Opioid addict Martin has seen the deadly fentanyl replace heroin as the most prevalent drug in New York. Now he's trying to avoid "tranq," a flesh-eating drug increasingly causing concern across America.
"It makes holes in your body, your skin," said the 45-year-old, whose wounds on his legs and arms signify he may have unknowingly injected the animal sedative, officially named xylazine and commonly called the "zombie drug."
The tranquilizer, approved for veterinary use by the US Food and Drug Administration (FDA), has infiltrated the illegal drug market in the United States, with producers increasingly using it to augment fentanyl.
Overdose deaths where tranq was detected have soared in recent years and in April the White House designated the drug an "emerging threat."
"It eats up your flesh, like a crocodile," Martin, who did not wish to give his surname, told AFP during a visit to St. Ann's Corner of Harm Reduction, a drug-support and syringe-exchange center in the Bronx.
Xylazine is easily accessible on the internet and almost always coupled with fentanyl, the synthetic opioid 50 times more potent than heroin.
Fentanyl pushed the number of fatal overdoses in the United States to nearly 110,000 in 2022, a record.
According to the Centers for Disease Control and Prevention (CDC), the estimated number of overdoses involving xylazine in the country rose from 260 in 2018 to 3,480 in 2021.
While Philadelphia is the epicenter of tranq use, the drug is also gaining ground in New York. City authorities say traces of xylazine were found in 19 percent of fatal opioid overdoses, around 419 deaths, in 2021.
"Fentanyl is a short-acting opioid so people have to use more frequently," to prevent withdrawal, explained Courtney McKnight, clinical assistant professor of epidemiology at New York University's School of Global Public Health.
"The thinking is that xylazine has been added to the supply because it can extend the life of fentanyl. However, there are other side effects that come with it that are pretty significant," she added, citing anxiety.
Health experts also suspect that xylazine causes abscesses and skin ulcers by tightening blood vessels. In some cases, it can lead to amputation.
Workers at St. Ann's are seeing more skin wounds when they're on streets of the Bronx to provide treatment, equipment, clean syringes, fentanyl tests, food and, sometimes, just a few words of advice and comfort.
"A lot of times people say that they show up like little bruises or black marks," said Jazmyna Fanini, a nurse at the center. But then "the tissue dies around that area."
"I've been seeing them a lot more. They can get really bad sometimes, even down to the bone," she added.
The number of fatal overdoses in New York soared more than 80 percent between 2019 and 2021 to 2,668 deaths, largely due to fentanyl as well as the COVID-19 pandemic, which isolated users and hampered relief efforts. African-American and Hispanic communities were the most impacted.
Both the city and drug-prevention associations are focusing on naloxone, a nasal spray antidote that reverses an opioid overdose. But xylazine is not an opioid, so naloxone does not reverse its effects.
Law enforcement is hamstrung by the fact that the sedative is not legally classified as a "controlled substance".
"Even if we found a big stash of it, you wouldn't be able to prosecute somebody for that," New York's special narcotics prosecutor, Bridget Brennan, told AFP.
That means "we can't track it back to the source. We can't find out how it's being distributed in large amounts," she added
At St. Ann's, where each leaf of a paper tree stuck to the wall represents a loved one lost to drugs, the emergence of these new blends of drugs is considered the result of policies that criminalize drug users.
"You're going to continue to find all of these different types of substances in the supply until we address the real issue, which is just not having a safe supply," said team leader Steven Hernandez.
"The challenge is just simply that people are really being poisoned," he added.
The center is taking part in a city-wide program that encourages users to test their drugs before taking them. The initiative should enable health services to monitor developments in the illegal drug market in real time.
Leonardo Dominguez Gomez, a field researcher with New York's health department, said it is still possible to avoid xylazine because it hasn't proliferated through the market.
"How the city decides to do public health campaigns will impact that," he told AFP.