The Centers for Disease Control and Prevention (CDC) issued a health advisory on Thursday, highlighting increasing reports from U.S. jurisdictions of the veterinary sedative medetomidine appearing in the illegal drug supply.
The CDC and the White House Office of National Drug Control Policy alerted public health officials, clinicians, laboratory personnel, and individuals at risk of overdose, noting that medetomidine has been found mixed with fentanyl and associated with severe withdrawal symptoms following exposure.
Medetomidine, commonly referred to as “rhino tranq” or “dex,” is a veterinary sedative approved for use in dogs for sedation and pain relief, but it is not approved for human use.
According to the CDC, the drug has been increasingly detected in law enforcement seizures, samples of illicit drugs and paraphernalia, and even in wastewater testing, with the highest concentrations reported in the Northeast U.S.
Health officials warn that stopping medetomidine after repeated exposure can lead to severe withdrawal symptoms, including high blood pressure, anxiety, nausea, vomiting, and fluctuating levels of alertness, which may require emergency or intensive care. In addition, medetomidine can cause profound sedation, dangerously slow heart rate, and low blood pressure in those exposed.
Since fentanyl is present in most overdoses involving medetomidine, opioid overdose reversal drugs like naloxone should be used to help restore normal breathing.
Medetomidine was first detected in the illicit drug supply in 2021 and began appearing sporadically alongside fentanyl in several U.S. cities including Chicago, Philadelphia, and Pittsburgh between mid-2023 and mid-2024.
From October 2025–January 2026, medetomidine was detected in treated wastewater every week in at least one of 14 states included in a wastewater testing program in the U.S., the CDC said.
