Continuous brachial plexus blockade in combination with the NMDA receptor antagonist memantine prevents phantom pain in acute traumatic upper limb amputees

Background-Hyperexcitability of N-methyl-D-aspartate acid (NMDA) receptors may play an important role in the development of phantom limb pain (PLP). Aim of the study: To investigate whether early treatment with the NMDA antagonist memantine attenuates phantom pain memory formation in traumatic amputees. Methods: In a randomized, double-blind, controlled trial 19 patients with acute traumatic amputation of the upper extremity were investigated. All patients received postoperative analgesia by continuous brachial plexus anesthesia (ropivacaine 0.375% 5 ml/h) for at least 7 days. In addition, the patients received either memantine (20-30 mg daily, n = 10) or placebo (n = 9) for 4 weeks. Results: Memantine treatment reduced the number of requested ropivacacine bolus injections during the first week and resulted in a significant decrease of PLP prevalence and intensity at 4 weeks and 6 months follow up, but not at 12 months follow up. Conclusions: We conclude that memantine can reduce intensity of phantom limb pain and might also prevent the development of PLP. However, despite the very early begin of treatment; no long-term effect on established PLP was evident. (c) 2006 European Federation of Chapters of the International Association for the Study of Pain. Published by Elsevier Ltd. All rights reserved.