While the dangers of fentanyl have been dominating headlines for years, the death toll from another class of extremely potent synthetic opioids called “nitazenes” has been climbing steadily. For decades, knowledge of nitazenes — also called benzimidazole opioids — was limited to those researching opioid pharmacology, but that all changed in 2019, when the drugs emerged on the illicit street drug market — first in Europe, then in the United States. While it started out in eight countries, it had spread to 19 by 2022. According to the United Nation Office on Drugs and Crime’s World Drug Report 2025, nitazenes’ presence on the illegal drugs market have been increasing for the past five years, and represents a growing threat to public health. But it’s unclear how nitazenes entered the world’s drug supply to begin with, as there has never been public demand for the drugs.
The major concern is with nitazene overdose deaths. This is, in part, because isotonitazene — the most common nitazene, also known as “ISO” — is five to nine times stronger than fentanyl, which itself is generally 25 to 50 times stronger than heroin, which is about twice as strong as morphine. All that is to say that less than 2mg of ISO — the equivalent of the tip of a pencil or a few grains of sand — can kill you, says Brian Townsend, a retired supervisory special agent with the Drug Enforcement Administration (DEA) and founder and president of Only 2mg Inc., a nonprofit addressing the use of fentanyl and other emerging illicit substances.
At this point, there are limited data on the number of nitazene deaths in the United States. The closest thing we have are the findings of two studies, though neither could provide detailed estimates of the scope of nitazene deaths globally, and are likely undercounts of the extent of nitazene overdose in the Americas. The first found that nitazenes played a role in at least 200 overdose deaths in Europe and North America from 2020 to 2021. The second found 93 fatalities in 2022 from eight case reports primarily from the United States.
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Here’s what to know about nitazenes, why they’re taking off, and their implications on public health.
What are nitazenes?
Nitazenes are a class of potent synthetic opioid created in the 1950s as an alternative to morphine, but never approved for medical use because of their potential for overdose, Townsend tells Rolling Stone. Fentanyl was created during the same period, he adds.
“They are unrelated to opioids derived from morphine or fentanyl, but function similarly by acting on opioid receptors to cause effects like analgesia, euphoria, sedation, respiratory depression, and even overdose and death,” says Ryan Marino, MD, a toxicologist and expert in addiction medicine at University Hospitals in Cleveland.
Nitazenes come in many forms, including pills, powders, and sprays — both in “pure” form and mixed with other drugs like heroin, fentanyl, and benzodiazepines. Nitazenes can be ingested intravenously, intranasally, orally, sublingually, and by inhalation (vaping).
Nitazenes work by binding to the opioid receptors to stop or reduce the intensity of pain, just like heroin, fentanyl, or other opioids, Townsend explains. “The problem is they are super strong, and they slow down the part of your brain that tells you to breathe,” he explains. “This is what causes respiratory depression. We sometimes refer to this as the ‘sleepy death.’”
In the U.S., clonitazene and etonitazene — two types of nitazenes — were included in the original Controlled Substances Act of 1971 as Schedule 1 drugs, which have a high potential for abuse, and don’t currently have an accepted medical use. In 2020, the DEA classified isotonitazene as a Schedule 1 substance, and since then, seven other nitazenes have been similarly scheduled.
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Despite being illegal, enforcing the law is difficult. “The chemicals that make up nitazenes are fairly inexpensive and also easy to access and inexpensive to make the drug, causing it to become more prevalent in communities worldwide,” says Jessica Steinman, chief clinical officer at No Matter What Recovery in Los Angeles.
It’s also difficult to get accurate numbers demonstrating the scope of the problem because we can’t reliably detect nitazenes. “Standard fentanyl test strips don’t pick up nitazenes, and most hospital toxicology panels don’t include them, which means overdoses get misidentified and deaths are underreported,” says Jason Bernstein, LMFT, detox/residential and dual diagnosis outpatient clinical director at Clear Behavioral Health. “For people managing addiction this is destabilizing, because harm reduction strategies fall apart when you can’t test for the most dangerous thing in the supply.”
According to Marino, it’s unclear why nitazenes entered the drug supply in the first place, and people do not seek them out, nor has there been known demand for them. “They may be a response to efforts to reduce the supply of other opioids, and even other drugs like benzodiazepines,” he tells Rolling Stone. “In almost every case where nitazenes are found, they are added to other drugs, primarily fentanyl, and not advertised as containing nitazenes when sold.” Between 2019 and 2023, nitazenes have been identified in at least 4,300 law enforcement drug seizures in the United States.
