Nitazenes, a class of synthetic opioids, have spread through the U.S. illicit drug supply in recent years, drawing warnings from drug monitoring agencies about their extreme potency and overdose risk.
The opioid class was first identified in the U.S. street drug supply in late 2019 and early 2020, according to the Inter-American Drug Abuse Control Commission. The U.S. is recognized as a global epicenter of the opioid epidemic, with robust substance use surveillance systems that have helped track the drugs’ emergence.
In March 2026, Missouri’s Department of Health and Senior Services, Department of Public Safety, Department of Elementary and Secondary Education, and Department of Mental Health alerted residents to the drug’s growing presence statewide, as detections rose across wastewater monitoring, law enforcement surveillance and overdose investigations.
Here are eight things to know:
1. Nitazenes were developed by researchers about 60 years ago as an alternative to morphine but were never released for medical use because of their high overdose potential. Also known as benzimidazole opioids or new psychoactive substances, common nitazenes include isotonitazene, metonitazene, etonitazene and protonitazene. At least 13 types of nitazenes have been identified.
2. The drugs are typically sold as a white powder, crystalline solid, or brown or yellow powder, and have also turned up in tablets misrepresented as oxycodone, as well as in heroin, ketamine and synthetic cannabinoids. Nitazenes can be used by injection, inhalation or orally in tablet form.
3. Potency varies widely across the drug class but is often extreme. Fentanyl is generally 25 to 50 times stronger than heroin, which is roughly twice as strong as morphine. The most common nitazene, isotonitazene, is estimated to be 250 to 900 times stronger than morphine. The most potent nitazene identified so far is up to 4,300 times stronger than morphine, per the commission’s bulletin.
4. Short-term effects can include euphoria, relaxation, drowsiness, clumsiness, pain relief, reduced stress, itchiness, nausea, vomiting, fever, sweating, and slowed breathing and heart rate.
5. Because of their potency, an overdose may require multiple doses of naloxone to reverse. Many people encounter nitazenes unintentionally, mixed into other substances, so they and those around them may not realize additional doses are needed.
6. The U.S. Drug Enforcement Administration classified isotonitazene as a Schedule I substance under the Controlled Substances Act in 2020. Seven other nitazenes have since been scheduled the same way. Nitazenes have also turned up in U.S. wastewater testing, including a 2022 to 2023 study that found protonitazene in samples from Washington and Illinois.
7. Long-term effects haven’t been studied enough to fully understand the risks, but nitazenes are believed to carry a high potential for tolerance and dependence, similar to other opioids. Reports from people who use the drugs suggest withdrawal is comparable to severe opioid withdrawal, with effects that can include excessive sweating, restless legs, fever, dizziness, flu-like symptoms, anxiety and panic attacks.
8. Missouri has emerged as a state-level example of the trend. Nitazenes have been detected in 26 of 37 participating Missouri schools since January, and the state recorded 14 nitazene-related overdose deaths in 2024 — more than triple the total recorded from 2019 through 2023 — according to a March 24 news release from the Missouri Department of Health and Senior Services. Officials noted that standard drug tests don’t detect nitazenes, complicating identification and response, and that the drugs have been found in counterfeit pills, illicit powders, unregulated cannabis products and vape liquid.
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