Epidural morphine for postherpetic neuralgia.

Eleven patients with established postherpetic neuralgia, unresponsive to antidepressant therapy, entered this single-blind, placebo-controlled study to assess the effectiveness of epidural morphine in the control of the pain of postherpetic neuralgia. Two patients obtained a reduction in pain of greater than 50% following morphine 0.5 mg. The duration of this pain relief was 36 h in one patient and 72 h in the other. Repeated doses, however, were ineffective in one patient and resulted in intolerable side effects in the other. The other six patients who received morphine developed opioid-related side effects without pain relief. Three patients did not receive morphine as they gained significant, long-lasting pain relief from placebo. Two retained that benefit for more than 6 months. Epidural morphine is more likely to produce side effects than pain relief when administered to patients with postherpetic neuralgia.