine in the chronic constriction injury (CCI) model of neuropathic pain and combination of these drugs may be considered as a beneficial treatment for neuropathic pain.