GREENSBURGH, Pa. (PIX11) — Before xylazine, the horse tranquilizer, exploded into the national consciousness — because of horrifying street scenes in Philadelphia — police in western Pennsylvania were dealing with a different kind of animal drug in the narcotics supply.

“We started seeing what’s called carfentanil,” said Detective Justin Scalzo of the Greensburg Police Department, located about 45 minutes east of Pittsburgh. “Carfentanil is commonly used as an elephant tranquilizer. And now we’re seeing an additive with fentanyl known as xylazine.”

Xylazine is known as “tranq” on the streets, and it’s been called an “emerging threat” by the White House when it’s mixed with the opioid fentanyl. Fatal overdose rates tied to mixes of xylazine and fentanyl skyrocketed more than 1,000% in the southern United States in 2021.

There’s a key difference between xylazine and carfentanil. Carfentanil is a synthetic opioid, like fentanyl, that can respond to the antidote Narcan, or naloxone, in reversing a potentially fatal overdose.

Xylazine is not an opioid, so it doesn’t respond to Narcan. Drug users are in danger of fatally overdosing from xylazine, or tranq, because it also suppresses breathing and the heart rate like fentanyl does. Still, doctors recommend using Narcan if you suspect any kind of overdose, because fentanyl is often involved in the mix.

Greensburg is located in Westmoreland County, Pennsylvania. The county coroner, Tim Carson, said xylazine was present in more than half the fatal overdoses this year so far.

“This year, right now, we have 15 confirmed overdoses, and eight have xylazine in them,” Carson told PIX11 News inside the morgue. “Xylazine definitely factors in to bringing their heart rate down. It definitely slows everything down.”

One of the overdose victims in December was Deanna Poska, a 31-year-old mother of two children whose heroin addiction turned into a fentanyl addiction. She had been sober four months when she died during a relapse. A large amount of xylazine was cut into the fentanyl dose she fatally overdosed on.

“If they’re using too much of the xylazine cut, they almost ‘crash,'” the coroner said.

Carson believes the xylazine doses are coming in from places like New York City, a hub for the drug trade in the Northeast.

Detective Scalzo noted the people preparing the doses are not professional chemists.

“The people mixing this aren’t rocket scientists,” Scalzo said. “These are street dealers that are mixing it. They are cutting their product to make it more powerful. And the more powerful they make it, the more customers they’re going to have.’

Doctors in Philadelphia pointed out IV drug users there are now doubly addicted: to tranq and fentanyl. Withdrawal symptoms from tranq (xylazine) can be brutal.

“Managing the withdrawal symptoms, you have to manage them in parallel to fentanyl as well,” said Dr. Frank Franklin, deputy commissioner of the Philadelphia Department of Public Health.

PIX11’s Mary Murphy has been covering the rise of animal tranquilizers mixed with illegal drugs like fentanyl and heroin for months. PIX11 News will air a half-hour special, Tranq: The Zombie Effect, on Thursday, April 27, at 7 p.m.