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

Objective(s):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. Materials and Methods: Morphine (۲, ۴ and ۸ mg/kg) and gabapentin (۵, ۱۰ and ۲۰ mg/kg) were administered either alone or in combination (morphine ۲ mg/kg and gabapentin ۵ mg/kg). Results:Our results showed that morphine and gabapentin alone produce anti-nociceptive effects at higher doses (morphine ۴ and ۸ mg/kg and gabapentin ۱۰ and ۲۰ mg/kg) whereas their combination resulted in better analgesia at lower doses as compared to other treatment groups (morphine ۲ mg/kg or gabapentin ۵ mg/kg). Conclusion: 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.

Keywords:

Gabapentin , Hyperalgesia , Neuropathic pain , Morphine