Philadelphia clinicians first flagged medetomidine in the spring of 2024. A cluster of overdoses over a single weekend stood out because patients were more sedated and had slower heart rates than expected even after receiving naloxone. Alarming, yes, but the local drug supply changes so often that the signal didn't set off major alarms. None of those patients died, and most went home the same day.
The picture changed in the autumn. Patients began arriving with severe withdrawal, and that's when doctors understood the supply had shifted in a way that mattered.
Withdrawal was the real problem
Jeanmarie Perrone, an emergency medicine physician who directs the Penn Medicine Center for Addiction Medicine and Policy, said it took time for patients to be exposed to enough medetomidine that stopping would trigger rapid withdrawal. "It's the withdrawal that has caused so many problems," she said.
The American Society of Addiction Medicine has now published its first national guidance on recognizing and treating patients who've taken the sedative. ASAM calls the document "considerations" rather than guidelines, and that distinction is deliberate. Larger studies that could validate what clinicians are seeing on the ground haven't been done yet, so the authors are describing experience, not settled evidence.
Naloxone first, then basic care
Medetomidine almost always shows up mixed with illicit opioids, so naloxone remains the first move when someone appears to be overdosing. The complication is that a patient may stay unresponsive even after breathing resumes. For the low heart rate and low blood pressure that medetomidine causes, the guidance points to IV fluids and other basic supportive care.
Withdrawal follows a different script. The earliest signs are nausea and vomiting, and unlike opioid withdrawal, diarrhea usually isn't part of the picture. Clonidine is the recommended first treatment. Like medetomidine and xylazine before it, clonidine is an alpha-2 agonist, which is why it's pharmacologically logical here. If it doesn't help, or patients can't keep it down, blood pressure can spike and heart rate can climb within a few hours. At that point, clinicians may need dexmedetomidine (Precedex) given intravenously.
Why this one is harder
Kory London, an emergency physician and addiction specialist at Thomas Jefferson University, didn't contribute to the considerations but treats many people who did. His reaction was blunt. "It's scary," he said. "We thought we were already living in unprecedented times with the adulteration of fentanyl with xylazine."
Withdrawal from most illicit drugs doesn't usually land people in intensive care. Medetomidine withdrawal can. London said the doses of clonidine and dexmedetomidine needed to keep patients out of the ICU are higher than he would have considered when xylazine first appeared in the supply. "Unless you're experienced with this, giving enough medications to avoid getting somebody to the ICU is really challenging," he said.
The comparison to xylazine is instructive. Xylazine was the dominant adulterant across much of the American drug supply, and it left users with severe wounds. It also sedated people for hours, often leaving them vulnerable in public. Medetomidine doesn't appear to produce the same wounds. What it does produce is a much more potent sedative effect, and that's what makes it dangerous in a different way.
A moving target
Medetomidine had turned up in at least 18 states by the end of 2025. Its symptoms can overlap with sepsis, which makes knowing whether medetomidine is in the local supply a practical concern for physicians, not an academic one.
Michael Lynch, a medical toxicologist at the University of Pittsburgh Medical Center and a co-author of the considerations, put the problem simply. "The next thing, and then the next thing, and then the thing after that are coming," he said. "We can try to predict what they're going to be, but we can't always."
Not every community can afford regular drug checking, and Lynch's answer is to share what the early adopters learn. "If we do a good job at describing our experience in places where we do have resources and have that early experience, hopefully other places can see the clinical manifestation," he said. Test strips for medetomidine do exist, which helps where checking is possible.
The craving problem
The guidance gives clinicians a working blueprint, but the experts I'd want to hear from are clear that the long-term effects of the drug are still unknown, and treatments built specifically for it are thin.
One concern stands out. Some patients get through withdrawal and start medications for opioid use disorder, yet they still feel cravings. They may assume those cravings are for opioids and relapse, when the pull is actually toward medetomidine. London framed the stakes plainly: "We're going to have to recognize that there are now patients who are developing a sort of novel substance use disorder of alpha-2 agonist sedative addiction. We urgently need both ways to understand that and ways potentially to help treat patients."
Whether clinics can tell those two cravings apart in time may determine how many of these patients end up back in the ICU.