WASHINGTON (TNND) — Federal health officials warned that a powerful veterinary sedative is increasingly being found in the U.S., raising the risk of overdose and severe withdrawal symptoms.

In a Health Alert Network notice, the Centers for Disease Control and Prevention (CDC) on Thursday said the drug medetomidine -- also known as "rhino tranq" -- is being detected alongside fentanyl and other illicit opioids, complicating treatment for overdoses and addiction.

The agency said the alert was issued in coordination with the White House Office of National Drug Control Policy (ONDCP), which has been tracking the rapid spread of the substance across the country as part of broader efforts to monitor emerging drug threats.

FILE - Bullet holes are seen in windows at the Centers For Disease Control (CDC) Global Headquarters following a shooting that left two dead, on Aug. 9, 2025 in Atlanta. (Photo by Elijah Nouvelage/Getty Images)

The CDC said medetomidine was first identified in the U.S. illegal drug supply in 2021 "and began appearing sporadically with fentanyl in multiple jurisdictions," including Chicago, Philadelphia, and Pittsburgh, from mid-2023 to mid-2024.

By late July 2024, the drug was detected in samples and biological specimens from people who use illegal opioids in at least 18 states and the District of Columbia, the agency said.

Medetomidine, which is not approved for human use, is commonly used as an anesthetic in animals and has effects similar to xylazine, another veterinary tranquilizer that has already contributed to rising overdose risks.

Officials said the drug can cause deep sedation, slowed breathing and dangerous cardiovascular effects, particularly when combined with opioids. It has also been linked to a severe withdrawal syndrome that may require intensive medical care and can be difficult to treat with standard therapies.

The CDC and ONDCP said the emergence of medetomidine highlights the increasingly complex and evolving nature of the illicit drug supply, which now frequently includes multiple substances that can make overdoses harder to detect and treat.

Public health agencies are urging clinicians, first responders and laboratories to increase testing and surveillance, as well as improve coordination across health systems to better identify and respond to new substances entering the drug market.