BACKGROUND: Neuropathic pain is resistant to conventional treatments, and may seriously affect the quality of life. Insufficient has been done on drug combination for the treatment of neuropathic pain. So we undertook to determine the effect of ketamine and steroid on mechanical hyperalgesia in rats with spinal nerve ligation.

METHODS: Rats were administerend L5 and L6 spinal nerve ligation to cause mechanical hyperalgesia. Control group (n = 6) were administered normal saline 5 ml intraperitoneally, the ketamine group (n = 6) ketamine 1mg/kg, and the steroid group (n = 6) ketamine 1 mg/kg and methylprednisolone 10 mg/kg. Mechanical hyperalgesia was assessed using a von Frey filament before injection, and then 15, 30, 60, 120, and 180 min after injection.

RESULTS: Ketamine 1 mg/kg significantly attenuated mechanical hyperalgesia for 60 min. The combination of ketamine 1 mg/kg and methylprednisolone 10 mg/kg also significantly attenuated mechanical hyperalgesia. But the combination group did not exert a superior attenuating effect than ketamine alone.

CONCLUSIONS: The combination of ketamine and metylprednisolone did not exert a superior antinociceptive effect than ketamine alone in rats with spinal nerve ligation.