A comparative study of the anti-nociceptive potential of duloxetine and carbamazepine in an animal model of neuropathic pain

Abstract

Background: Pain is one of the most common symptoms encountered in clinical practice. Of the various types of pain, neuropathic pain represents one of the most difficult pain states to treat, with treatments being far from satisfactory. The drugs used are not fully effective and a drug that shows good efficacy in one neuropathic pain state may be ineffective in another. This study was done to compare the antinociceptive potential of duloxetine and carbamazepine, two drugs with different mechanisms of action in an animal model of neuropathic pain.Methods: Antinociceptive effect of duloxetine (15 mg/kg intraperitoneally) and carbamazepine (20 mg/kg intraperitoneally) was evaluated in the sciatic chronic constriction injury (CCI) model of neuropathic pain in rats. Thermal hyperalgesia, evaluated by the hot plate method; and mechanical hyperalgesia, evaluated by the pinprick method were used as measures of neuropathic pain.Results: A significant degree of thermal and mechanical hyperalgesia (p ≤0.05) was produced in both the drug groups. Both drugs produced a significant decrease in thermal and mechanical hyperalgesia throughout the study period (p ≤0.01 for both drugs). In comparison to duloxetine, carbamazepine was less efficacious (p ≤0.05 at 30, 60 minutes; p ≤0.01 at 120 minutes) for thermal hyperalgesia as well as for mechanical hyperalgesia (p ≤0.05 at 30, 60 minutes; p≤0.01 at 120 minutes). Only duloxetine was able to almost completely reverse both thermal & mechanical hyperalgesia to near pre-neuropathy levels.Conclusions: Duloxetine showed better antinociceptive potential as compared to carbamazepine as reflected by a more complete reduction in thermal & mechanical hyperalgesia in the sciatic CCI model of neuropathic pain.