Xylazine, a drug used to sedate large animals, has been linked to an increasing number of overdose deaths across the country. The drug, also known as “tranq,” “tranq dope” and “zombie drug” is being used to cut heroin, fentanyl and other illicit drugs, says the New York Post. And its side effects can be horrifying ─ it can literally rot a user’s skin.

The Food and Drug Administration approved xylazine, a non-opioid, for veterinary use. It is not safe for humans and, frighteningly, those who overdose do not respond to naloxone, or Narcan, the most common overdose reversal treatment.

Xylazine results in excessive sleepiness, slows breathing and heart rate, and causes raw wounds that can become severe and spread quickly throughout the body, says the Post. The crusty ulcerations, which can turn into dead skin called eschar, may result in amputation if untreated.

The drug is hitting big cities across the country, especially Philadelphia, New York, and Los Angeles. In Philadelphia, 90% of lab-tested dope samples from 2021 contained xylazine, which increases the risk of overdose when combined with other illegal substances. According to Insider, Philadelphia is regarded as ground zero for the drug, and it has traveled to the west, infiltrating California’s drug trade. Xylazine is used to cut the opioid fentanyl to lower dealer costs and extend the effects of the drug.

Dr. Gary Tsai, the director of substance abuse prevention and control with the Los Angeles County Department of Public Health, believes the drug’s prevalence “would increase deaths from overdoses.”

“The main concern is that we’re already amid the worst overdose crisis in history, nationally and locally,” Tsai told the Los Angeles Times.

Experts say that xylazine extends the high enjoyed by opioid users, but that the skin-rotting side effects kill any pleasure associated with the drug.

“Tanq is basically zombifying people’s bodies,” said one 28-year-old user, according to a graphic investigation by Sky News. “Until nine months ago, I never had wounds, now there are holes in my legs and feet. Just cleaning them is painful.”

The interviewed user says that although he has been in treatment for his addiction “at least seven times,” he hasn’t “been able to detox off tranq. It’s the mixture of it all, the fentanyl with the tanq.”

Incidences of xylazine overdose are concerning because it is not an opioid, said Dr. Ponni Arunkumar, the chief medical examiner of Cook County in Illinois. “It does not get affected by naloxone, which is used to reverse a fentanyl overdose,” she added.

The situation in Philadelphia is so bad that one expert, Andrew Best, the chief of Philadelphia’s Substance Use and Prevention and Farm Reduction program, says right now there is no state or federal funding available to mitigate some of the challenges associated with xylazine.

“A lot of individuals have never seen these wounds before,” he told Sky News. “They don’t heal as fast as a normal wound. Sometimes they can last for months, even years, and in severe cases require amputations. I don’t want this to spread to other cities. But I also want other cities to be able to learn from what we’re doing.”

According to a 2022 report, xylazine has been detected in 36 states, says the Post. In New York City alone, the drug was found in 25% of the drug samples. The San Francisco Department of Health reported that they discovered low levels of xylazine in the systems of four people who overdosed, which means the substance may be hidden in other drugs.

“It’s possible that it’s more out there,” warned Tsai.