Memantine for the treatment of general neuropathic pain: a narrative review.

Neuropathic pain (NP) is difficult to treat and is associated with a decline in quality of life. NP aetiologies are numerous and a number of pathologies display neuropathic characteristics. Of the various N-methyl-d-aspartate antagonists that are alternatives to be recommended in first-line NP treatment, memantine has the safest side-effect profile and has long been approved in Alzheimer's disease. The review covers memantine studies in postherpetic neuralgia, diabetic pain, postoperative pain, complex regional pain syndrome, chronic phantom limb pain, opioid-refractory pain and fibromyalgia. Results were inconclusive because of studies with poor levels of evidence, paucity of trials and small samples. Two recent randomized trials, however, showed significant efficacy of memantine: one demonstrated prophylactic effects against postoperative neuralgia and pain-associated psychological impairment; in the other, memantine improved pain and cognition in fibromyalgia. Both studies found no side effects or adverse events. Given the high rate of therapeutic failure in chronic states, often because of adverse events, the excellent benefit/risk ratio of memantine in these pilot studies encourages further exploration of this drug in NP prevention and in fibromyalgia in larger-scale studies.