Powerful synthetic opioids stronger than fentanyl were found in several overdose deaths in Philly

The Philadelphia Medical Examiner’s Office found that powerful synthetic opioids called nitazene analogues were present in at least five overdose deaths in Philadelphia in the last two years, and suspects that the emerging threat contributed to a dozen more overdose deaths.

Nitazenes are a class of drugs up to 40 times more powerful than fentanyl, another synthetic opioid much stronger than heroin that is behind most of Philadelphia’s overdose deaths. A record 1,413 people died from overdoses involving any illicit drugs in 2022, the latest year for which complete data are available.

The overdose deaths involving nitazenes show how the illegal drug market in Philadelphia is becoming even more toxic. Since a nitazene analogue was first detected in drug samples collected by the city health department in December 2022, health officials here have worked to determine how widespread these drugs are in Philadelphia’s drug supply.

In a health alert released last month, city officials told medical providers that they had detected a number of nitazene analogues in overdose victims since December 2022. It’s difficult to say exactly how many people have died of nitazene-related overdoses since they first turned up in the city, said Daniel Teixeira da Silva, the medical director of the city health department’s division of substance use prevention and harm reduction.

That’s because several different types of nitazenes have been detected in drug samples in the city, and it’s not clear how many are circulating in the drug supply, making it difficult to know which to look for in a toxicology test. (Philadelphia’s medical examiner has begun testing for nitazene analogues in overdose deaths. Many communities do not test for these drugs at all, Teixeira said.)

The health department suspects that a nitazene analogue known as N-desethyl isotonitazene was present in 12 overdose deaths in Philadelphia between November and December 2022. Two other nitazene analogues were identified in an overdose victim who died in June 2023. And since December 2023, a fourth analogue has been found in four people who died of overdoses and two people with other “traumatic causes of death,” the health department says.

In some of these cases, overdose victims were also found to have taken fentanyl, xylazine, and other drugs. It’s unclear whether those drugs were combined by dealers and sold together, health officials say, or whether victims combined them knowingly.

But all of the toxicology results point to a volatile and unpredictable drug supply that is contributing to rising overdose deaths in the city.

“It’s really this continuing trend of when you’re using dope that you’ve bought off the street, you really don’t know what you’re using,” Teixeira said. “We have stronger synthetic opioids and multiple sedatives in these samples.”

Once known for its pure, cheap heroin, the city’s illicit opioid supply was first contaminated by the synthetic opioid fentanyl, up to 50 times more powerful than heroin, in the mid-2010s. Soon fentanyl had largely replaced heroin in the city’s illicit opioid market.

Around 2019, xylazine, an animal tranquilizer that is not an opioid but has similar sedative effects, began to turn up in fentanyl. Xylazine causes intense withdrawals, overdoses that are harder to treat, and gaping flesh wounds that can become blackened as they turn necrotic.

Now health officials say that nitazene analogues are adding new dangers to the drug supply. Like fentanyl, nitazenes can be produced in a lab. Since they’re opioids, nitazene overdoses can be treated with the overdose-reversing drug naloxone. But because they’re so powerful, a typical dose of naloxone might not be enough to revive a person overdosing on nitazenes.

Drug users who have taken nitazenes have also reported intense withdrawal symptoms that come on more quickly — which can prevent people from seeking treatment even when they’re hoping to quit. Often in Philadelphia, people looking to enter inpatient treatment must first go through an intake process that can take hours and sometimes days, researchers at Jefferson University Hospital found in a recent study.

Faced with the intense pain of a fentanyl, xylazine, or nitazene withdrawal, many people are unable to wait that long.

“Someone who’s dependent on a very toxic drug supply has a very small window in which they feel well enough to even consider treatment,” Teixeira said. “It’s really a vicious cycle, and this just makes it worse.”

Nitazenes are not easily detectable outside of a lab — there are test strips that can detect fentanyl and xylazine on the street, but nitazene testing strips are rare. Teixeira said that people who use illicit drugs should be aware of the potential that they could be taking nitazenes unknowingly.

No one should use drugs alone, he said. For years, the city has recommended that everyone should carry naloxone regularly so they can act quickly if they encounter someone overdosing. “We have to continue to saturate the city of Philadelphia with naloxone and make sure that everyone’s educated,” Teixeira said.