Long-term continuous intrathecal infusion of medications for chronic medical problems is common. We investigated the cause of a cluster of severe neurologic complications in patients with intrathecal catheters.

We performed an epidemiologic cohort study of patients who had intrathecal catheters in place in one neurosurgical practice, to assess the presence of new neurologic complications and associated risk factors.

The practice included 61 patients who received pain medication through implanted intrathecal catheter pumps, 19 of whom were treated with morphine, either alone or in combination with other medications. None of the 42 patients whose drug regimen did not include morphine developed a complication, whereas 8 of 13 patients who received morphine in refills of their pumps during one 4-week period experienced neurologic complications. Three persons underwent laminectomy for sterile abscesses and were left with new paralysis or leg weakness. Testing of two stock bottles from the involved pharmacy, both labeled as containing pure morphine, revealed the presence of methadone in addition to morphine. One of these bottles also contained trace ethanol. A sample of medication aspirated from the pump of a patient prescribed morphine from the same pharmacy was also found to have contained methadone and methanol.

A variety of severe neurologic complications was associated with inadvertent administration of methadone, and perhaps other unintended substances, by means of implanted intrathecal catheters to a group of patients. Medical errors in an outpatient pharmacy led to this outbreak.