Los Angeles County Confirms First Fatal Overdose From Cychlorphine

Los Angeles County health officials warned Thursday that a synthetic opioid called cychlorphine has caused the county's first confirmed fatal overdose, after the county Medical Examiner's Office identified the drug as a cause of death. The death occurred in February, according to the Los Angeles County Department of Public Health, and marks the first confirmed presence of cychlorphine in the county's illicit drug supply.

Cychlorphine, also known as N-propionitrile chlorphine, is more potent than fentanyl and can cause severe respiratory depression and death, the department said. Officials cautioned that even a small amount can cause a person to stop breathing and that the drug cannot be detected by fentanyl test strips.

What the county told residents

The department said cychlorphine may be mixed into illicit drugs without the user's knowledge, raising the risk of an unintentional overdose, and that the danger grows when the drug is combined with alcohol, sedatives, painkillers or other substances. The county said a separate cychlorphine death was reported in Northern California in April.

"The safest course of action is to avoid using illicit substances, given the possibility of the presence of cychlorphine," health officials said in the alert. They urged residents to carry naloxone, the overdose-reversal medication that can restore breathing during an opioid overdose, including one involving cychlorphine, and noted that multiple doses may be necessary. Naloxone is available as a nasal spray or an injection through county Community Health Stations, public health centers, retail pharmacies and medical providers.

The county also pointed residents to a free drug-checking program that can test samples specifically for cychlorphine, with results available in roughly 15 to 20 minutes.

A drug that grew in the national supply

According to the health department, cychlorphine was first detected in the illicit U.S. drug supply in 2024 and has since been identified in 19 states. It has appeared in powders, counterfeit prescription pills, rocks or crystals and liquids. The U.S. Drug Enforcement Administration classified cychlorphine as a Schedule I controlled substance in August, making it illegal to possess or sell; the drug has never been approved by the Food and Drug Administration for medical use.

The compound is one of a series of synthetic opioids that public health agencies have reported appearing in the U.S. supply in recent years. Louisiana's health department warned this month that at least two overdose deaths in that state involved the drug, and San Francisco identified its first cychlorphine death earlier this year.

Los Angeles County officials said the drug has been more prevalent elsewhere in the country but that they are monitoring the local supply for signs of wider circulation. The county directs residents seeking substance use disorder treatment to its SUDHelpLA.org and RecoverLA.org directories or to its Substance Abuse Service Helpline at 800-854-7771.

Why test strips miss it

The county's warning highlights a gap in standard harm reduction tools. Fentanyl test strips, a common component of overdose prevention kits distributed by health departments and community groups, are calibrated to detect fentanyl and certain analogs — not cychlorphine. Federal guidance issued this year barred the use of federal funds to purchase substance test kits, though not naloxone, leaving states and counties to replace that spending from their own budgets or settlement dollars.

The county's free testing program and its guidance to call 911 and administer naloxone are the practical responses available to residents who may encounter the drug, since a take-home strip will not flag it. The alert did not say whether additional suspected cychlorphine cases are under investigation in Los Angeles County.