The rise of nitazenes

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NICK EICHER, HOST: Coming up next on The World and Everything in It: monster opioids.

There’s a new wave of synthetic drugs that’re more powerful and deadly than fentanyl.

MARY REICHARD, HOST: They’re called nitazenes, opioids so dangerous they were never approved for human use. Today they are killing people across Europe.

And now they are trickling into the U.S. Experts warn there’s never been a more perilous time for those who abuse drugs.

EICHER: Here’s WORLD’s Anna Johansen Brown.

ANNA JOHANSEN BROWN: Robert Pennal served more than 24 years as a special agent with California’s Bureau of Narcotic Enforcement. Today he helps law enforcement stay up to date on trends in the illicit drug underworld.

ROBERT PENNAL: The first thing that really got our attention in the Central Valley was right around 2021-22, we started seeing colored fentanyl. Purple. Yellow. Silver. We had never seen that before.

Last year, California law enforcement partnered with the FBI to investigate a ring of Honduran drug traffickers. The traffickers were operating out of Merced County in the state’s central valley.

PENNAL: One of the things they find is that they offer Fetty, which is fentanyl, but they were also offering ISO.

ISO is the street name for Isotonitazene, which tends to be five to 20 times more powerful than fentanyl, though some is well over 40 times more potent. Law enforcement intercepted messages between a dealer and his customer discussing the deadly drug.

PENNAL: They talked about, first of all, you know that you know it was like it was a gray powder and had a kind of vinegar smell on it and they told them: hey listen you be really really careful because this stuff's really really powerful so you'd be careful using it. Well, the problem is the guy who is buying it says basically, "Don't worry about me. I know what I'm doing." Well, he didn't know what he was doing, see, and he overdosed and died.

Isotonitazene is one of at least eight different kinds of nitazenes. Scientists developed the class of opioids in the 1950s, around the same time as fentanyl. Researchers tinkered with the formula, hoping to create a different kind of opioid for managing pain—something with a chemical structure that was significantly different from morphine.

PENNAL: What they found was that nitazenes’ safety profile had real unacceptable side effects: respiratory depression and death. So it was never created.

But covert chemists operating underground began sifting through historical research for more ways to create synthetic opioids.

PENNAL: You have what are called patent pirates. And these are individuals that are always looking all over, whether it be on the dark web, whether it be all over open source material, they’re always looking for analog and new drugs, and they found nitazene, and they started reading about nitazene. You only have to have an organic chemistry background to make it.

Nitazenes exploded in the United Kingdom in 2023. There, at least 400 people died from nitazene-involved overdoses from July of that year to January 2025.

Some experts say the death toll is probably much higher than what’s officially documented since toxicology labs didn’t know what they were looking for or how to test for nitazenes when they first showed up.

Most individuals consume nitazenes thinking they are taking another substance. Here’s one British heroin user sharing his experience with a UK-based news podcast after he took a nitazene-laced version of the drug:

AUDIO: I had quite a big tolerance at the time and I just remember passing out basically as soon as I had it. And it just not tasting right, like it wasn’t right. I got a little bit and it instantly knocked me out. I couldn’t even stand up.

Nitazenes emerged in Europe after the Taliban began cracking down on Afghanistan's opium industry and heroin became harder to access.

Keith Humphreys is a drug policy researcher at Stanford University. He says the rise in synthetic opioids over natural opium comes down to money.

KEITH HUMPHREYS: Someone needs to harvest. Hope the weather holds, then you have to, you know, process it, export it past the border, get it on a boat, however many thousands of miles you're sending it to Europe or the U.S. or Canada or whatever, and there's risk of seizures all along the way. So that's a pretty expensive business model.

Creating and shipping synthetic opioids through the dark web eliminates many of those costs.

HUMPHREYS: Contrast that with making fentanyl or a carfentanil or a nitazene, which can just be done in a lab, close to the source of where the customers are. So the production cost is probably 1 % to make a synthetic opioid as heroin. And as a result, that over time is inevitably going to force heroin out.

Unauthorized chemists also tweak drug formulas to evade government regulations. More than 80 fentanyl-related substances have been reported to the United Nations Office on Drugs and Crime. Here’s Robert Pennal again.

PENNAL: We just had a recent seizure that involved carfentanil. Carfentanil is an extremely powerful opiate that is used by veterinarians to anesthetize elephants and rhinos. In big zoos, we use carfentanil.

Pennal said Mexican cartels are becoming more deeply embedded in Canada, where they are turning their attention to producing incredibly dangerous synthetic opioids.

PENNAL: One of the most popular ways to purchase or ingest fentanyl is these counterfeit oxy blue M30 pills. But we had a batch show up in Idaho that were all nitazene.

Law enforcement raided two large labs in Canada last year that were producing nitazene pills.

PENNAL: It's literally following the same track as fentanyl.

Fentanyl killed nearly 73,000 Americans in 2023. Overdose deaths are now starting to decline thanks in part to the widespread availability of the anti-overdose drug naloxone. But nitazene overdoses are even more difficult to reverse than fentanyl or heroin.

PENNAL: You have the reversal drug naloxone and you get a powerful opiate like nitazene where before it might have taken four to eight milligrams or two dosages of naloxone. Now it may take four.

Pennal says there’s never been a more risky time to experiment with drugs.

PENNAL: The problem you run into now is everything is either diluted or it's cut with or it's in combination with different drugs. One of the big things you'll get from people is that, "Well, really, Bob, they don't want to kill all their customers." Well, that's not true at all anymore. There are so many millions of customers and people, they don't really think like that, you know, that they don't want to kill off their customers. It's just all about making money.

I’m Anna Johansen Brown with reporting from Addie Offereins.

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