Though we don’t have a complete picture of nitazene deaths, we do know that they’re taking place across the country. For example, a study conducted in 2022 and 2023 found nitazenes in wastewater samples from Washington and Illinois. The Ohio Department of Health reported seven nitazene-related overdose deaths in the state in 2020, followed by an average of 57 deaths in 2021 and 2022, and 77 in the first six months of 2023.
While there weren’t any nitazene-related deaths in Tennessee in 2019, there were 92 between 2020 and 2023. Most of the overdoses also involved fentanyl. Additionally, the Pennsylvania health department has reported at least 50 fatal overdoses associated with nitazenes since 2020, with a record 29 deaths in 2024.
Similar to other opioids, naloxone can reverse a nitazene overdose. However, because of the potency of nitazenes, multiple doses of naloxone may be needed.
According to Justin Gurland, a licensed master social worker specializing in addiction, there isn’t a particular demographic that’s intentionally seeking out nitazenes. “That’s part of what makes them so dangerous,” he tells Rolling Stone. “Most people taking them don’t even know they’re taking them. Nitazenes are being mixed into heroin, counterfeit pain pills, and even non-opioid drugs, so they’re reaching people who never set out to use an opioid in the first place.”
Why are nitazenes taking off?
Nitazenes are becoming increasingly popular because they’re inexpensive, strong, and addictive, Townsend says. “They’re cheap, so drug traffickers ‘cut’ their drug supply and make more money,” he explains. “They are powerful, enhancing or intensifying the drug high. I’ve had a lot of people who struggle with substance abuse tell me they seek this out [for] the stronger highs. Finally, they’re addictive, which means repeat customers and more money for the drug traffickers adding these poisons to their supply.” And because of nitazenes’ potency, “doses can be very small, which makes them easy to hide or transport from place to place,” Steinman tells Rolling Stone.
Many experts believe that nitazene analogues may have entered the recreational drug markets to replace fentanyl analogues after the enactment of class-wide fentanyl analogue bans in China and the United States, says Marthe M. Vandeputte, a researcher in the laboratory of toxicology at Ghent University in Belgium.
On July 1, 2025, China implemented a generic ban targeting nitazene analogues. “This means that, with one scheduling order, the large majority of nitazenes known to date has been made illegal in China, which is known to be the main production country,” Vandeputte tells Rolling Stone. “Given China’s important role in the production of nitazenes, we expect that this may have a significant impact on the new synthetic opioid market in the upcoming year, as fewer new nitazene analogues may enter the markets.” But she says that we may see the appearance of other classes of synthetic opioids instead.
“In addition, the 2022 Taliban-imposed ban on opium poppy cultivation may impact the heroin supply in Europe and elsewhere, which may further fuel the rise of synthetic opioids such as nitazenes,” she says.
Why are people concerned about nitazenes?
More than 20 different nitazene variants have emerged since 2019, and new ones keep appearing. “As soon as one compound gets scheduled, manufacturers tweak the molecule slightly and produce something that’s technically not illegal yet,” Bernstein says. “What started in heroin has now spread to stimulants, depressants and counterfeit pharmaceuticals. If you’re buying any street drug right now you’re potentially at risk.”
For Luke Archibald, MD, section chief of addiction psychiatry at Dartmouth Hitchcock Medical Center in New Hampshire, all the unknowns surrounding nitazenes are concerning — especially because they’re made up of a group of chemicals with potentially different properties, like varying potencies and responses to naloxone. “It is worrisome to not know what may be contained in any given supply, and there are reports of nitazenes contained in counterfeit pills that may be marketed as other substances and ingested by opioid-naïve individuals,” he tells Rolling Stone.
Nitazenes’ potency is also troubling. “Even a trace amount — a dose small enough to fit on the tip of a pin — can slow or stop breathing,” Gurland says. “And the difference between a ‘dose’ and a fatal overdose can be microscopic.”
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According to Gurland, the biggest concern is that most people using them don’t know they’re using them, because nitazenes are showing up in counterfeit pills and powders, mixed into what looks like oxycodone, heroin, or even non-opioid drugs. “For people already living with addiction, that unpredictability makes every use potentially lethal. It’s not just about potency — it’s about invisibility,” he explains. “They’re hard to detect, and labs often don’t test for them. That’s why they’re being called the next wave in the synthetic opioid crisis.”
Like fentanyl, nitazenes are quickly becoming a public health issue. “That combination of strength and stealth is what makes them so dangerous,” Gurland says. “People don’t know what they’re taking, first responders don’t always know what they’re dealing with, and standard drug tests can even miss them. So you have this invisible risk spreading through communities that are already stretched thin by the opioid crisis.”
