ISO Explained

Apocalyptic New Designer Drug

Isotonitazene, better known as ISO, is taking a massive swing in the synthetic drug business. ISO is one of the newest designer drugs to hit the market with a deadly impact. Isotonitazene was first synthesized and patented in 1959 as part of research carried out by the Swiss pharmaceutical company CIBA. These studies showed that Isotonitazene was around 500 times more potent than morphine. While three closely related drugs (etonitazene, clonitazene, and metonitazene) were studied in humans, Isotoniazene was not studied on humans or animals by CIBA. Later studies have shown that isotonitazene behaves similarly to other opiates by activating opioid receptors, which then regulate the response to pain and produces feelings such as euphoria. While further studies are ongoing, clinical toxicological data from post-mortem human specimens highlight the potential lethality of this drug with an average blood concentration of only 2.2 ng/mL. This is consistent with the stronger effect that this compound has relative to another more common and lethal drug, fentanyl. ISO is 20 to 100 times stronger than fentanyl, raising concerns about the popularity of ISO moving forward. This makes ISO deadly even to the touch. It is advised not to come into contact with ISO as there is the possibility of overdosing from just touching the substance.

According to reports, ISO is approximately 20 to 100 times stronger than fentanyl, which is 50 to 100 times more potent than morphine.

Isotonitazene started making its way around the world in 2019, from Alberta in March and then on to Belgium in August. Like many other illicit drugs, ISO is manufactured in China at chemical plants. The drug is then combined and pressed into counterfeit pills. After production, the drug is shipped to Mexico to be sold to cartels, who will traffic ISO into the U.S to be then sold on the streets. Since ISO is so potent, it is more profitable to produce and more compact to smuggle than other opioids. This makes it appealing to drug dealers. In April 2019, the United States Customs and Border Protection seized Isotonitazene in California. This is the first report of the U.S government seizing ISO.

The terrible truth is that ISO is extremely deadly, but unfortunately, many people who buy counterfeit pills don’t even know ISO is laced in or replaced. There are countless stories of family members losing loved ones who believed they were buying hydrocodone and overdosing on ISO or Fentanyl. As of now, there is no easy way to test specifically for ISO outside of an LC-MS-MS, but researchers are hopeful there will be a more rapid option soon.


Isotonitazene Quantitation and Metabolite Discovery in Authentic Forensic Casework,
Alex J. Krotulski, Donna M. Papsun, Sherri L. Kacinko and Barry K. Logan: Journal of Analytical Toxicology, 2022,

The Rise and Fall of Isotonitazene and Brorphine: Two Recent Stars in the Synthetic Opioid Firmament, Marthe M. Vandeputte, Alex J. Krotulski, Donna M. Papsun, Barry K. Logan and Christophe P. Stove: Journal of Analytical Toxicology, 2022

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