San Francisco records first overdose death involving new street drug more potent than fentanyl

San Francisco health officials rang the alarm Friday about a new synthetic opioid 10 times more potent than fentanyl that surfaced for the first time in an overdose victim earlier this month, prompting renewed warnings about the dangers of counterfeit pills.

The victim is believed to have consumed the synthetic opioid N-Propionitrile chlorphine, also known as cychlorphine, while taking counterfeit pills. Fentanyl test strips - commonly used to check illicit drugs for fentanyl - will not detect N-Propionitrile chlorphine, according to officials.

San Francisco Public Health Director Daniel Tsai said the death reinforces the notion that "even a single pill has the potential to be deadly."

People are urged to administer the opioid-reversing medication naloxone in any suspected overdose, including those that may involve the newly detected opioid.

The victim's toxicology report also detected the synthetic opioid N-Desethyl isotonitazene and benzodiazepines, a class of depressant drugs often used to treat anxiety, insomnia and seizures.

Like fentanyl, N-Propionitrile chlorphine and N-Desethyl isotonitazene cause drowsiness and respiratory depression. The mixing of opioids and non-pharmaceutical benzodiazepines in the same pill or powder has grown increasingly common in recent years - and can be especially deadly.

It's unclear at this point how prevalent N-Propionitrile chlorphine has become in San Francisco's drug supply. A lab at Zuckerberg San Francisco General Hospital that tests substances and patients accessing opioid use disorder treatment has not found the opioid during its testing, said Dr. Phillip Coffin, the public health department's director of substance use research.

Although fentanyl still accounts for 3 out of every 4 overdose deaths in San Francisco, officials continue monitoring for emerging drugs that could worsen the city's drug crisis. Last year, the city recorded its first fatal overdose involving the potent animal tranquilizer medetomidine. Medetomidine is in the same family of drugs as xylazine, a non-opioid sedative commonly known as "tranq." Xylazine was first discovered in San Francisco overdose victims in late 2022, but neither it nor medetomidine has become common in San Francisco's drug supply.

San Francisco's overdose death toll remained largely unchanged in 2025 compared with the previous year. The city saw 625 overdose deaths in 2025 and 635 in 2024. From January through March of this year, San Francisco has recorded 148 fatal overdoses - down 26% during the same period last year, according to data from the Office of the Chief Medical Examiner.

"Whilst we have made progress, these numbers are still far too high," Tsai said. "We have much more work to do together."

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This story was originally published April 24, 2026 at 7:09 PM.