Xylazine, an animal tranquilizer, is latest threat in the opioid epidemic: What you need to know

A new threat has emerged in the United States' illicit drug supply: an animal tranquilizer called xylazine.

The drug is showing up in synthetic opioids, particularly fentanyl, leading to more overdoses and alarming side effects, according to the White House Office of National Drug Control. 

While most jurisdictions don't routinely test for xylazine in postmortem toxicology, the Drug Enforcement Administration estimates xylazine was involved in at least 1,281 overdose deaths in the Northeast and 1,423 in the South in 2021. 

Last week, ONDC director Dr. Rahul Gupta hosted a listening session with local public health and safety leaders to discuss trends related to xylazine and efforts to address it, including plans for tracking, substance use treatment, and harm reduction.

Here’s what to know about the animal tranquilizer and why health officials are rushing to stop its spread.

What is xylazine? Is it a horse tranquilizer?

Xylazine was created in the 1960s and is used in veterinary medicine to sedate animals during procedures or diagnostic testing, according to the DEA.

Xylazine is not approved by the Food and Drug Administration for human use.

While it has been given in the past for household pets, the sedative is now typically used for larger animals like horse, sheep and elk. 

It's most commonly used in cattle as it's one of the few sedatives studied in food animals, said Dr. Bernd Driessen, professor of anesthesiology at the University of Pennsylvania School of Veterinary Medicine. 

The drug is available in liquid form and sold in vials or preloaded syringes in veterinary medicine, the DEA said, but it can also be sold online in powder form.

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Xylazine side effects include open wounds

Anecdotal reports indicate using xylazine causes open wounds to "spontaneously develop," said Maryann Mason, associate professor of emergency medicine at Northwestern University Feinberg School of Medicine. 

These open wounds may lead to necrosis, or dead tissue, and eventually amputation of affected limbs, she said. 

Xylazine is not an opioid and doesn't target the same receptors, but the Michigan Poison Center at Wayne State University says it has similar effects, including: 

• Sedation
• Anesthesia
• Muscle relaxation
• Slowed respiratory rate
• Slowed heart rate

The poison center said xylazine can be swallowed, snorted, injected, smoked or inhaled. The DEA said it's unclear whether it can be vaped. 

Is xylazine safe? What should you do if someone overdoses?

There is no amount of xylazine that is safe for humans, said Dr. Neeraj Chhabra, emergency medicine physician and medical toxicologist at Cook County Health in Chicago. 

Humans are about 10 to 20 times more sensitive to xylazine than animals are, Driessen said. 

The sedative can be lethal because it slows down breathing, Mason said, like an opioid overdose. However, because the animal tranquilizer is not an opioid, an overdose can't be reversed by naloxone, known as Narcan. 

"Xylazine is not responsive to naloxone like heroin and fentanyl are," Chhabra said. Medical providers "may have to provide certain support measures in addition to naloxone," like breathing assistance. 

An antagonist that reverses the sedative effects of xylazine, called atipamezole, is used in veterinary medicine. While it has been studied in humans, it is not approved for humans by the FDA, said Driessen. 

In the event of a suspected overdose, the National Institute of Drug Abuse still recommends giving naloxone because xylazine is frequently combined with opioids. As with all overdoses, the agency also urges calling emergency medical services. 

Where is xylazine showing up?

In an October report, the DEA said exposure to xylazine is most common amongst people who use heroin, fentanyl or cocaine.

The administration said xylazine is commonly found in drugs that have two or more substances present. While some users actively seek substances with xylazine, others are surprised by the adulterated supply.

'Zombie' drug? Other names for xylazine

Brand names for xylazine include:

• Rompun
• Sedazin
• AnaSed

In the illicit drug market, providers have heard xylazine or drugs laced with xylazine referred to as:

• Tranq
• Tranq Dope
• Sleep Cut
• Zombie Heroin

The drug was also called "anestesia de caballo," or horse anesthetic in Spanish, in Puerto Rico where it was first noted as an adulterant in the illicit drug supply in the early 2000s, according to the DEA report.

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Follow Adrianna Rodriguez on Twitter: @AdriannaUSAT. 

Health and patient safety coverage at USA TODAY is made possible in part by a grant from the Masimo Foundation for Ethics, Innovation and Competition in Healthcare. The Masimo Foundation does not provide editorial input.