Fatal Overdose Involving Novel Synthetic Opioids

The San Francisco Department of Public Health (SFDPH) is warning the public about powerful non-fentanyl synthetic opioids that have been detected in a recent fatal overdose. See the health alert sent to providers on April 23, 2026: Health Alert: Fatal Overdose Involving Novel Synthetic Opioids | SF.gov

N-Propionitrile Chlorphine (also known as cychlorphine) and N-Desethyl Isotonitazene are two non-fentanyl, synthetic opioids that have been detected in overdose decedents across the United States, including a person who died of overdose in San Francisco in April 2026. The tragedy marks the first time cychlorphine -- estimated to be 10 times more powerful than fentanyl and undetectable by fentanyl test strips -- has been detected in San Francisco.  

In the San Francisco case, the decedent is believed to have ingested counterfeit pills containing these synthetic opioids, as well as ethyl bromazolam, a benzodiazepine that is not approved by the FDA. Fentanyl was not detected in the toxicology screening completed by the San Francisco Office of the Chief Medical Examiner.  

Counterfeit pills can look like prescription medications from a licensed pharmacy but contain unknown and potentially lethal substances, putting people at risk for overdose. There is no way to tell from appearance alone whether a pill is safe. Even a fraction of a counterfeit pill can kill someone. The safest choice is to avoid any pill that was not prescribed to you by a pharmacy, even if it was given to you by a friend or family member.  

Like with fentanyl and other opioids, an overdose from other synthetic opioids can be reversed by naloxone, a safe over-the-counter medication also known by the brand name Narcan. 911 should be called, even if the person appears to respond to naloxone. To learn how to use naloxone and save a life from overdose, visit About Naloxone | SF.gov

Substance use disorder treatment is effective and reduces the risk of overdose. The two most effective medications to treat opioid addiction, buprenorphine and methadone, are widely available through SFDPH. To access treatment today, call SFDPH at 888-246-3333.