Persistent pain associated with long-term intrathecal morphine administration

A 32-year-old man with chronic intractable right lower extremity pain unresponsive to multiple neurosurgical and pharmacologic treatments, including intrathecal morphine administration, was successfully treated with sciatic nerve block, discontinuance of opioid therapy, and psychologic interventions. Plasma and urine ratios of morphine metabolites morphine-3- glucuronide and morphine-6-glucuronide were analyzed at the beginning of our interventions, and the results indicated that morphine-3-glucuronide levels were significantly higher than morphine-6-glucuronide levels. The possible association between the observed morphine metabolite ratio and the intractable pain in patients resistant to opioids may have potential clinical implications.