Clinical Presentation of Medetomidine-Involved Opioid Overdoses-Chicago, 2024

Medetomidine, an alpha-2 adrenergic agonist, emerged as a U.S. drug adulterant in 2022. In May 2024, the Chicago Department of Public Health identified a cluster of opioid overdoses with unusual clinical features linked to medetomidine.

We performed a retrospective chart review of patients presenting to three Chicago emergency departments with suspected opioid-involved overdoses during May 11-17, 2024. We classified cases as confirmed, probable, or suspected based on independent clinical criteria and laboratory screening results. We performed descriptive statistics and exploratory logistic regression to assess the association between case status and hospital outcomes.

Out of 181 patients presenting with suspected opioid-involved overdoses during the one-week window, 15 patients identified during the initial phase of the outbreak underwent supplemental testing, yielding 12 laboratory-confirmed cases of medetomidine exposure. In patients with confirmed medetomidine exposure (n = 12), all exhibited persistent altered mental status despite naloxone administration and demonstrated marked hypertension at presentation. Bradycardia was present in 9 patients (75%). Compared to suspected cases, confirmed or probable cases had a higher odds of experiencing asymptomatic markedly elevated blood pressure (OR = 3.2, 95% Cl = 1.5-6.9), hospital admission (OR = 3.2, 95% Cl = 1.4-7.3), and admission to intensive care (OR = 4.0, 95% Cl = 1.4-11.8).

Patients with confirmed medetomidine exposure demonstrated a toxidrome characterized by initial asymptomatic markedly elevated blood pressure, bradycardia, and a prolonged altered mental status requiring clinical stabilization. The increased likelihood of hospital and intensive care unit admission observed in this outbreak highlights the need for heightened clinical awareness and preparedness.