[Usefulness of epidural administration of ketamine for relief of postherpetic neuralgia].

Four patients with postherpetic neuralgia had their pain alleviated by epidural administration of ketamine. No oral non-steroidal anti-inflammatory drugs and anti-depressant drugs were effective in all cases. Lidocaine or bupivacaine was administered epidurally to all four patients. When these patients stated that they did not feel pain reduced, they received epidural infusion of ketamine at doses from 5 mg to 20 mg with lidocaine or bupivacaine and their postherpetic neuralgia was controlled. Therefore with these cases, we suspect that epidural administration of ketamine, an antagonist for N-methyl-D-aspartic acid receptor, could be an effective and useful alternative treatment in a patient with refractory postherpetic neuralgia.