Medetomidine in the unregulated opioid supply
To: Ottawa Physicians and Nurse Practitioners
Date: April 9, 2026
From: Dr. Michelle Foote, Associate Medical Officer of Health
Subject: Medetomidine in the unregulated opioid supply
Dear Colleagues,
The Ontario Poison Centre has developed a clinical brief regarding medetomidine as an emerging adulterant in the unregulated opioid supply: Medetomidine in the Unregulated Opioid Supply: A Clinical Brief for Ontario Health Care Providers.
Medetomidine (meh-deh-TOH-mih-deen) is a veterinary sedative that has been detected with increasing frequency in Ontario’s unregulated opioid samples. It was detected in 67% of Ontario fentanyl samples in the latest report from Toronto’s Drug Checking Service. Medetomidine is not approved for human use and can cause prolonged and marked sedation, bradycardia and hypotension. It is often present together with opioids, significantly increasing the risk of overdose and other harms.
Clinical highlights on medetomidine:
- Medetomidine has substantially greater α2-receptor selectivity than xylazine and can produce marked sedation, bradycardia, and hypotension.
- The sedative effects of medetomidine persist after naloxone administration. While naloxone should still be given to reverse the opioid component of toxicity, full arousal may not occur. Some patients may require airway support and monitoring for at least 3–6 hours following acute intoxication.
- Medetomidine withdrawal can be severe, begins within 4–6 hours of last use (or later) and may include anxiety, tremor, diaphoresis, nausea and vomiting, tachycardia, and hypertension, potentially progressing to agitated delirium and autonomic crisis.
- Management of medetomidine withdrawal can be complicated, requiring opioid agonist therapy, alpha-2 agonist therapy, and antiemetics.
- Routine or extended toxicology testing may not reliably detect medetomidine, so recognition is often clinical.
Medetomidine toxicity or withdrawal should be considered in patients with suspected fentanyl exposure whose clinical course (particularly persistent sedation, or disproportionate agitation and autonomic instability) does not follow typical patterns. Consider early consultation with the Ontario Poison Centre (1-800-268-9017) when medetomidine toxicity or withdrawal is suspected.
Additional clinical guidance, including management strategies for a variety of care settings, are available through META:PHI (metaphi.ca/resources):
• Combined Fentanyl/Medetomidine Withdrawal in the ED/Acute Care Setting
• Combined Fentanyl/Medetomidine Withdrawal in the Ambulatory Setting
• Combined Fentanyl/Medetomidine Withdrawal in Withdrawal Management Units
OPH Resources:
Overdose Resources Information for Professionals: Includes local data on overdoses and drug-related deaths and the Find Your Way community resource guide.
StopOverdoseOttawa.ca: Additional information on substance use health and resources, including a toolkit for professionals and service providers. **Subscribe to Stop Overdose Ottawa Alerts to stay up to date on the toxic drug supply.
Mental Health, Addictions and Substance Use Health Services and Resources: Includes print resources and fact sheets that can be shared with patients on medetomidine and other substances.