Veterinary drug newly found in illicit opioid supply resistant to naloxone

An article published in the Canadian Medical Association Journal describes five things clinicians and harm reduction workers should know about xylazine, a veterinary medication adulterating the illicit opioid supply.

There is no antidote to the effects of xylazine, and the authors explain that xylazine contamination should be suspected when naloxone appears not to work effectively in people with opioid toxicity.

Xylazine is not approved for use in humans and is increasingly found in illicit drug samples along with fentanyl. People using opioids may be unaware of its presence.

The drug is reported to increase euphoria and can cause sedation, low blood pressure, and slower than normal heart rate. These symptoms can persist after treatment with naloxone. However, treating opioid-induced breathing issues with naloxone and supporting the airway remain the priorities, even when xylazine contamination is suspected.

Xylazine is associated with severe ulcerative wounds distinct from those normally seen with intravenous drug use. Chronic use of xylazine can result in withdrawal symptoms, and other medications may be needed to manage discomfort, irritability, and low blood pressure.

"Xylazine is not part of routine urine drug screens, and there are no approved treatments or reversal agents beyond supportive care," writes Dr. Peter Wu, an internist at University Health Network and the University of Toronto with Dr. Emily Austin of the Hospital for Sick Children (SickKids), Toronto, Ontario.

"Specialized addictions care remains critical to addressing the underlying substance use disorder."