Even a single pill can contain a lethal dose
Em abril de 2026, San Francisco registrou sua primeira morte confirmada por overdose ligada ao ISO, um opioide sintético da família das nitazenas capaz de ser até vinte vezes mais potente que o fentanil. A substância circula invisível aos testes rápidos convencionais, deixando usuários sem qualquer consciência do que consomem. Num ciclo que já dura décadas, a crise dos opioides não recua — ela se reinventa, tornando-se a cada geração mais letal e mais difícil de combater.
- Uma única pílula de ISO pode conter dose letal, e a morte de abril em San Francisco revelou que a substância já circula misturada a outros opioides sem que usuários saibam o que estão ingerindo.
- Os testes rápidos padrão, pedra angular da redução de danos nas ruas americanas, são cegos ao ISO — tornando invisível exatamente aquilo que mais mata.
- Socorristas enfrentam uma armadilha dupla: a naloxona, antídoto clássico para overdose de opioides, pode não funcionar de forma previsível contra as nitazenas, deixando equipes de emergência sem resposta garantida.
- A DEA catalogou mais de novecentos casos desde 2019 e alerta que o ISO está sendo misturado ao fentanil ou vendido de forma enganosa, expandindo silenciosamente seu alcance para além de San Francisco.
- Imagens do bairro Tenderloin mostram pessoas imóveis nas calçadas em plena luz do dia — o rosto visível de uma crise que, segundo pesquisadores, não está se estabilizando, mas evoluindo.
Em abril deste ano, San Francisco registrou sua primeira morte confirmada por overdose ligada ao ISO — nome de rua do isotonitazeno, um opioide sintético da família das nitazenas estimado em até vinte vezes mais potente que o fentanil. A vítima havia consumido a substância misturada ao ciclorfan, outro opioide sintético. O episódio levou o Departamento de Saúde da cidade a emitir alerta público sobre uma droga que escapa dos testes rápidos convencionais, deixando usuários sem qualquer noção do que estão ingerindo.
O ISO pode ser fumado, injetado ou ingerido em comprimidos, adaptando-se a diferentes formas de uso. Sua periculosidade vai além da potência: a invisibilidade nos testes de triagem e o comportamento imprevisível diante da naloxona — o antídoto padrão para overdoses por opioides — complicam gravemente a resposta médica de emergência. Mesmo quando o socorro chega a tempo, a intervenção que salva vidas pode simplesmente não funcionar.
Imagens do bairro Tenderloin mostram pessoas prostradas nas calçadas por longos períodos, dobradas ou estendidas nas ruas em plena luz do dia. O pesquisador Christopher Rufo, do Manhattan Institute, documentou as cenas e relatou conversas com traficantes locais confirmando que o ISO ganha espaço nos mercados de rua. Para ele, o fenômeno é parte de uma corrida armamentista de uma década: de heroína ao fentanil, e agora ao ISO.
A DEA monitora a substância desde 2019 e já catalogou mais de novecentos casos, com pico de trezentos e cinquenta e oito ocorrências em 2021. A agência alerta que as nitazenas estão sendo misturadas ao fentanil ou vendidas sem que os compradores saibam o que adquirem. Em Los Angeles, o ISO ainda não é problema significativo, mas autoridades relatam aumento de misturas clandestinas envolvendo fentanil, outros sintéticos e até tranquilizantes veterinários. Em San Francisco, o fentanil ainda responde por mais da metade das mortes por drogas — mas o surgimento do ISO sinaliza que a crise não está se estabilizando. Ela está evoluindo, tornando-se a cada passo mais difícil de ver e de tratar.
In April of this year, San Francisco recorded its first confirmed overdose death linked to a synthetic opioid called ISO—a substance so potent that a single pill can contain a lethal dose. The victim had consumed isotonitazeno, the drug's technical name, mixed with another synthetic opioid called cyclorfan. The death prompted the city's Department of Health to issue a public warning about a drug that circulates largely undetected by standard testing kits, meaning users often have no idea what they're actually taking.
ISO belongs to a family of synthetic opioids known as nitazenes, compounds that federal agencies have been monitoring with growing concern. Researchers at the Center for Forensic Science Research and Education estimate the substance can be up to twenty times more potent than fentanil—itself a drug that has driven much of the overdose crisis across American cities. The drug can be smoked, injected, or swallowed as a pill, making it adaptable to different routes of use. What makes it particularly dangerous is not just its strength but its invisibility: the rapid tests that have become standard in harm reduction and emergency medicine cannot identify its presence.
Video footage from San Francisco's Tenderloin neighborhood, a district marked by visible drug use and homelessness, shows the drug's immediate effects. In the recordings, people lie motionless on sidewalks for extended periods, bent over or sprawled across public streets in broad daylight. The images were documented by researcher Christopher Rufo of the Manhattan Institute and circulated by the New York Post. Rufo reported conversations with local drug dealers indicating that ISO is gaining ground in the city's street markets. He framed the trend as part of a decade-long escalation: "Over the last ten years, there's been an arms race to increase the potency of opioids—from heroin to fentanil and now to ISO."
The Drug Enforcement Administration has also sounded an alarm. The agency notes that nitazene-family drugs are being mixed into fentanil supplies or sold to users without their knowledge of what they're purchasing. A second complication troubles medical responders: overdoses involving these substances do not always respond predictably to naloxone, the medication designed to reverse opioid poisoning. This means that even when emergency services arrive quickly, the standard life-saving intervention may not work as expected.
The DEA first encountered isotonitazeno in drug seizures in 2019. Since then, the agency has cataloged more than nine hundred cases involving the substance. The highest concentration appeared in 2021, with three hundred fifty-eight recorded incidents. In Los Angeles, authorities say ISO has not yet become a significant problem, though investigators there report a rising tide of clandestine drug mixtures combining fentanil with other synthetic compounds and even veterinary tranquilizers. Across San Francisco, fentanil remains the dominant driver of overdose deaths, linked to just over half of all drug and alcohol fatalities in the city. But the emergence of ISO suggests the crisis is not stabilizing—it is evolving, becoming harder to detect and harder to treat.
Notable Quotes
Over the last ten years, there's been an arms race to increase the potency of opioids—from heroin to fentanil and now to ISO— Christopher Rufo, Manhattan Institute researcher
Even a single pill can contain a lethal dose— San Francisco Department of Health
The Hearth Conversation Another angle on the story
Why does ISO matter more than the other synthetic opioids already circulating?
Because it's invisible to the tools people use to stay safe. You can test for fentanil. You can't test for this. Someone thinks they're using one thing and they're using something twenty times stronger.
And the naloxone issue—that's a separate problem from potency?
Yes. Even if someone gets to a hospital or a paramedic finds them, the standard reversal medication might not work. It's like the drug was designed to defeat every safety net we built.
The videos from Tenderloin—are those people dead or just incapacitated?
Just incapacitated. But the line between those two states is thinner with ISO than it's ever been. One pill. That's all it takes.
How does it get into the supply if dealers are mixing it deliberately?
Some of it is deliberate—dealers want potency because it's cheaper to produce and more addictive. But a lot of it is accidental contamination. Someone buys powder they think is fentanil and it's actually ISO, or it's both, and they have no way to know until someone overdoses.
Is there any sense of how many people are using it versus how many are dying?
That's the terrifying part. We only know about the deaths. The nine hundred cases the DEA cataloged—those are seizures, not users. The real number of people exposed is probably much larger and completely invisible.