The CDC and the White House Office of National Drug Control Policy are warning clinicians that medetomidine, used to sedate dogs, is increasingly being detected in the illicit drug supply and that it has been associated with a severe withdrawal syndrome.

Known as “rhino tranq,” “mede,” or “dex,” medetomidine is not approved for human use, but its dextro isomer, dexmedetomidine, is approved for procedural sedation in humans, according to the health alert.

The sedative is most often found mixed with fentanyl. The agency reported that it believes the medetomidine is being purposefully introduced into the illicit supply because preservatives commonly found in medical or veterinary formulations have not been detected.

The “findings suggest medetomidine is being synthesized in clandestine laboratories,” CDC officials said.

The alert was issued online on April 2.

Nationwide Spread

Medetomidine was first detected in the US in 2021, appearing sporadically with fentanyl in the illicit drug supply in Chicago, Philadelphia, and Pittsburgh.

The University of North Carolina’s Street Drug Analysis Lab has also reported medetomidine in samples submitted to the lab, first detecting the substance in late 2022.

Medetomidine has been increasingly detected in law enforcement drug seizures, with reports to the National Forensic Laboratory Information System increasing by 950% between 2023 and 2024 and another 250% in 2025. The number of reports rose from 247 in 2024 to 8233 in 2025.

Detection of the drug in wastewater samples has also increased. Between October 2025 and January 2026, medetomidine was found in wastewater every week in at least 1 of 14 states that participate in a wastewater testing program, said the CDC.

Although the highest concentrations have been found in the Northeast, medetomidine has been detected in all areas of the country, with up to half of opioid-positive samples at some sites in the Midwest containing the sedative.

Advice for Clinicians

The CDC advises that clinicians consider medetomidine as a potential intoxicant when a patient experiences prolonged sedation after naloxone administration.

Anti-overdose medications do not reverse medetomidine overdose, but because opioids such as fentanyl are almost always co-involved, naloxone should continue to be administered as long as necessary, said the agency.

Medetomidine withdrawal symptoms are similar to those experienced during clonidine withdrawal and include tachycardia (> 100 beats/min), severe hypertension, fluctuating alertness, tremor, chest pain, and intractable nausea and vomiting. Symptoms may begin within hours of last use and peak 18-36 hours later, according to the CDC.

The CDC alert reports three potential events in which a large number of patients likely experienced severe medetomidine withdrawal: in Philadelphia from September 2024 to January 2025, in Pittsburgh from October 2024 to March 2025, and in Maryland during summer 2025.

Withdrawal should be considered when patients exhibit any of the associated symptoms or do not improve after standard opioid withdrawal treatment.

The alert said that “emerging guidance” suggests that withdrawal can be managed through opioid withdrawal protocols; alpha-2 agonist therapy with clonidine and dexmedetomidine, if needed; treatment of agitation as needed; and hypertension management (preferably via withdrawal management).

Complete clinician guidance can be found in the CDC health alert.

Alicia Ault is a Saint Petersburg, Florida-based freelance journalist whose work has appeared in many health and science publications, including Smithsonian.com. You can find her on X @aliciaault and on Bluesky @aliciaault.bsky.social.