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Deadly new drug ripping through SF is Narcan-resistant, users say

Some locals believe that a drug called isotonitazene, which is reportedly stronger than fentanyl, has made its way to San Francisco. | David Sjostedt/The Standard

People who use opioids in San Francisco are reporting a powerful new drug that is stronger than fentanyl has made its way to the city.

The Standard spoke to six people using drugs in the Tenderloin and SoMa neighborhoods on Tuesday who claimed they had used an opioid called isotanitazene, or “ISO,” which is believed to be more powerful than fentanyl

The Drug Enforcement Administration has confirmed the drug’s presence in cities on the East Coast, and locals are concerned that it could eventually exhaust San Francisco’s supply of overdose reversal medication because ISO requires a faster response and a higher dose of antidote to be effective. 

A man named Joey, who was smoking fentanyl in a SoMa alleyway, told The Standard that he overdosed on ISO last week and was only resuscitated after three hits of the opioid antidote Narcan and a shot of adrenaline.

“I woke up, and there was a group of people around me saying, ‘Oh my, god you were gone,’” Joey said. 

The Department of Public Health and the local Drug Enforcement Agency say they haven’t found ISO in the city’s drug supply, but drug users who spoke to The Standard said that they can taste a difference from their usual cuts of fentanyl. Several recounted the drug’s bitter taste and unusually nauseating effects, saying they purchased the powder for two to three times the price of fentanyl. 

ISO is marketed as a step above the cleanest cuts of fentanyl, which are sold between $10 and $20 per gram, according to those who spoke to The Standard. Drugs sold as ISO can fetch upwards of $30 per gram, they said. 

A man name Frank displays yellow rocks of fentanyl that he was sold in San Francisco. | David Sjostedt/The Standard | Source: David Sjostedt/The Standard

“A lot of us try to stay away from it. We don’t like the taste,” Joey said. “But there are days when you need it.”

Emergency responders have reversed over 3,000 overdoses since December 2021 as city legislators waver between harm reduction and criminal justice measures to stem fentanyl deaths. The health department plans to create facilities for supervised drug use, but the opening of the first site is on hold while city officials hash out the details of how such sites can be legally funded and operated. 

According to preliminary data, 620 people died of fatal overdoses in San Francisco last year while the health department has failed to make sufficient on-demand treatment available to people who use drugs.

Supervisor Matt Dorsey, who represents the SoMa neighborhood, said that the introduction of powerful new drugs to the city’s street supply could exacerbate a crisis that has already taken more lives than Covid in San Francisco. 

Supervisor Dorsey presents a photo of the amount of fentanyl that triggers an overdose during a press conference in San Francisco on Aug. 10, 2022. | Camille Cohen/The Standard

Dorsey submitted a letter of inquiry to the Chief Medical Examiner’s Office on Tuesday asking how the city can better fund data collection of drug deaths to be proactive in its response.

“What we could be looking at is a public health calamity that is worse than the AIDS crisis,” Dorsey said. “We need to be ready for this.” 

John Ostwalt, who said he had been sleeping on the streets of San Francisco for 20 years, said that he passed out while walking down the street after smoking ISO on Monday, suffering a black eye from falling into a car window. Ostwalt said the drug is spreading on San Francisco’s streets, but that it isn’t as popular as fentanyl because it’s more expensive.

John Ostwalt, who said he had been sleeping on the streets of San Francisco for 20 years, said that he passed out while walking down the street after smoking a powerful new opioid called ISO on Monday, suffering a black eye from falling into a car window. | David Sjostedt/The Standard

Ostwalt said five of his friends overdosed on the drug in a single day last week. He criticized the city for closing a safe consumption site called the Tenderloin Center, which reversed over 300 overdoses during its tenure. 

“People are looking for it because we’re looking for the strongest stuff possible,” Ostwalt said. “When a person overdoses and dies, that’s what I want to get.” 

Still, there are others who chalked up any ISO wave to a combination of rumors and savvy marketing by drug dealers. 

“Honestly, it’s probably just a different cut of fentanyl,” said a man named Frank, who was in possession of a white powder that was sold to him as ISO. “I think it’s just a rumor.” 

David Sjostedt can be reached at