Efficacy of intravenous magnesium in neuropathic pain

Background. Postherpetic neuralgia is a complication of acuteherpes zoster characterized by severe pain and paraesthesiain the skin area affected by the initial infection. There isevidence that the N-methyl-D-aspartate receptor is involvedin the development of hypersensitivity states and it is knownthat magnesium blocks the N-methyl-D-aspartate receptor. Method. A double-blind, placebo-controlled, cross-over studywas conducted in which magnesium sulphate was administered asan i.v. infusion. Spontaneous pain was recorded and qualitativesensory testing with cotton wool was performed in seven patientswith postherpetic neuralgia before and after the i.v. administrationof either magnesium sulphate 30 mg kg^–1 or saline. Results. During the administration, pain scores were significantlylower for magnesium compared with placebo at 20 and 30 min (P=0.016)but not at 10 min. I.V. magnesium sulphate was safe, well-toleratedand effective in patients with postherpetic neuralgia. Conclusion. The present study supports the concept that theN-methyl-D-aspartate receptor is involved in the control ofpostherpetic neuralgia. Br J Anaesth 2002; 89: 711–14