CDC Issues Urgent Warning Over “Rhino Tranq”: Medetomidine Emerging in Illicit Fentanyl Supply

Public health officials are sounding the alarm on a dangerous new addition to the illegal drug market. The Centers for Disease Control and Prevention (CDC) and the White House Office of National Drug Control Policy (ONDCP) have issued a Health Advisory regarding the increasing detection of medetomidine in the illicit fentanyl supply. Known on the street as “rhino tranq,” “mede,” or “dex,” this potent veterinary sedative is creating a lethal combination that complicates overdose reversals and triggers severe withdrawal syndromes.

What is Medetomidine (“Rhino Tranq”)?

Medetomidine is a sedative and analgesic approved for use in dogs, but it is not approved for human use. It is classified as an alpha-2 agonist, meaning it acts on the nervous system in a manner similar to other veterinary sedatives like xylazine. While a dextro-isomer called dexmedetomidine is approved for procedural sedation in humans, the medetomidine found in the illegal supply consists of racemic mixtures of levomedetomidine and dexmedetomidine.

Evidence suggests these substances are being produced in clandestine laboratories rather than diverted from pharmaceutical sources, as the illegal samples lack the preservatives typically found in medical or veterinary formulations.

The Rapid Rise of a New Threat

The prevalence of medetomidine in the U.S. Drug supply has seen an explosive increase over the last few years. According to surveillance data including wastewater analysis and forensic drug testing:

• 2023: 247 incidences detected in drug samples.
• 2024: 2,616 incidences detected.
• 2025: 8,233 incidences detected.

This represents a more than 3,000% increase in detections. The drug has been identified in at least 18 states and Washington, D.C., with the highest concentrations reported in the Northeast and Midwest regions of the United States.

Why “Rhino Tranq” is Exceptionally Dangerous

The primary danger of medetomidine lies in its synergy with fentanyl. Approximately 98% of medetomidine-positive samples as well contained fentanyl. This combination presents two critical risks:

1. Complicated Overdose Reversal

Because medetomidine is a sedative and not an opioid, it does not respond to naloxone (Narcan). While naloxone can reverse the opioid component of an overdose, it cannot reverse the profound sedation, bradycardia, and hypotension caused by medetomidine. This can make the overdose more lethal and the recovery process more complex for first responders.

2. Severe Withdrawal Syndrome

Regular use of medetomidine can lead to a severe withdrawal syndrome similar to clonidine withdrawal. These symptoms can be life-threatening and may require emergency or intensive care. Withdrawal signs include:

• Tachycardia: Heart rates exceeding 100 beats per minute.
• Severe Hypertension: Dangerously high blood pressure.
• Neurological Distress: Fluctuating alertness and tremors.
• Physical Distress: Intractable nausea, vomiting, and chest pain.

Key Takeaways for Public Health and Safety

Frequently Asked Questions

Does naloxone work on rhino tranq?

Naloxone (OORM) effectively reverses the fentanyl portion of the overdose, but it has no effect on medetomidine. Patients may remain profoundly sedated even after the opioid effects are reversed.

What are the signs of medetomidine intoxication?

Intoxication typically manifests as profound and prolonged sedation, hypotension (low blood pressure), and marked bradycardia, with heart rates sometimes dropping as low as 32 beats per minute.

Where is this drug most commonly found?

While it has been detected across 18 states and D.C., the ONDCP and CDC report the highest concentrations are currently in the Northeast and Midwest regions.