A horse tranquilizer is increasingly appearing as a street drug in the United States and is now involved in nearly a third of fatal opioid overdoses in Philadelphia, according to a new study.
The tranquilizer drug, called xylazine, is not considered an opioid, but it is often found mixed with opioids heroin or fentanyl, a combination sometimes known as a “tranquilizer drug”, according to the study published Tuesday (February 2) in the newspaper Injury Prevention.
The researchers found that the drug’s detection during post-mortem examinations has increased dramatically in the past decade among people who died of opioid overdoses in Philadelphia.
The findings suggest that “the opioid epidemic in the United States continues to evolve,” wrote the authors. They say that overdose deaths involving xylazine may be underreported in the country because laboratories do not always test. The authors call for greater monitoring of xylazine abuse in the U.S., as well as its health consequences.
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Animal tranquilizer
Xylazine is a sedative used in veterinary medicine, especially in horses. In the USA, it is not approved for use in humans and is known to cause potentially dangerous side effects in people, including low blood pressure and a decrease in heart rate.
Illegal drug users in Puerto Rico have been taking xylazine with opioids since the early 2000s and, more recently, appeared in the supply of illegal drugs in the continental health departments of the United States in Maryland, Ohio and Michigan all reported several cases of overdose deaths involving xylazine in the past two years. But overall, research on xylazine in the US supply of illegal drugs is very limited.
In the new study, the researchers analyzed data on overdose deaths in Philadelphia from 2010 to 2019. Specifically, they examined unintended deaths involving heroin or fentanyl, which are both types of opioids.
They found that, between 2010 and 2015, xylazine was detected in only 2% of these overdose deaths. But in 2019, that number jumped to 31%.
Furthermore, US Drug Enforcement Administration data on illegal drug seizures suggests that xylazine is increasingly appearing in samples of “polypharmaceuticals” that contain heroin or fentanyl along with other drugs. Between 2010 and 2013, none of the polypharmaceutical samples tested in the agency’s laboratories contained xylazine, but in 2019, 25% contained the drug.
Studies on the effects of xylazine in combination with opioids are limited, but some research suggests that the mixture may increase the risk of opioids overdose death.
Still, the researchers note that their study failed to determine which drug or drug combination was involved in overdose deaths in Philadelphia.
It is also unclear exactly why xylazine is being added to the United States’ drug supply and whether people who have overdosed are known to have taken the drug. Some focus groups in Philadelphia have found that people who use illegal drugs report that xylazine makes opioid effects last longer, the authors said.
The authors concluded that “further studies are needed to understand the synergistic effects of
use of fentanyl and xylazine by humans and to better contextualize the reasons for their use in the USA. “And whenever possible, health jurisdictions should do consistent testing for the drug, they said.
Originally published on Live Science.