Street drugs with a KUH tranquilizer: The FDA warns that cocaine, meth and heroin are adulterated with the deadly animal tranquilizer “xylazine.”

Americans are being warned that a dangerous animal tranquilizer may be lurking in illegal street drugs.

The Food and Drug Administration (FDA) has issued a warning about xyxine appearing in a growing number of toxicology reports after fatal overdoses.

Xylazine is not approved for human use and is widely used in veterinary medicine as a sedative or pain reliever for cows and horses.

The FDA warns that it can cause “serious and life-threatening side effects similar to those commonly associated with opioid use” in humans.

Nevertheless, xylazine is increasingly being used by drug dealers as a filler in heroin, meth, cocaine and opioids, the federal agency said in a letter to those involved on Tuesday.

The warning warned that it “can be difficult to distinguish a xylazine overdose from an opioid overdose” — both drugs cause the lungs to begin to fail.

But unlike opioids, xyxine overdose cannot be mitigated with naloxone, the opioid reversal rescue drug.

The animal narcotic is becoming increasingly common in heroin and some stimulants such as cocaine and meth. Because it is not an opioid, its effects cannot be mitigated with the opioid overdose reversal drug naloxone.

So far this year, 68 xylazine poisoning cases have been reported to US poison control centers. More than half of these incidents were intentional and the result of self-harm or substance abuse.

Xylazine should not be confused with the popular hallucinogen ketamine, which was originally developed as a tranquilizer for horses.

While national figures on xylasin are murky — the drug can only be detected with advanced drug screening — several alarming trends are being reported.

It is implicated in up to 20 percent of overdose deaths in hard-hit states, including Massachusetts, Connecticut, Illinois and Pennsylvania.

Xylazine — sold under the brand name Rompun in the U.S. — first became popular in the 2000s in Puerto Rico, where it is known as “Anestecia de Caballo.”

It has become a widely used adulterant for heroin, a cheap way for drug dealers to improve the drug’s absorption and increase its potency.

In Puerto Rico, xylazine is most commonly found in a drug combination nicknamed “speedball,” which consists of heroin and cocaine and is used to balance the effects of both the low and the high.

A 2008 study found that more than 90 percent of the syringes used for fastballs tested from Puerto Rico contained xylazine.

Public health officials were alerted in part because of the appearance of sores on the skin of users where they injected the drug.

The painful lesions are often exacerbated when users repeatedly inject at the same site, hoping to benefit from the opioid’s pain-relieving effects.

The drug made its mark in Philadelphia, home to the largest open-air heroin drug market on the East Coast.

Between 2010 and 2015, xylazine was detected in 40 of Philly’s 1,854 accidental overdose deaths (just two percent) with evidence of heroin and/or fentanyl.

Since then, the prevalence of xylasin in Philadelphia has increased significantly.

It was detected in 10 percent of fentanyl and/or heroin overdose deaths in 2017, 18 percent in 2018 and 31 percent in 2019.

In 2020, xylazine was present in nearly 26 percent of overdose deaths in Philadelphia, followed by about 19 percent in Maryland and 10 percent in Connecticut.

The FDA’s warning to healthcare professionals included a warning that the non-opioid drug’s effects cannot be mitigated with naloxone, the rescue drug used to reverse an opioid overdose.

The FDA stated, “Health care professionals treating opioid overdose should consider xylasin exposure when patients do not respond as expected to naloxone administration or when signs or symptoms of xylasin exposure (eg, unusual skin necrosis) are present.”

Health officials are now concerned that the drug is migrating west. Xylazine overdoses have also been recorded in Cook County, Illinois, Harris County, Texas, Jefferson County, Alabama, Milwaukee, Wisconsin and the state of New Hampshire.

The rise in the drug’s prevalence suggests that the ongoing crisis of overdose deaths is far from over.

The overdose epidemic has been exacerbated by the Covid pandemic, which has forced people to quarantine early and keep their distance from others, leading to feelings of isolation and despair.

Severe movement restrictions imposed in early 2020 further limited treatment options for people in recovery.

The number of fatal drug overdoses rose 15 percent to more than 107,000 in 2021, equaling the previous record from the previous year.

The synthetic opioid fentanyl caused more overdoses than any other drug and led to more than 71,000 deaths, a 23 percent increase from the previous year.

Fatal cocaine-related overdoses are up 23 percent through 2021, while methamphetamine overdose deaths are up 34 percent.