Medetomidine fentanyl mixtures are now turning up on US streets, and doctors say naloxone cannot fix the problem. Medetomidine is a drug meant to sedate animals before surgery. It was never approved for use in people, and it does not respond to naloxone the way opioids do.

Doctors are watching patients go into a withdrawal syndrome so severe it can require life support. Blood pressure spikes, the heart races, and standard withdrawal medication often fails to bring it under control. There is still no approved antidote for medetomidine in humans, only two reversal drugs, and both are cleared for veterinary use only.

Xylazine did the same thing a few years back, a different veterinary sedative that spread through the fentanyl supply faster than doctors could adapt their treatment protocols. Medetomidine looks to be heading the same way, and an addiction medicine doctor at Yale has just put the warning in writing.

Source: DB Recovery Resources, New additive in US opioid supply