An animal tranquilizer poisoning the heroin supply has drug policy experts worried

Xylazine is contaminating the drug supply, causing grisly injuries and death

By Troy Farah

Science & Health Editor

Published September 25, 2022 2:00PM (EDT)

Empty xylazine bottle found on the streets of Philadelphia (Christopher Moraff / Narcomedia)
Empty xylazine bottle found on the streets of Philadelphia (Christopher Moraff / Narcomedia)

A tranquilizer used for animals is appearing more frequently in street drugs across North America, alarming drug policy experts and harm reduction advocates alike. Xylazine may sound like the name of a "Star Trek" character, but it's actually a muscle relaxer widely used in veterinary medicine – and it's causing big problems across the continent.

Xylazine has found its way into what used to be the U.S. heroin supply but is now almost entirely illicit fentanyl, a powerful opioid that can be 100 times more potent than morphine. Xylazine is not an opioid, but it can knock a user out for longer than most opioids – about six to eight hours – thus playing a growing role in drug overdose deaths, according to experts.

When injected, the mixture of xylazine and fentanyl, sometimes called "tranq dope," can also produce grisly injuries, such as lesions or open skin ulcers. Because they can be extremely painful, some individuals who use drugs will continue to inject into these open sores and wounds for relief. However, that can make things worse, causing the wounds to necrotize, or essentially rot on the body, often requiring amputation. Sometimes, it can even result in death.

Unfortunately, experts aren't entirely sure why xylazine seems to be causing these injuries, which also has made them difficult to prevent. Worse, there aren't good drugs for reversing a xylazine overdose. With fentanyl, it's at least possible to stop a deadly overdose using naloxone, a drug that replaces any substances clogging opioid receptors in the brain. With xylazine, naloxone seems to have little effect, though it should still be administered as a precaution, experts advise.

"The harms of xylazine are compounded when it is used in combination with other central nervous system depressants like alcohol, benzodiazepines and opioids (like fentanyl or heroin), which can increase the risk of fatal overdose," Dr. Nora Volkow, the director of the National Institute on Drug Abuse, told Salon in an email. "Xylazine is one component of the severe current overdose epidemic, and we must work to make treatment for substance use disorders cheaper and easier to obtain than illicit drugs."

Xylazine is approved for use in animals — it's particularly useful for getting cats to vomit — but because it can lower blood pressure and heart rate, the U.S. Food and Drug Administration hasn't approved the drug for use in humans. This is the first time that Claire Zagorski, a licensed paramedic, program coordinator and harm reduction instructor for the PhARM Program at the University of Texas, has seen a veterinary drug diverted into human use in such a manner. 

"The lingering health effects are worse than any acute overdose effects," Zagorski told Salon. "The really nasty wounds are truly the worst that I've seen. I'm getting a lot of reports of people that are having rhabdomyolysis, [which is] really bad kidney injury from muscle breakdown and nerve damage. I've had people that have lost a leg because they're nodding out on a stoop or something, bent way over with their head in between their knees for like 20 hours. [Xylazine] also f**ks with blood sugar and causes anemia — and we don't know why."

"No one knows what this is," she added. "There are no experts in xylazine use in humans. There isn't a single goddamn one."

Some people appear to like xylazine because of the way it interacts with opioids, potentiating the high. Unlike heroin, which has "legs," fentanyl can be short-acting, requiring multiple doses throughout the day. While Xylazine can stretch out the high, many injection drug users aren't seeking it out due to the risks. Instead, they're accidentally ingesting it.

Want more health and science stories in your inbox? Subscribe to Salon's weekly newsletter The Vulgar Scientist.

It's not clear why it keeps appearing, but illicit xylazine use isn't entirely new. As far as anyone can tell, the intentional use of xylazine first became widespread in Puerto Rico in the early 2000s, where it is known as "anestesia de caballo," or horse anesthesia.

For many years, a program has existed called Air Bridge, in which some Puerto Ricans who use drugs are lured to Philadelphia under the false promise of addiction treatment. Instead of entering a posh rehab, these victims are often extorted by those running the programs designed to help them while being subjected to emotional and physical abuse.

"People who are basically sent here under this false promise of getting 'help,' and then stuck here with no resources," Dr. Megan Reed, an assistant professor in the Department of Emergency Medicine at Thomas Jefferson University in Philadelphia, told Salon. "I think anytime you bring people over, culturally, people's preferences are also going to be brought over."

This crossover may explain why xylazine was detected in street drugs in Philadelphia before most other U.S. cities. Between 2010 and 2015, xylazine was detected in less than 2% of cases of fatal opioid overdoses in the Pennsylvania city. By 2019, that number had risen to 31%. Last year, when the Philadelphia Department of Public Health analyzed samples of fentanyl sold on the street, it found that 91% contained xylazine, making it the most common adulterant in the local drug supply.

But now xylazine is appearing in drugs in far more cities across North America, including regions in California, Colorado, Connecticut, Illinois, Massachusetts, New York, North Carolina and British Columbia, Canada.

"I see tons of xylazine, from all over the country," Dr. Nabarun Dasgupta, a pharmaceutical scientist at the University of Carolina at Chapel Hill, told Salon.

Dasgupta's work includes running a drug-checking service that uses analytical chemistry to detect the ingredients in street drugs. Samples are mailed to Dasgupta from across the country, which he and his team run through a gas chromatography-mass spectrometer, providing a window into the contaminates that individuals who use drugs unwittingly consume.

