Los Angeles County has recorded its first death from cychlorphine, a synthetic opioid more potent than fentanyl that standard test strips cannot detect.

The Los Angeles County Department of Public Health announced the fatality Oct. 15, saying the county Medical Examiner identified cychlorphine as a cause of a February 2026 overdose death. The confirmation marks the first time the drug has been found in the local illicit supply.

Cychlorphine, also known as N-propionitrile chlorphine, can cause someone to stop breathing in very small amounts, the department said. Unlike fentanyl, it does not show up on fentanyl testing strips. It is being mixed into street drugs without users' knowledge.

The drug has appeared in powders, counterfeit prescription pills, rocks, crystals and liquids, according to county officials. It was first detected in the U.S. illicit supply in 2024 and has since been identified in 19 states. A separate cychlorphine-related death was reported in Northern California in April 2026.

The Drug Enforcement Administration (DEA) classified cychlorphine as a Schedule I controlled substance in August 2026, making it illegal to possess or sell. The U.S. Food and Drug Administration (FDA) has never approved it for medical use.

The overdose risk rises sharply when cychlorphine is combined with alcohol, sedatives, painkillers or other drugs, the health department said.

County officials urged residents who use drugs to carry naloxone, which can reverse an opioid overdose and restore breathing. Multiple doses may be needed. Naloxone nasal spray is available at county Community Health Stations, public health centers, retail pharmacies and medical providers.

Anyone who suspects an overdose should call 911 immediately and administer naloxone, officials said.

While fentanyl test strips will miss cychlorphine, a free drug-checking program at drugcheckingla.com can detect it, with results in about 15 to 20 minutes, the health department said.

County officials said cychlorphine has been more common in other parts of the country but that they are now monitoring the local supply for signs it is spreading.

Residents seeking substance use treatment can call the county Substance Abuse Service Helpline (SASH) at 800-854-7771 or visit RecoverLA.org.