Imipramine, Clomipramine and Trimipramine Have Long-acting Spinal Anesthetic Effects

Abstract

Objective: Recently, imipramine, a tri-cyclic antidepressant, was found to be effective in the treatment of neuropathic pain of multiple origins. Also, it was suggested to have a local anesthetic effect, However, its action on spinal function was not fully understood. The aim of this study was to evaluate the spinal anesthetic effect of imipramine. Two commonly used local anesthetics, bupivacaine and lidocaine, were used as controls. Two other tri-cyclic antidepressants, clomipramine and trimipramine, which are analogues of imipramine, were also studied. Materials and Methods: The potencies of the drugs and durations of spinal anesthetic effects on motor function, proprioception, and nociception were evaluated in male Sprague-Dawley rats. Results: We found that all of the drugs tested produced dose-related spinal blockades of motor function, proprioception, and nociception. The spinal blockades of imipramine, clomipramine and trimipramine were more potent than that of lidocaine (p＜0.05 for each comparison). The durations of theft actions were similar to that of the long-acting local anesthetic bupivacaine and longer than that of lidocaine (p＜0.05 for each comparison). Conclusion: Intrathecal imipramine, clomipramine, and trimipramine produce dose-related spinal anesthetic effects which are more potent and longer than that of lidocaine.