Medetomidine-Associated Opioid Overdoses in Chicago, Illinois: A Report of 3 Cases

Medetomidine has recently emerged as an adulterant in street-level opioids and stimulants in North America, complicating opioid overdose presentations and resisting reversal with naloxone. Medetomidine is an alpha-2 adrenergic receptor agonist used in veterinary medicine as an anesthetic, analgesic, anxiolytic, and muscle relaxant and is not approved for human use by the Food and Drug Administration. Medetomidine's pharmacological profile resembles xylazine, another medication of the same class, but demonstrates higher potency and longer sedative effects in canine models.

We present 3 cases of opioid overdoses involving medetomidine at the same emergency department, which are part of a larger series of at least 12 confirmed, 26 probable, and 140 suspected cases in Chicago between May 11 and May 17, 2024. Each presented with sinus bradycardia, hypertension, and prolonged sedation, which persisted after naloxone administration. Laboratory results confirmed medetomidine, fentanyl, and other substances in their systems. Management involved symptomatic treatment, including cardiorespiratory support and antihypertensive therapy. Given the severity of their opioid use disorders and social vulnerabilities, patients received extended-release buprenorphine injections. Despite different clinical courses, the cases shared a constellation of features and presenting symptoms likely attributed to medetomidine-associated toxicity.

These cases underscore the clinical challenges of recognizing and managing medetomidine as an emerging drug adulterant. Unlike typical opioid overdoses, medetomidine intoxication may require different management strategies due to prolonged sedation, bradycardia, and hypertension despite standard-of-care overdose treatment. Improved access to testing for medetomidine and research into alpha-2-antagonist reversal options are crucial for optimizing treatment outcomes.