Stanciu 2020: naltrexone, noroxymorphone and a misleading urine test

What they tested

People in substance use treatment are often monitored with urine drug screens, and a positive result can have serious consequences, sometimes including being dropped from the program. The authors describe one case to show how naltrexone's breakdown products can complicate those results.

The body breaks naltrexone down in several steps. One minor product, noroxymorphone, gets very little mention in the medical literature, but it is also the last step in the breakdown of oxycodone, so clinicians naturally assume it means oxycodone use.

What they found

Confirmatory testing found noroxymorphone on its own, without any of the other products expected from oxycodone, in a person taking naltrexone.

The authors conclude that, depending on individual pharmacogenomics (how a person's genes affect the way drugs are broken down), naltrexone can produce a positive confirmation for noroxymorphone.

Limits

• It describes one person, so it can't show how often this happens.
• The abstract doesn't give details of the patient, the dose or the testing methods.

What it means if you're considering naltrexone

For someone on naltrexone whose urine test shows noroxymorphone but none of oxycodone's other breakdown products, this report gives clinicians a reason to consider naltrexone itself before assuming oxycodone use. A later case report, from 2024, described a similar pattern.