"The bottom line is the drug supply is so f**ked right now . . . It's a really dangerous time to be doing unregulated drugs."

"The bottom line is the drug supply is so f**ked right now," Dasgupta said. "There's no consistency, and things are changing. So, it's a really dangerous time to be doing unregulated drugs."

As part of her research into overdose prevention, Reed began interviewing a group of people who had overdosed on crack cocaine. She asked if they would be willing to use fentanyl test strips on their stimulants, which are tiny sticks of paper that can detect if the illicit opioid is present. The strips can help people who use drugs make informed, consensual decisions about their drug use. The individuals interviewed by Reed spontaneously started to ask about test strips for xylazine.

"The concern that they expressed most often was about the heavy sedating effect of xylazine and not liking it," Reed said. "One thing that I haven't really heard talked about is the risks for women who use drugs and being heavily sedated for a long period of time, who might be vulnerable to being victimized and robbed when they're sedated."

After being asked about xylazine test strips, Reed in turn began to ask more people if they would use them. While her sample size was only 13, all of the individuals were interested, according to her analysis, which was published this month in Drug and Alcohol Dependence Reports.

Another study published earlier this year in Clinical Toxicology that reviewed dozens of reports of xylazine poisoning concluded: "The development of a real-time detection test would greatly improve the prevention, diagnosis, management and/or outcomes of patients with accidental or intentional xylazine ingestion."

But such a product doesn't currently exist, and according to Volkow, it's not clear if one is even being developed. There isn't a way to tell if xylazine is contaminating illicit substances outside of services like those offered by Dasgupta, which aren't widespread despite their utility in reducing overdose harms.

Part of the reason for xylazine's growing presence could be that the drug isn't scheduled under the Controlled Substances Act, meaning the tranquilizer is far less regulated than most pharmaceuticals. The U.S. Drug Enforcement Administration (DEA), which is responsible for scheduling substances under federal law, declined to comment for this story.

"Because xylazine is not a controlled substance, its regulation does not fall under the purview of DEA."

"Because xylazine is not a controlled substance, its regulation does not fall under the purview of DEA," a spokesperson said via email.

Aside from releasing a one-page factsheet in February 2021, the DEA doesn't seem to have done much else to warn the public about xylazine. It has, however, sounded the alarm about "rainbow fentanyl" being marketed to children (though it has yet to produce hard evidence of such).

Of course, even if xylazine were to be scheduled, it's far from guaranteed that it would disappear from the streets. After all, illicit cocaine, fentanyl and methamphetamine are all readily available, as indicated by the ever-rising tide of overdose deaths in the U.S.

"Frustratingly, there's a whole class of drugs that are related to xylazine that could be pivoted to if xylazine gets a crackdown," Zagorski said. "There's a whole bunch that are all used as sedatives in the veterinary side. So, we'll see what comes up next."

In the meantime, experts are still trying to figure out the best way to respond to a growing crisis. There are a few ways people who use drugs can reduce the harms associated with xylazine.

"Because of the sedating effects of xylazine and drug mixtures containing xylazine, individuals should never use drugs alone and should start with small doses and use slowly," Volkow said. "Always carry naloxone in case of overdose (opioids may knowingly or unknowingly be present in the drugs an individual is using). If available in your area, have your drugs tested for xylazine at a harm reduction organization."

According to Volkow, the grisly injuries associated with xylazine can quickly become serious health problems.

"Monitor injection sites or other wounds and get prompt medical care for abscesses or skin ulcers," she advised. "Many harm reduction programs offer wound care kits as well."

If you suspect someone is overdosing on xylazine, giving them naloxone is recommended, as opioids are also likely to be present. Furthermore, there's some evidence that naloxone can reverse a xylazine overdose, even though xylazine largely acts on different receptors in the body than opioids.

Naloxone can reverse a clonidine overdose, and xylazine is an analog of clonidine, meaning they share some of the same features. It seems, however, that higher doses of naloxone may be required to work on xylazine, which complicates matters. Naloxone is so powerful that using it can send someone with opioid dependence into immediate withdrawal, which can be deeply uncomfortable. 

A higher dose of naloxone may reverse a xylazine overdose, but that means greater withdrawal symptoms, which can encourage riskier drug use. "When they do wake up, they're going to be in such severe withdrawal that they're going to go use in a way that's putting them at higher risk for overdosing again," Reed explained.

"What we need is legislation passed to make it explicitly legal for people to do drug checking work, and we need the federal government to endorse overdose prevention sites," Reed added. "Because if somebody is using xylazine in an overdose prevention site, then they have a safe place to be while they're sedated. Like we always say, never use alone. If we had overdose prevention centers, that would at least be another option for somebody to go into."

Reed also called for more research, as did Zagorski.

"We need people on labs sorting out why this is happening – and that takes years" Zagorski said. "By the time we have answers, xylazine probably won't be an issue anymore. So, we're just in a situation where the process of learning and discovery is too out of step with what is actually happening on the ground."

By Troy Farah

Troy Farah is Salon's science and health editor specializing in drug policy and pandemics.

MORE FROM Troy Farah

Related Topics ------------------------------------------

Drug Overdoses Drug Policy Fentanyl Harm Reduction Xylazine