Evaluation of the Neurological Safety of Epidural Milnacipran in Rats

BACKGROUND: Milnacipran is a balanced serotonin norepinephrine reuptake inhibitor with minimal side effects and broad safety margin. It acts primarily on the descending inhibitory pain pathway in brain and spinal cord. In many animal studies, intrathecal administration of milnacipran is effective in neuropathic pain management. However, there is no study for the neurological safety of milnacipran when it is administered neuraxially. This study examined the neurotoxicity of epidural milnacipran by observing behavioral and sensory-motor changes with histopathological examinations of spinal cords in rats. METHODS: Sixty rats were divided into 3 groups, with each group receiving epidural administration of either 0.3 ml (3 mg) of milnacipran (group M, n = 20), 0.3 ml of 40% alcohol (group A, n = 20), or 0.3 ml of normal saline (group S, n = 20). RESULTS: There were no abnormal changes in the behavioral, sensory-motor, or histopathological findings in all rats of groups M and S over a 3-week observation period, whereas all rats in group A had abnormal changes. CONCLUSIONS: Based on these findings, the direct epidural administration of milnacipran in rats did not present any evidence of neurotoxicity in behavioral, sensory-motor and histopathological evaluations.