A new synthetic opioid called cychlorphine, reportedly far more potent than fentanyl, has been linked to dozens of overdose deaths across several states, including Tennessee, Illinois, California and Oklahoma.
Tennessee’s health department reported in March that more than 30 fatal overdoses had been associated with cychlorphine since October 2025. A White House Office of National Drug Control Policy notice issued in April 2026 put the Tennessee death toll at 41 between July 2025 and February 2026, with at least 55 deaths reported nationwide.
The Los Angeles County Department of Public Health has also issued a warning about the drug. “Cychlorphine is particularly dangerous due to its strength, where a very small amount can cause someone to stop breathing,” the department said in its advisory.
How It Compares to Fentanyl
Cychlorphine is an unregulated synthetic opioid that acts on the same receptors as fentanyl, according to the Drug Enforcement Administration. It is not approved for any medical use and has turned up in illicit drug supplies and counterfeit pills.
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, described cychlorphine as “the new fentanyl on steroids.”
“Fentanyl is about 50 times more potent than morphine or heroin,” Kardaras 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.”
The drug can be taken as a pill, snorted as a powder, or crushed and injected, Kardaras said. It is sold mainly on the street but also appears online through what he called “boutique designer-drug markets.”
Because it is often mixed into other substances, people may ingest it unknowingly. “The problem has been, in addition to its potency, it’s often put in other designer drugs and in counterfeit pills,” Kardaras said. He also cautioned that publicizing a drug’s strength can backfire. “Sometimes by talking about how potent some of these substances are, we increase the allure of them for some addicts, unfortunately,” he said.
Who Is at Risk
Cychlorphine can cause a fatal overdose in anyone, Kardaras said, but younger people may face greater risk because they are more likely to experiment with drugs or buy counterfeit pills without knowing what they contain. “They’re buying something online … and all of a sudden, without knowing it, they’re ingesting fentanyl or another synthetic opioid,” he said.
Treatment and Detection Problems
Naloxone, sold under the brand name Narcan, can reverse cychlorphine’s effects, but it may take far more than the usual one or two doses. “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 recommends administering naloxone immediately, calling 911, and being ready to give additional doses.
Standard fentanyl test strips and routine hospital opioid urine screens do not detect cychlorphine. “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 said.
He summed up the danger as a “triple whammy”: cychlorphine may be up to 10 times more potent than fentanyl, it evades standard testing, and it may require multiple doses of naloxone to reverse. “It’s a constant battle of keeping up with the latest iterations of new drugs,” he said.
