Illicit veterinary sedative found in US drug supply

Health officials in the US are sharing that Zenalpha (medetomidine and vatinoxan hydrochlorides injection), a medication approved for dogs for sedation and analgesia and can be used under extra label drug use regulations for cats, pocket-pets, exotics, zoo and wildlife species for restraint and sedation, emerged as a dangerous adulterant in the illegal drug supply. Medetomidine, which received approval from the FDA in March 2022, is now often being mixed with other illicit drugs such as heroin and fentanyl.¹

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Illicit medetomidine was first identified in Maryland in 2022 and has now spread to California, Colorado, Illinois, Missouri, and Pennsylvania, with overdose clusters present in Chicago, Philadelphia, and Pittsburgh early 2025. Medetomine, which is a racemic mixture of dexmedetomidine and levomedetomidine, is not a controlled substance and was not approved for use in humans. Despite this, dexmedetomidine enantiomer is considered the pharmacologically active component that is responsible for the sedative and analgesic effects of the drug. Dexmedetomidine, which has separate approvals from the FDA for use in animals and humans, which is often used for sedation for humans in intensive care units.

Cases across the country

From May 11-17, 2024, Chicago, Illinois reported 181 suspected opioid overdoses in 3 hospitals, with 12 of them confirmed illicit medetomidine involved cases. Most patients exhibited slow heart rate, altered mental state, and a poor response to naloxone.²

Philadelphia reported 165 people were hospitalized with a previously unseen withdrawal syndrome that is now linked to illicit medetomidine between September 2024 and January 2025. Out of the patients that were hospitalized, most required and ICU visit and almost a quarter of them were intubated. For these patients, traditional treatments for opioid withdrawal treatments failed, dexmedetomidine was an effective way to control the patients symptoms due to the drug’s similar pharmacological properties to medetomidine.³

In Pittsburgh, almost 24 patients were evaluated between October 2024 and March 2025 with 10 confirmed to have illicit medetomidine exposure. Most of the patients ‘deteriorated rapidly’ prior to arriving at the hospital with symptoms including extreme autonomic hyperactivity, including agitation, hypertension, and tachycardia.⁴ Out of those 10 patients, 9 required ICU admission and all responded to dexmedetomidine when other medications did not work.

“This cluster of confirmed medetomidine-involved overdoses is the largest yet reported, and the landscape of adulterants in the illegal drug supply is ever-changing and expanding. The recent addition of xylazine has led to a concerning trend in deaths potentially resulting from adulteration in the fentanyl supply, and the emergence of medetomidine further complicates the opioid overdose crisis,” the CDC’s Morbidity and Mortality Weekly Report stated.

“Clinicians and persons who use illegal drugs should be aware that medetomidine can be present in the drug supply. Although medetomidine effects cannot be reversed with naloxone, if a person might be overdosing, the use of naloxone or any other opioid overdose reversal medication is recommended. In addition, connecting persons at risk for overdose to evidence-based treatment, services, and support can save lives,” it continued.²

References

1. Health officials finding different illicit veterinary sedative in US drug supply. News release. American Veterinary Medical Association. June 23, 2025. Accessed July 1, 2025. https://www.avma.org/news/health-officials-finding-different-illicit-veterinary-sedative-us-drug-supply
2. Nham A, Le JN, Thomas SA, et al. Overdoses Involving Medetomidine Mixed with Opioids — Chicago, Illinois, May 2024. MMWR Morbidity and Mortality Weekly Report. 2025;74(15):258-265. doi:https://doi.org/10.15585/mmwr.mm7415a1
3. Huo S, London K, Murphy L, et al. Notes from the Field: Suspected Medetomidine Withdrawal Syndrome Among Fentanyl-Exposed Patients — Philadelphia, Pennsylvania, September 2024–January 2025. MMWR Morbidity and Mortality Weekly Report. 2025;74(15):266-268. doi:https://doi.org/10.15585/mmwr.mm7415a2
4. Ostrowski SJ, Tamama K, Trautman WJ, Stratton DL, Lynch MJ. Notes from the Field: Severe Medetomidine Withdrawal Syndrome in Patients Using Illegally Manufactured Opioids — Pittsburgh, Pennsylvania, October 2024–March 2025. MMWR Morbidity and Mortality Weekly Report. 2025;74(15):269-271. doi:https://doi.org/10.15585/mmwr.mm7415a3