MADISON, Wis. — Health officials and researchers are warning about cychlorphine, a synthetic opioid being linked to overdose deaths in several parts of the country and described by the Office of National Drug Control Policy as potentially up to 10 times more potent than fentanyl. Cody Wenthur, an associate professor at the University of Wisconsin-Madison School of Pharmacy, said less than a milligram may be enough to cause a fatal overdose — an amount smaller than the tip of a pencil. The drug may be mixed into other illicit substances or pressed into counterfeit pills designed to resemble prescription medications. That means people may be exposed without knowing which substance they are taking. Public Health Madison and Dane County said there is currently no evidence that cychlorphine is present in the Madison area. Wenthur cautioned, however, that the illicit drug supply can change quickly, making it difficult to predict when a new substance could appear. “Once something enters the marketplace, it’s hard to predict how quickly those negative consequences are going to add up,” Wenthur said. “So being prepared is better than being reactive.” Standard fentanyl test strips do not detect cychlorphine, according to the report. Wenthur said naloxone, commonly known by the brand name Narcan, can reverse an overdose involving the drug, although more than one dose may be needed. Anyone administering naloxone should also call 911. Gina Malagold, director of multicultural affairs at the national organization Song for Charlie, said families and young people need continuing, practical information about counterfeit pills and the broader unpredictability of the drug supply. Song for Charlie data indicate that the share of teenagers aware that fentanyl can be found in counterfeit pills has increased from 27% in 2021 to 65%. But the perceived risk remains uneven: 33% of teens consider a pill from a close friend highly dangerous, compared with 88% for a pill from a stranger. The organization also found a gap between parent and teen conversations about pill misuse. While 73% of parents said they had discussed the issue with their children, only 27% of teens recalled having that conversation. Teens identified fear of judgment or an extreme reaction as the main reason they might not speak up. About seven in 10 teens said stress and anxiety are major reasons their peers misuse pills, while younger teens ages 13 and 14 reported less awareness of the risks than older teenagers. Malagold said the specific drug may change, but the danger of unknowingly taking a contaminated or counterfeit pill remains. That makes access to naloxone, emergency response and nonjudgmental education important even in communities where cychlorphine has not been detected.