[Analgesic effect of dextromethorphan for postherpetic neuralgia].

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.