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Abstract

To investigate and compare the analgesic effect of fluoxetine (FLU), duloxetine (DUL) and venlafaxine (VEN) in animal models of chronic pain. Methods: Chronic pain was induced in albino rats using spared nerve injury and vincristine. Rats were divided into Control group/ Normal Saline (NS5), DUL group, FLU group, and VEN group. In spared nerve injury, sural branch of sciatic nerve was kept intact while another two branches, common peroneal and tibial nerve ligated and cut. In the vincristine-induced neuropathic pain model, vincristine was administered along with test drugs for 5 days and then 2 days gap and then for 5 days. Mechanical allodynia and hyperalgesia developed in animals were indicative of pain. Pain assessment was done by using von frey filaments by measuring paw withdrawal threshold (PWT) on day 7 in spared nerve injury and on 7 and 14 days of vincristine administration. Results: In spared nerve injury, DUL and FLU showed a significant increase in PWT compared to the control group. Venlafaxine had no analgesic action in spared nerve injury model of neuropathic pain. DUL and FLU showed significant reversal of mechanical allodynia. There was no difference between the analgesic activity of fluoxetine and venlafaxine. DUL significantly reverses the development of mechanical allodynia as compared to fluoxetine and venlafaxine. Conclusion: Duloxetine was more effective as an analgesic than fluoxetine and venlafaxine in neuropathic pain.