Plate Nº 81 · recorded September 29, 2026
Health & Medicine ResearchReported finding
Veterinary Sedative Medetomidine Is Driving a Wave of Severe Withdrawal
Medetomidine, a veterinary sedative up to 200 times stronger than xylazine, is spreading through fentanyl supplies — and severe withdrawal cases needing ICU care have quadrupled.
By Elena Vasquez4 min read854 words
In brief
- Medetomidine, a veterinary sedative 100–200 times more potent than xylazine, is increasingly appearing in street fentanyl supplies.
- At two Philadelphia hospitals, the share of opioid use disorder patients needing dexmedetomidine for severe withdrawal rose from under 6% to about 20% after mid-2024, reaching roughly 32% in the final three months of the study.
- Severe medetomidine withdrawal can cause dangerously elevated heart rate, extreme anxiety, nausea, vomiting, and reports of organ damage if untreated, often requiring ICU-level care.
- The study, published in JAMA Internal Medicine (2026), analyzed data from 2020 through September 2025 and found affected patients were younger and more likely to be on Medicare.
A powerful veterinary sedative called medetomidine is increasingly turning up in street supplies of fentanyl, and the number of patients suffering severe medetomidine withdrawal has quadrupled in recent years, according to a new analysis by researchers at the Perelman School of Medicine at the University of Pennsylvania.
The study, published in JAMA Internal Medicine, confirms what medical professionals treating these patients have observed firsthand: withdrawal from this particular drug is so severe that it often demands specialized care, including infused medications and stays in the intensive care unit (ICU).
"You can't address something you can't see," said the study's co-first author, Tyler Boyce, MD, a fellow in pulmonary and critical care medicine. "Showing how an increase in severe withdrawal cases is a reflection of this drug's emergence in the opioid supply will likely prove valuable to hospitals and public health officials trying to appropriately plan responses."
Hundreds of times more powerful
Medetomidine is used as an anesthetic for larger animals. It is 100 to 200 times more powerful than xylazine, another veterinary drug that has mixed into the illicit opioid supply in recent years. Withdrawal from medetomidine sets in quickly and can cause tachycardia — a severely elevated heartbeat — along with extreme anxiety, nausea, and vomiting, among other symptoms. There have also been reports of organ damage associated with severe, untreated withdrawal.
Treating severe cases is complicated. Patients often need a medication called dexmedetomidine, which is delivered through a continuous infusion and requires an ICU stay because it can cause low heart rates and low blood pressure, both of which demand careful monitoring.
Because this treatment is so resource-intensive, knowing how many people are exposed to medetomidine — and how many suffer its withdrawal — could help hospitals and communities allocate staff, beds, and medications more effectively.
"Patients are coming to us very sick, and we have had to rapidly adapt our treatments to serve the patients in front of us," said senior author Margaret Lowenstein, MD, an assistant professor of general internal medicine and research director for the Penn Center for Addiction Medicine and Policy. "Understanding the impact of this new adulterant and helping clinicians and hospitals prepare to care for affected patients is critical."
Two hospitals reveal the drug's spread
The researchers examined data from two Philadelphia hospitals covering 2020 through September 2025. They used a practical marker: patients with opioid use disorder who received dexmedetomidine were classified as having severe medetomidine withdrawal, since the drug is the standard infused treatment for those symptoms.
Reports of medetomidine appearing in fentanyl supplies trace back anecdotally to mid-2024, so the researchers split their data into periods before and after that point to measure the drug's spread.
In the "pre-medetomidine period," just under 6% of patients with opioid use disorder received dexmedetomidine. In the "post-medetomidine period," roughly 20% of these patients needed it. In the final three months of the study window, that rate climbed to approximately 32%.
"Historically, heroin withdrawal without these adulterants could be managed in outpatient or minimally monitored inpatient settings," said co-first author Ashish Thakrar, MD, an assistant professor of general internal medicine.
"It was striking that, in the last quarter of our study, a third of patients required intensive care unit management for withdrawal from fentanyl mixed with medetomidine," Thakrar added. "Clinically, we recognize that we are in a new era of withdrawal management."
Patients need more intensive treatment
The pattern extended beyond dexmedetomidine alone. Patients suspected of having medetomidine withdrawal were significantly more likely to need additional medications, and higher doses of them, which further suggests their severe symptoms stemmed from medetomidine rather than untreated fentanyl withdrawal.
For example, 79% of the medetomidine withdrawal group received methadone — a long-acting medication that blunts withdrawal effects and opioid cravings — compared with 50% of patients with opioid use disorder who did not require dexmedetomidine. Similarly, 36% of the medetomidine withdrawal group received buprenorphine, another medication in the same family, compared with 26% of patients without medetomidine-related withdrawal.
Patients who received dexmedetomidine also spent more time in the ICU, on average, than other patients with opioid use disorder.
Who is affected
The research team found that patients who required dexmedetomidine were younger and more likely to be on Medicare than other patients with opioid use disorder.
The researchers caution that more analysis is needed. Identifying the risk factors that make some patients more likely to suffer medetomidine withdrawal — and using that knowledge to shape policy or public health interventions — remains an open question.
It is also worth noting the study's limits. The data come from just two hospitals in one city, and the researchers inferred medetomidine exposure indirectly, through dexmedetomidine treatment, rather than through direct drug testing. The findings describe Philadelphia's experience; other regions may differ. Even so, the numbers document a rapid shift in how severe opioid withdrawal is being managed — one that clinicians say has arrived with startling speed.
Publication details: Tyler G. Boyce et al., "Dexmedetomidine Use and Intensive Care Unit Admissions for Patients With Medetomidine Withdrawal," JAMA Internal Medicine (2026). DOI: 10.1001/jamainternmed.2026.4568
via Medical Xpress (Source)