Fatal drug combination sparks alert as 'rhino tranq' spreads across US

The Centers for Disease Control and Prevention (CDC) and the White House Office of National Drug Control Policy (ONDCP) issued a health advisory on Thursday about reports of medetomidine being detected in fentanyl.

The advisory is based on surveillance data, including forensic drug testing, wastewater analysis, clinical case reports and overdose investigations.

In 2023, there were 247 incidences of medetomidine detected in drug samples, which rose to 2,616 in 2024 and 8,233 in 2025 - a more than 3,000% increase. Forensic drug reports showed that about 98% of medetomidine-positive samples also contained fentanyl. 

The drug has been detected in at least 18 states and Washington, D.C., with a concentration in the Northeast and Midwest regions of the U.S., per the CDC alert.

"Its co‑occurrence with fentanyl significantly complicates overdose presentation and withdrawal management, further increasing both clinical acuity and unpredictability," he told Fox News Digital.

Naloxone (Narcan), known for its overdose reversal effects, does not counteract medetomidine, the advisory warned.

Withdrawal symptoms typically begin about a few hours after taking medetomidine. They can be severe and rapid, peaking at about 18-36 hours, according to experts.

Severe cases require intensive care in a hospital. "Management may require ICU‑level monitoring and care," said Scioli.

In a May 2024 example cited by the CDC, medetomidine in the illegal opioid supply was linked to a cluster of overdoses in Chicago, potentially exceeding 175. At least 16 people were hospitalized and one died.

There were some limitations to the surveillance, the agency acknowledged. Surveillance systems rely on small samples that may not be representative of all areas.

There is also the chance that the numbers could be overestimated due to contamination or repeated use of drug paraphernalia. Conversely, numbers could actually be higher than recorded, as medetomidine is rapidly metabolized in the body and is not typically tested in clinical settings.

The surveillance was conducted by the CDC with support from federal public health programs and collaboration with other agencies.

"The drug supply is evolving in ways that strain traditional opioid‑focused frameworks and demand greater clinical vigilance," he said.