People gather outside the Savage Sisters’ community outreach storefront in the Kensington neighborhood of Philadelphia. The area is being hit hard by Medetomidine and Xylazine, powerful sedatives most often used by veterinarians that are moving through the illicit drug supply triggering “mass overdose” events and causing gruesome skin wounds. (AP Photo/Matt Rourke)

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Public health officials say Mexican cartels and drug gangs inside the U.S. are mixing a dangerous chemical sedative called medetomidine into fentanyl and other drugs sold on the street. The combination triggered a new wave of overdoses that began in late April and have accelerated in May.

“The numbers reported out of Philadelphia were 160 hospitalizations over a 3 or 4-day period,” said Alex Krotulski who heads an organization called NPS Discovery that studies illicit drugs sold in the U.S.

Medetomidine, most often used by veterinarians as an animal tranquilizer, but also formulated for use in human patients, has also been linked to recent “mass overdose outbreaks” in Chicago and Pittsburgh.

Experts say the chemical, mixed into counterfeit pills and powders sold on the street, slows the human heart rate to dangerous levels. It’s impossible for drug users to detect.

Public health advisories have been issued in Illinois and Pennsylvania.

Dr. Brendan Hart at Temple University in Philadelphia says they first began hearing reports of street drug users exposed to the fentanyl-medetomidine mix in April.

“Some of our emergency medicine doctors started stopping me in the hallway,” Hart told NPR.

“They said ‘Something funny is going on with the overdoses.’ Patients were coming in with very low heart rates. As low as in the 20s. A normal heart-rate is sixty to a hundred [beats per minute] so 20s is extremely low.”

Laboratory tests of street drug samples came back positive for the powerful sedative, which is used in some formulations by doctors with human patients, but only in carefully controlled medical settings.

Medetomidine was previously detected in the illicit drug supply as early as 2022 but only rarely and in small amounts. This time experts say it appears to be spreading rapidly, with large-scale overdose events also reported earlier this year in Toronto, Canada.

US drug supply grows more toxic

Last year the Biden administration issued a warning that street fentanyl was being mixed with another tranquilizer used by veterinarians called xylazine. That mix of drugs led to more overdoses and many users also experience terrible flesh wounds that can linger for months or years.

Medetomidine is even more powerful than xylazine, experts told NPR. As it spreads, Krotulski said no one knows what long-term health effects this new cocktail of chemicals will cause in the human body.

“Patients are being cared for as we speak in emergency rooms,” he said. “These are very complex drug products. You’ve got fentanyl adulterated with xylazine that now also contains medetomidine.”

Registered nurse Kathy Lalli treats Ellwood Warren’s injuries at the Kensington Hospital wound care outreach van, parked in the Kensington neighborhood of Philadelphia, Tuesday, May 23, 2023. In humans, xylazine can cause breathing and heart rates to drop. It’s also linked to severe skin ulcers and abscesses, which can lead to infections, rotting tissue and amputations. Experts disagree on the exact cause of the wounds, which are much deeper than those seen with other injectable drugs. (AP Photo/Matt Rourke)

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The presence of these chemical additives severely complicates the medical response to high-risk overdoses.

Xylazine and medetomidine don’t respond to naloxone, the medication used to reverse most fentanyl overdoses. There’s currently no way for street users to know when their drugs are laced with this chemical.

Dr. Bertha Madras, a drug researcher at Harvard Medical School and McLean Hospital, said it’s not clear why drug gangs are mixing these new chemicals with fentanyl. Some experts believe sedatives may prolong the opioid high, making the drugs more desirable on the street.

According to Madras, it’s urgent that first responders and emergency rooms be prepared to treat overdoses complicated by heart conditions triggered by medetomidine.

She also thinks people using drugs need to be warned that illicit pills and powders are more perilous than ever.

“It’s critical to alert street users,” Madras said. “They’re playing Russian roulette now with the drug supply.”

Madras said experts are also working to understand where the medetomidine appearing on U.S. streets is coming from.

It’s not yet clear whether the sedative is being illegally diverted from veterinarian supplies or from medications intended for use in hospitals and clinics.

It’s also possible drug gangs are formulating their own medetomidine compounds from precursor chemicals acquired illegally.

Evolving street drug supply outpaces public health, law enforcement

Madras said Mexican cartels and U.S. drug gangs are moving fast to create new combinations of powerful synthetic drugs, often using chemicals like medetomidine which aren’t yet regulated or tightly controlled under U.S. law.

She said it’s nearly impossible for US law enforcement and public health to keep up.

“There is an almost endless supply of new psychoactive substances and there are literally thousands and thousands of drugs that can be made,” she said.

Experts say the decision to experiment with xylazine, medetomidine or other chemicals in illicit street drug combinations likely reflect which substances are cheap, poorly regulated and readily available.

Some critics, including Dr. Jeffrey Singer, a drug policy analyst at the libertarian Cato Institute, believe law enforcement efforts aimed at regulating chemicals used in street drugs are actually encouraging the cartels to experiment with more readily available substances that may be more harmful, including medetomidine.

“Law enforcement is trying harder and harder to crack down on xylazine,” Singer said. “If the drug trafficking organizations are interested in adding a sedative [to their street drug mixes] they can always add medetomidine.”

Singer believes interdiction of synthetic drugs is so difficult that U.S. policy-makers should focus resources on helping drug users find medical treatment instead of funding more law enforcement efforts.

Efforts to tightly regulate medetomidine could be complicated by the fact that a version of the sedative called dexmedetomidine is widely used by physicians as well as veterinarians.

“That medicine is used everywhere along the lifespan, from [neonatal intensive care units] to sedate babies that need to be on respirators, to elderly patients who can’t breathe on their own,” said Dr. Nabarun Dasgupta, a street drug expert at the University of North Carolina at Chapel Hill.

“[Restricting access to] medetomidine like xylazine or even fentanyl will have major impact on every hospital in the country,” he said.

Fatal overdoses in the U.S. dropped 3 percent last year, but roughly 107,000 people in the US still died after using street drugs.

Addiction experts worry modest gains in saving lives of drug users could be reversed as more toxic chemicals like medetomidine and xylazine hit the streets.