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% 5ml/h) for at least 7 days. In addition, the patients received either memantine (20–30mg 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.