A powerful new synthetic opioid said to be more potent than fentanyl has been linked to dozens of recent deaths in the U.S., prompting warnings from health officials.
Tennessee was an early hotspot, with the state’s health department announcing in March that more than 30 fatal overdoses had been associated with cychlorphine since October 2025.
An April 2026 notice from the White House’s Office of National Drug Control Policy cited at least 41 Tennessee deaths between July 2025 and February 2026 and at least 55 deaths nationally.
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Fatal overdoses have also been reported in Illinois, California and Oklahoma, according to public health and law enforcement records.
“Cychlorphine is particularly dangerous due to its strength, where a very small amount can cause someone to stop breathing,” the Los Angeles County Department of Public Health said in its advisory.
Nicholas Kardaras, Ph.D., CEO and chief clinical officer of the New York Center for Living in Manhattan and a clinical professor at Stony Brook Medicine’s School of Social Welfare, called cychlorphine “the new fentanyl on steroids.”
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Cychlorphine is a novel, unregulated synthetic opioid that activates the same receptors as fentanyl, according to the Drug Enforcement Administration. It can cause profound sedation, slowed or stopped breathing, or death.
The drug is not approved for medical use and has been detected in illicit drugs and counterfeit pills.
Kardaras called cychlorphine “one of the most potent synthetic opioids” now appearing in the illicit drug supply.
“Fentanyl is about 50 times more potent than morphine or heroin,” he told Fox News Digital. “Cychlorphine is reportedly up to 10 times more potent than fentanyl — so theoretically, about 500 times more potent than morphine or heroin.”
“This new synthetic drug is making fentanyl look like yesterday’s candy.”
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Cychlorphine is taken in various forms — people can ingest it as a pill, snort it in powder form or crush it and administer it intravenously, according to Kardaras.
“The problem has been, in addition to its potency, it’s often put in other designer drugs and in counterfeit pills,” he cautioned.
While some people seek out cychlorphine for its potency, others may ingest it unknowingly when it is mixed into other substances.
“Sometimes, by talking about how potent some of these substances are, we increase the allure of them for some addicts, unfortunately,” Kardaras said.
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While cychlorphine is primarily a street drug, it can also be purchased online or via “boutique designer-drug markets,” according to the expert.
Cychlorphine can cause a fatal overdose in anyone, regardless of age. Kardaras said younger people may face greater exposure because some are more likely to experiment with drugs or purchase counterfeit pills.
“They’re buying something online … and all of a sudden, without knowing it, they’re ingesting fentanyl or another synthetic opioid,” he said.
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Naloxone, commonly sold under the brand name Narcan, can reverse cychlorphine’s opioid effects, but multiple or prolonged doses may be needed.
“What used to take one or two doses of Narcan to reverse an overdose may now require five or six doses, based on anecdotal evidence,” Kardaras said.
The DEA advises people to administer naloxone immediately, call 911 and be prepared to give additional doses.
Another major concern with cychlorphine is that standard fentanyl test strips and routine hospital opioid urine screens do not detect it.
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“Most drug tests have very specific chemical structures that they detect in any kind of synthetic or non-synthetic drug, and this new one hasn’t quite been baked into the current testing strips,” Kardaras noted.
The takeaway, he said, is that cychlorphine may be up to 10 times more potent than fentanyl, is not detected by standard fentanyl test strips or routine hospital opioid urine screens, and may require multiple doses of naloxone to reverse.
“So it’s a triple whammy,” he said. “It’s a constant battle of keeping up with the latest iterations of new drugs.”