A sedative meant only for animals has turned up in San Diego County's illegal drug supply, prompting a warning from local officials about the overdose risks it poses to people who may not even know they're taking it. Medetomidine, a veterinary tranquilizer with no approved human use, was detected locally, and the county is urging caution as the drug's reach spreads nationwide.
No Human Use, But Already Circulating
The detection was first reported Thursday by CBS 8, which reported that medetomidine was found in San Diego's drug supply and that the county warned of overdose risk. Medetomidine's racemate is approved only for veterinary sedation and analgesia, with no human indication whatsoever, according to a study published in Springer Nature. That means anyone exposed to it is taking a substance designed exclusively for sedating animals, not people, often without knowing it's mixed into whatever drug they intended to use.
The physical effects can be severe. The same research describes medetomidine intoxication as causing more profound sedation, pronounced bradycardia, and hypotension compared with other sedatives sometimes found in street drugs. Coming off the drug isn't simple either, the study notes, since severe withdrawal can involve autonomic dysregulation, intractable vomiting, and encephalopathy that frequently requires intensive care.
A Drug That Spread Fast Elsewhere
Medetomidine isn't new to the national drug supply, even if its arrival in San Diego is a fresh concern. The Springer Nature research notes the drug was first detected in forensic samples in 2022 and spread across more than a dozen states within two years. By May 2024, at least 18 U.S. jurisdictions had confirmed medetomidine in their illicit drug supplies, according to a study in NEJM Evidence.
New York offers a glimpse of how entrenched the sedative can become once it takes hold. The same NEJM Evidence research found medetomidine first detected there on May 24, 2024, in a sample expected to be heroin. From May 2024 through December 2025, drug-checking programs in the state found medetomidine in 25.1% of all opioid samples tested, with a monthly peak of 44.1% in May 2025. New York City death certificate data identified 134 overdose deaths in which medetomidine was a contributing cause in 2025, up sharply from 18 the year before, per the same research.
San Diego's Overdose Numbers Have Been Improving
The medetomidine warning arrives even as San Diego County's broader overdose trends have been heading in a better direction. The county recorded 840 unintentional overdose deaths in 2025, an 11% decline from 945 such deaths the year prior, according to The San Diego Union-Tribune. That marked the fourth consecutive year of decline. The newspaper also reported that for the second year in a row, methamphetamine was involved in a larger share of overdose deaths locally than fentanyl.
None of the available reporting establishes whether medetomidine has contributed to any overdose or death in San Diego County specifically. The local detection itself has so far been reported only in the CBS 8 segment, without additional detail yet available on sample counts, concentrations, or where the drug was found.
What Officials Recommend
Because medetomidine often shows up mixed with opioids rather than on its own, standard overdose response guidance still applies. A CDC advisory notes that opioid overdose reversal medications, such as naloxone, should be administered to restore normal breathing in suspected overdoses, according to CDC Stacks. With medetomidine's spread already documented in other states and now reported locally, San Diego County residents who use drugs — or know someone who does — are being urged to stay alert to the possibility that what's being sold isn't what it seems.
