Surveillance data first detected the sedative medetomidine in New York state in mid-2024, and through 2025 it was identified in 25.1% of opioid samples analyzed, with a monthly peak of 44.1% in May 2025, according to a Public Health Alerts report published today.
Medetomidine is a synthetic alpha-2 adrenoreceptor agonist that can cause prolonged sedation and a complex withdrawal syndrome that can complicate community and clinical responses to overdose and substance use care. The drug also contributed to 152 overdose deaths in 2024 and 2025, the report authors say.
Public Health Alerts, a new collaboration between NEJM Evidence and CIDRAP, fills a gap in reliable data, offering expert-reviewed reports that translate frontline observations into actionable public health evidence. An NEJM Evidence editorial explains the initiative further.
134 medetomidine-related overdose deaths in 2025
The report outlines all samples with secondary laboratory results available from May 2024 to December 2025 in New York, as well as New York City postmortem toxicology data to identify the role of the drug in fatal overdoses.
On May 24, 2024, medetomidine was first detected in New York via laboratory testing of a sample expected to be heroin collected in an upstate county, which produced unexpected sedative effects. State officials collected additional samples containing medetomidine the following month that were involved in two nonfatal overdoses.
Officials then alerted medical examiners about the presence of medetomidine in the illicit drug supply, which helped establish a drug standard and development of a postmortem toxicology test. Systematic postmortem toxicology testing for medetomidine began in October 2024 in New York City.
After months of laboratory detection in less than 10% of opioid samples, medetomidine skyrocketed in the illicit drug supply, with a jump to over 20% of collected opioid samples by October 2024 and into 2025. From May 2024 through December 2025, 25.1% of total included opioid samples contained medetomidine, with a monthly peak of 44.1% of samples in May 2025.
Death certificate data in New York City revealed medetomidine as a contributing cause of 18 overdose deaths in 2024 but 134 such deaths in 2025. But the authors note, “Cause and manner of death for all cases in 2024 and 2025 are not finalized; additional cases may be identified as investigations continue.”
They conclude, “Collaborative efforts in New York led to timely identification of this emergent substance and enabled overdose prevention responses, prioritizing harm reduction services and rapid dissemination of information to public and clinical audiences.”