People hospitalized after using fentanyl contaminated with the veterinary sedative medetomidine described sedation they could not fight off and withdrawal that standard treatment did not fully relieve, according to a brief research report published this week in Annals of Internal Medicine. Researchers at the University of Pittsburgh School of Medicine interviewed 16 adults with opioid use disorder who had confirmed medetomidine exposure and were hospitalized between September and November 2025.
Participants said they felt powerless to avoid the drug and that the extreme sedation made them more vulnerable to harm. Many said standard medications for opioid use disorder did not adequately address their symptoms, according to a summary from the American College of Physicians, which publishes the journal.
The findings matter beyond one hospital system because medetomidine has spread through the illicit fentanyl supply, particularly in the Northeast and Midwest. For families and caregivers, the practical concern is recognizing when withdrawal has become a medical emergency.
Patients Describe Sedation and Withdrawal Beyond Their Control
"It will knock you out no matter what, you couldn't even fight it," a 31-year-old woman in the study said, as quoted by STAT. Participants told researchers that passing out after use is common, and that passing out in public increases the risk of being robbed or assaulted.
The authors concluded that health systems and clinicians need greater awareness of medetomidine, better surveillance of the drug supply, and clinical protocols for its distinct withdrawal and treatment challenges.
This is a small interview-based study. It captured the experiences of 16 hospitalized patients, so it cannot show how common severe withdrawal is, cannot prove that medetomidine alone caused each patient's symptoms, and may not reflect people who never reached a hospital. MedicalDaily was unable to review the full text, including funding and conflict-of-interest disclosures, before publication.
Larger clinical data point in the same direction. A case series of 209 patients across three Philadelphia hospital systems, published in the Journal of Addiction Medicine, included people hospitalized between September 2024 and April 2025 with opioid withdrawal complicated by severe overactivation of the body's fight-or-flight system. Of those patients, 77.5% were admitted to intensive care, 20.1% needed a breathing tube, and 73.7% received dexmedetomidine infusions. Symptoms often did not respond to standard opioid withdrawal treatment. The authors described the withdrawal as occurring around the same time as medetomidine exposure, which is an association, not proof of cause.
A Sedative Now Common in the Fentanyl Supply
Medetomidine, also sold on the street as rhino tranq, mede, or dex, is not approved for human use. Detections in illicit drug seizures rose from 247 in 2023 to 8,233 in 2025, mainly in the Northeast and Midwest, according to a health advisory from the White House and CDC.
In New York City, the Health Department reported that medetomidine appeared in 32% of samples sold as opioids and tested through its drug checking program in 2025, and nearly all of those samples also contained fentanyl. The department said prevalence had remained relatively stable since April 2025.
The department also said drug withdrawal-related emergency department visits were higher in every quarter of 2025 than in earlier quarters, although those visits had been rising since 2021, well before medetomidine was first identified in the city's opioid supply in May 2024.
"It is the constant change of molecules that resets the harm for every generation, every few years," Nabarun Dasgupta, an epidemiologist and harm reduction advocate, told STAT.
"Medetomidine represents a real threat to communities," Sara Carter, director of National Drug Control Policy, said when the federal advisory was released.
Warning Signs Families Should Not Ignore
Medetomidine intoxication can cause a very slow heart rate, reported as low as 32 beats per minute, along with low blood pressure and deep, often prolonged sedation, according to federal and New York City health officials. A person may still be breathing but not respond to voice or touch.
Withdrawal looks very different. The New York City Health Department lists a heart rate above 100 beats per minute, blood pressure above 180/100, heavy sweating, shaking or twitching, anxiety or agitation, nausea with uncontrollable vomiting, chest pain, and alertness that comes and goes. The department says the syndrome may require hospital care. Families should treat chest pain, very high blood pressure, confusion, or nonstop vomiting as reasons to seek emergency care.
For a suspected overdose, call 911 and give naloxone. Naloxone reverses opioids such as fentanyl but not medetomidine's sedation, so a person may stay sedated after receiving it and still needs medical monitoring. The CDC health advisory includes recommendations for clinicians and people at risk of overdose.
Caregivers can help by telling emergency staff about possible medetomidine exposure. The New York City Health Department says emerging guidance pairs opioid withdrawal treatment with alpha-2 agonist medications, such as clonidine and dexmedetomidine, when needed. It also notes that there is no evidence-based consensus on best practices yet and that recommendations will likely change. Severe withdrawal should not be managed at home, and no one should stop or adjust prescribed addiction medication without a clinician.
People who use drugs alone can call the Never Use Alone hotline at 877-696-1996, which is listed in the New York City advisory. Anyone in crisis can call or text 988, and the national Poison Help line is 1-800-222-1222. Local health departments and syringe service programs can also connect people to treatment.
MedicalDaily previously reported on the federal advisory warning that naloxone alone cannot reverse medetomidine. The new report adds patients' own accounts of withdrawal and gaps in treatment. Larger studies are still needed to define standard protocols. The practical takeaway remains the same: know the warning signs, carry naloxone, and seek hospital care for severe withdrawal.
Key Questions Answered
What is medetomidine? It is a veterinary sedative, not approved for human use, that has been found mixed into illicit fentanyl. The New York City Health Department describes it as similar to xylazine but more potent and longer-lasting.
What did the new study find? Sixteen hospitalized patients described extreme sedation, feeling powerless to avoid exposure, and severe withdrawal that standard opioid use disorder medications often did not adequately address.
Is medetomidine withdrawal dangerous? It can be. In a Philadelphia case series of 209 patients hospitalized with severe withdrawal, 77.5% were admitted to intensive care. Warning signs include a racing heart, very high blood pressure, vomiting, and chest pain.
Does naloxone work? Naloxone reverses opioids such as fentanyl but not medetomidine's sedation. Health officials still advise giving naloxone and calling 911 for any suspected overdose.
Is medetomidine becoming more common in New York City? New York City health officials found it in 32% of tested samples sold as opioids in 2025 and said its prevalence had been relatively stable since April 2025.
