The clinical picture that unfolded was unlike anything clinicians had managed during the fentanyl and xylazine eras. Experts in Philadelphia and Pittsburgh documented a novel, clinically distinct withdrawal syndrome attributable to medetomidine exposure. Patients presented with the familiar hallmarks of opioid withdrawal but layered on top were profound hypertension, with blood pressures frequently exceeding 180/120 millimeters of mercury, and extreme tachycardia, with heart rates climbing above 140 beats per minute. Intractable vomiting, a peculiar tremor without clonus or hyper-reactivity, and even cases of posterior reversible encephalopathy syndrome and myocardial injury appeared in the case series. In one multicenter study of 175 patients, more than 90 percent required intensive care unit admission. Pharmacologically, the explanation lies in medetomidine’s mechanism: as an alpha-2 agonist, it hyperpolarizes norepinephrine-producing neurons in a negative feedback loop, dampening norepinephrine release and producing sedation, analgesia, muscle relaxation, and anxiolysis. When the drug leaves the system, a catastrophic rebound of noradrenergic activity ensues, driving the severe cardiovascular and gastrointestinal chaos clinicians observed.

Recognizing that no coordinated playbook existed for this new threat, the Division of Substance Use Prevention and Harm Reduction at the Philadelphia Department of Public Health partnered with the Health Federation of Philadelphia’s Substance Use Response, Guidance, and Education program to convene a citywide Medetomidine Withdrawal Summit on November 6, 2025. The event, accredited for continuing medical education, pharmacy, nursing, and social work credit, drew 115 attendees. Most were health professionals, including 44 working in medical settings and 45 in behavioral health, spanning physicians, nurses, pharmacists, social workers, substance use navigators, certified recovery specialists, and harm reduction outreach workers from the city’s three academic health systems, correctional health, federally qualified health centers, crisis response centers, residential treatment facilities, and opioid treatment programs. Public health employees, academic researchers, and visitors from Pittsburgh, New Jersey, and New York rounded out the room, a testament to how far word of the emerging syndrome had traveled.

The summit’s architecture was deliberately case-driven, adapted from the structure of Fetal and Infant Mortality Review that the city had previously used to build xylazine wound care guidance. Four vignettes, based on real but de-identified patients, traced medetomidine withdrawal across four care settings. The first illustrated the power of low-barrier, co-located care: a young man with active injection drug use and housing instability living in supportive housing with an attached walk-in clinic, where staff could repeatedly check vital signs, adjust clonidine dosing as his blood pressure climbed to 164/91 mmHg, and escalate to emergency services if he developed vomiting, seizures, a blood pressure above 185/100 mmHg, an abnormal neurologic exam, or a Clinical Opiate Withdrawal Scale score over 20. The second case, an inpatient admission, showed how deceptively mild withdrawal could explode into severe symptoms within four to six hours, forcing escalation to the intensive care unit for a high-dose intravenous dexmedetomidine infusion, followed by an aggressive cross-taper to oral and transdermal alpha-2 agonists and a low-dose buprenorphine induction with transition to long-acting injectable buprenorphine.

The third and fourth vignettes exposed the fault lines in the system. In a residential rehabilitation program operating at ASAM 3.5 and 3.7 levels of care, a walk-in patient’s blood pressure rocketed from 174/98 to 203/108 mmHg within hours of admission, followed by intractable vomiting and an altered mental state that required a 911 call because the facility lacked a 24-hour on-site medical provider and sufficient staffing ratios. In the emergency department case, a young woman who received naloxone from both a bystander and emergency medical services arrived with hypotension and bradycardia, then flipped within two hours to severe hypertension, tachycardia, and intractable vomiting, requiring a demanding combination of intravenous, intramuscular, orally disintegrating, and transdermal medications before stabilizing on methadone maintenance. Together, the cases underscored the razor-thin therapeutic window for preemptive oral management and the critical importance of vigilant vital sign monitoring to track withdrawal progression.

