Science

FDA warns of risks from an animal drug xylazine linked to overdose in humans

The Food and Drug Administration issued an alert Tuesday warning health care professionals to be “alert” of an animal drug that has entered an illegal drug supply and an overdose has been identified.

The drug, xylazine, is FDA-approved for use as an animal sedative and pain reliever. It has no approved use for humans and “can cause serious and life-threatening side effects that are similar to those commonly associated with opioid use.”

In a letter to stakeholders, the FDA stated that xylazine was often found in combination with opioids such as: fentanyl or heroin, or sometimes with stimulants such as methamphetamine or cocaine. The administration warned that people who have been exposed to xylazine “may not know” that it is present in their drug supply.

Alert warned that it can be “difficult to differentiate” xylazine overdose from opioid overdose, as some of the side effects are similar, including respiratory depression.

Routine toxicology screens also do not detect xylazine. Other side effects may include hypothermia, hypotension, and “severe, necrotic skin ulceration” caused by repeated exposure to xylazine via injection.

Despite similar side effects and presentation, xylazine affects the human body differently than opioids.

“Xylazine sets out in a really wide way,” said Claire Zagorsky, a paramedic and program director and harm reduction instructor with the Texas Opioid Training Initiative at the University of Texas at Austin. “It lowers brain activity, slows down the heart rate, slows down breathing, but opioids have this special aspect to them where they can really stop breathing. Xylazine does exactly that. …we’re not seeing the kind of sudden fatal overdoses we’re seeing with fentanyl.”

The FDA said it is uncertain whether side effects from xylazine exposure can be reversed by naloxone, a drug that can reverse opioid overdoses, because xylazine is not an opioid.

“(Xylazine overdoses) are almost certainly not reversible with naloxone,” Zagorsky said, adding that just one study has suggested naloxone to work to reverse such overdoses. The study was conducted in chicks in 1984.

Zagorsky also cautioned that fentanyl test strips, which can check illegal substances for the presence of potent opioids, do not work with xylazine. Test strips for xylazine are in development, according to Jeffrey Bratberg, a clinical professor at the University of Rhode Island College of Pharmacy.

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