Testing strips for xylazine, the animal tranquilizer contaminating Philly’s drug supply, could be coming to the city soon

When the powerful animal tranquilizer xylazine began appearing in opioids sold illegally on the street in Philadelphia several years ago, many people who use opioids had almost no way to know what was happening to their drugs.

Xylazine, known as tranq, can cause serious wounds and overdoses that aren’t easily reversed with naloxone, a medication used to reverse opioid overdoses. And there were no options available to screen for xylazine on the street — just lab tests that didn’t have much real-time utility for people actively using drugs.

People in addiction commonly use testing strips to identify the presence of fentanyl, a deadly synthetic opioid involved in Philadelphia’s soaring rate of overdose deaths. Now, a Canadian company is manufacturing xylazine testing strips, which research from Philadelphia’s health department and a local lab has found to be effective in detecting the tranquilizer on the street.

The strips, made by the Ontario-based biotechnology company BTNX, work similarly to a COVID-19 antigen test. A drug is dissolved in water, and the test, a long strip of paper, is dipped in. As the water soaks the strip, it activates a control line to indicate that the test is working and then activates a second line to indicate the presence of xylazine.

Fentanyl testing strips work the same way. Neither test can show the amount of fentanyl or xylazine in a given substance — just their presence.

Philadelphia Deputy Health Commissioner Frank Franklin said the department is planning to purchase and distribute xylazine testing strips “in the near future.”

“The hope is that we’ll avoid some overdose-related events, whether fatal or nonfatal,” he said.

Philadelphia saw its highest-ever number of fatal overdoses in 2021, with 1,276 deaths. Fentanyl was present in 94% of deaths involving opioids and 77% of all overdose deaths. Xylazine was present in 34% of all deaths — a 39% increase from the year before.

Fentanyl — cheaper, more potent, and easier to transport than heroin — began replacing heroin in the city’s drug supply in the mid-2010s. But it has a shorter half-life than heroin, meaning people addicted to it must use more often to avoid painful withdrawal symptoms. Health officials believe xylazine was initially added to fentanyl to give it “legs” — a longer-lasting high.

Because xylazine is not an opioid, people who use opioids laced with it are at risk for overdoses that are harder to treat with naloxone, the opioid overdose-reversing drug. As with fentanyl, many drug users become dependent on xylazine unintentionally.

The new tests are effective in finding xylazine at fairly low concentrations, lower than what is typically seen in street drugs, said Alex Krotulski, the associate director at the Center for Forensic Science Research & Education (CFSRE), who conducted the research on the strips. He and city health department officials used the strips to test 34 samples of illicit drugs whose chemical makeup they already knew — some with xylazine and some without.

The strips did turn up a few false positives. But, crucially, they did not produce any false negatives — in other words, an indication that there was no xylazine in a drug sample that actually contained it.

“I have a lot of confidence from what we’ve seen so far that these strips will be effective,” Krotulski said.

The city’s department has partnered with CFSRE since 2020, testing dozens of drug samples purchased on the streets. So far, nearly every sample of purported “dope” — a catch-all term the department uses to describe powders sold as heroin or fentanyl — has also contained xylazine.

The lab’s work has helped city officials better understand the city’s changing drug supply and issue warnings to drug users. The testing strips will now help people who use drugs to run checks on their own, allowing them to understand what’s in their drugs in real time.

In Pennsylvania, state legislators last year legalized the possession of all drug testing strips. (Other states have legalized only fentanyl testing strips.)

BTNX has priced xylazine strips at $200 for a box of 100 strips. Fentanyl testing strips cost $100 for a box of 100 strips.

BTNX’s CEO, Iqbal Sunderani, said the company hopes to similarly bring the price of xylazine strips down in the next three to six months. He learned about xylazine’s emergence in the United States last year at a trade show, he said.

“We moved quickly to try to put these strips in the hands of people who are using the drug,” he said. “They know the problems it causes.”