Background
The drug cartels have been cutting illicit fentanyl with xylazine for several years. Xylazine, also known as “tranq”, is a veterinary anesthetic that not only emphasizes the effect of fentanyl but also can cause severe muscular damage to tissues around or near the injection site. Several manufacturers have developed tests to detect the presence of xylazine, and this has helped community agencies manage drug overdoses.
The cartels have moved onto their next vice. They are now cutting fentanyl with another veterinary anesthetic, medetomidine1. Medetomidine is a more powerful veterinary anesthetic and poses a dangerous development in the fight against fentanyl1. Unlike xylazine, there are currently no rapid tests available to detect the presence of medetomidine in the drug supply1.
What is Medetomidine
Medetomidine, referred to as “rhino tranq,” is a veterinary anesthetic drug with potent sedative effects, increasingly being found mixed with fentanyl and xylazine, which further exacerbates the opioid crisis1. Medetomidine’s potency is 200-300 times greater than that of xylazine and makes opioid overdoses more difficult to reverse with naloxone. According to DEA Office of Forensic Sciences, xylazine remains the number one adulterant found in fentanyl powder, but the emergence of medetomidine is a dangerous development1.
Another form of the drug, its dextro-isomer dexmedetomidine (Dexdor®, Precedex®) is also utilized in human medicine2. Clinically, it is used to induce sedation, analgesia, anxiolysis, and muscle relaxation in both humans and animals2. Veterinary studies have shown medetomidine to be a more potent, selective, and specific agonist in the peripheral and central nervous systems than xylazine2.
Presence of Medetomidine3
In the past year, medetomidine-laced fentanyl has become a common element in overdoses in cities and states including Philadelphia, Chicago, and San Francisco. In Philadelphia, the presence of medetomidine in the drug supply went from 29% in May 2024 to 87% in November 2024. In this same period, the presence of xylazine dropped from 100% to 42%.
Medetomidine’s rapid proliferation throughout Pennsylvania’s drug supply happened soon after the state took action to crack down on xylazine. After temporarily classifying xylazine as a Schedule III controlled substance in 2023, the state made the measure permanent in May 2024, the same month Philadelphia health officials began testing for medetomidine.
The presence of medetomidine in the illicit US drug supply is rapidly increasing.
Effects of Medetomidine3
Medetomidine is causing severe health complications among people who use drugs, even compared to xylazine. Reports from doctors and public health officials indicate that overdose reversals, already made more difficult by xylazine, have taken on a new character with medetomidine, with low heart rates and “profound” sedation.
Withdrawal symptoms have taken on a new and potentially deadly wrinkle. While an overdose involving medetomidine often causes severe drops in heart rate and blood pressure, withdrawal from medetomidine causes the opposite effects – the nervous system skyrockets causing severely elevated heart rates and blood pressure that can damage organs including the heart and brain.
Like xylazine, medetomidine does not respond to naloxone, the common medication used to reverse opioid overdoses3. Unlike xylazine, medetomidine does not cause the tissue necrosis observed among users.
Implications for Public Health Practice4
The landscape of adulterants in the illegal drug supply is ever-changing and expanding. The addition of xylazine has led to a concerning trend in deaths potentially resulting from adulteration in the fentanyl supply. The emergence of the adulterant, medetomidine, further complicates the opioid overdose crisis. Clinicians and persons who use illegal drugs should be aware that medetomidine can be present in the community’s 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 help save lives
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References:
- https://www.dea.gov/sites/default/files/2025-05/2025%20National%20Drug%20Threat%20Assessment_Web%205-12-2025.pdf
- https://www.cfsre.org/images/content/reports/public_alerts/Medetomidine_Public_Health_Alert__Final.pdf
- https://www.statnews.com/2025/05/01/medetomidine-replacing-xylazine-in-fentanyl-increases-overdose-danger-withdrawal-risks/
- https://www.cdc.gov/mmwr/volumes/74/wr/pdfs/mm7415-H.pdf