dextromethorphan and Herpes-Zoster

We investigated the analgesic effect of dextromethorphan (DM), a non-selective NMDA receptor antagonist, in 25 patients with postherpetic neuralgia (PHN). We administered DM 45mg.day-1 orally for 14 days and then 90mg.day-1 for next 14 days. Decrease in pain intensity and alleviation of allodynia were observed in 9 patients (36%). Side effects with no severe cases occurred in 8 patients (32%) and these were mainly digestive symptoms. We concluded that DM might be useful to treat PHN with allodynia probably due to central sensitization.

Topics: Aged; Analgesics; Dextromethorphan; Female; Herpes Zoster; Humans; Male; Middle Aged; Neuralgia; Receptors, N-Methyl-D-Aspartate

N-methyl-D-aspartate (NMDA) receptors are involved in the development of neuropathic pain. Ketamine, a non-competitive NMDA receptor antagonist, has in several case reports given pain relief but efficacy in dosages tolerated in long-term ketamine treatment is unknown. Another substance with an antagonist action at NMDA receptors and which is approved for peroral administration is dextromethorphan. In a randomized study dextromethorphan was no better than placebo for neuropathic pain but this does not exclude efficacy in selected patients. We report a patient with severe post-herpetic pain resistant to conventional pain treatment which was treated with ketamine for 4 years with good pain relief. The practical application of long-term treatment in different administration forms of ketamine is described. The patient also responded with pain relief in a double-blind trial with oral dextromethorphan.

Topics: Aged; Dextromethorphan; Excitatory Amino Acid Antagonists; Herpes Zoster; Humans; Ketamine; Male; Neuralgia; Pain Measurement; Receptors, N-Methyl-D-Aspartate; Time Factors