A panel of emergency physicians, addiction medicine and toxicology consultants, primary care and opioid treatment physicians, and a clinical pharmacist distilled hard-won lessons for the audience. The Clinical Opiate Withdrawal Scale, long the standard instrument, appeared to underestimate severity in patients afflicted by a hypoactive delirium that many now recognize as a distinctive feature of severe medetomidine withdrawal. With no validated instrument for alpha-2 withdrawal, panelists urged clinicians to rely on elevated heart rate and blood pressure as more reliable indicators and to titrate treatments such as dexmedetomidine infusions to vital signs rather than mental status. Clonidine emerged as the mainstay of management, available in oral tablets and transdermal patches at three doses each, though the panel noted that patches may not be covered by outpatient insurance despite being on Pennsylvania’s medical assistance preferred drug list. Two pharmacokinetic insights proved especially valuable: transdermal clonidine takes 24 to 48 hours to deliver relief, and oral clonidine tablets can be absorbed sublingually with no loss of efficacy when patients cannot swallow, a practical workaround for a syndrome defined by vomiting.

Concurrent opioid replacement with intravenous or oral hydromorphone and methadone was identified as essential, with gabapentin serving as a helpful though dependency-risking adjunct for mild to moderate symptoms. Panelists also flagged that patients who become ‘quiet’ are often the most endangered, since decreased responsiveness signals the need for urgent transfer to a higher level of care. Managing withdrawal in pregnant patients proved especially thorny, as typical antiemetics proved ineffective and pregnancy antihypertensives failed to address the underlying withdrawal mechanism; the consensus held that clonidine’s benefits outweighed the risks of undertreated withdrawal, with lorazepam as the preferred benzodiazepine should one be needed during pregnancy. Dopamine antagonist agents such as metoclopramide, olanzapine, prochlorperazine, haloperidol, and chlorpromazine were reported anecdotally to control the syndrome’s relentless nausea and vomiting, thereby enabling patients to tolerate the oral clonidine that forms the backbone of treatment.

The breakout sessions generated 74 insights grouped into nine themes: overdose response, clinical recognition of withdrawal, monitoring, treatment approach, patient care navigation, workforce development, testing and surveillance, mobile outreach, and reimbursement. From these, the authors formulated twelve recommendations. Among them: fund community-based drug checking programs that deliver rapid, accurate results; include harm reduction networks in medetomidine information dissemination; keep naloxone as the first-line response to opioid overdose, redosing only when breathing is inadequate; monitor closely for rapid shifts between intoxication and withdrawal phases, using heart rate trends to distinguish bradycardic intoxication from tachycardic withdrawal; refer patients with profound hypertension for acute medical evaluation given the risk of neurologic and cardiac injury; treat a prior need for a dexmedetomidine infusion as the best predictor of future severe withdrawal, a better marker than current volume of drug use; align reimbursement with the true complexity of care; establish an ICD code for medetomidine withdrawal to enable surveillance and billing; and fund free accredited education for all medical and behavioral health team members.

Philadelphia’s broader response infrastructure offers a model worth emulating. The city’s health department has worked with the Center for Forensic Science Research and Education’s NPS Discovery early warning system since September 2020, collaborating with PA Groundhogs, an organization that conducts drug checking directly with people who use drugs. New rapid medetomidine testing strips now allow surveillance at the individual level. A cascade of Health Alerts began in May 2024, followed by more detailed alerts in December 2024, a CHART data publication in May 2025, and a June 2025 Health Update with granular guidance for non-hospital settings. The authors acknowledge the descriptive limitations of their summit report and call for quantitative evaluations of clinician confidence, compensation for people with lived experience in provider training, and stronger discharge planning and outpatient tapering protocols. But their central conclusion rings clear and increasingly urgent: proactive coordination among hospitals, community organizations, and public health agencies, grounded in case-based education and honest information exchange, is the essential foundation for confronting not just medetomidine, but the relentless, unpredictable evolution of the drug supply itself.

Subject of Research: The public health response to medetomidine, a new psychoactive adulterant in the illicit opioid supply causing a severe withdrawal syndrome in Philadelphia.

Article Title: Responding to medetomidine in Philadelphia: narrative summary of the public health response to a new psychoactive substance

Article References: Warrick-Stone, T., Simpson, S.-E., Durney, P., Goodstein, D., Abrams, C., Bobb, R., London, K., & Teixeira da Silva, D. (2026). Responding to medetomidine in Philadelphia: narrative summary of the public health response to a new psychoactive substance. Addiction Science & Clinical Practice, 21(1), Article 64. https://doi.org/10.1186/s13722-026-00713-y

Image Credits: AI Generated

DOI: 10.1186/s13722-026-00713-y

Keywords: medetomidine, opioid crisis, withdrawal syndrome, Philadelphia, public health, fentanyl adulterants, harm reduction, drug checking, clonidine, alpha-2 agonist, substance use treatment, health surveillance