Evaluation of central and peripheral analgesic activity of amitriptyline in mice

Abstract

Background: Pain is one of the most frequent reasons for visiting a doctor. Large-scale studies in Western countries have shown that a fifth of the adult population suffer from chronic pain. Treatment of pain, still a major problem in clinical practice. Despite several available analgesics, unrelieved pain remains a major health care issue. Amitriptyline is a tricyclic antidepressant drug, which is regarded as adjuvant analgesic. There is a common consensus among the researchers on analgesic effect of amitriptyline which is mediated by central pathway but for the peripheral mechanism no conclusive evidence exists till now.Methods: To establish the analgesic mechanism of amitriptyline we tried to evaluate the analgesic activity on different mice models for central (Radiant heat tail flick test and Haffner’s tail clip method) and peripheral analgesia (Writhing test). We also compare the effects of amitriptyline with standard drugs for central and peripheral analgesia.Results: Both in Radiant heat tail flick test and Haffner’s tail clip method we found that the amitriptyline showed significant (p<0.05 to p<0.001) activity as compared to control and diclofenac group. But in comparison to pentazocin group amitriptyline didn’t show significant difference in the reaction time. In acetic acid induced writhing test amitriptyline group mice showed 41.09% reduction in number of writhes as compared to control group. While the standard control (Diclofenac) showed reduction of 65.17% as compared to control. So, amitriptyline showed comparable efficacy towards reduction in number of writhes with that of diclofenac.Conclusions: The results revealed that amitriptyline has significant analgesic activity which is mediated by modulation of both the central and peripheral pathways.