Nitazenes are a class of synthetic opioids derived from the chemical structure 2-benzyl-benzimidazole. They were first synthesised in the 1950s as potential painkillers by researchers at Chemische Industrie Basel, a Swiss company, but were never approved for medical or veterinary use because of their extremely narrow therapeutic window—the dosage range that relieves pain without unacceptable side-effects. Scientists estimate that nitazenes can be hundreds of times stronger than heroin, with some thought to be dozens of times stronger than fentanyl.
Nitazenes first appeared on the illicit drug market in 2019. Since then, clusters of overdoses have been reported across Africa, the Americas, Australia and, in particular, Europe. They are often sold disguised as other products: in Ireland they have appeared as "Chinese heroin"; in Australia they have been found masquerading as MDMA. In West Africa they have turned up as contaminants in cannabinoid products.
Synthetic opioids suit illicit drugmakers. They are easier to produce than heroin, which depends on growing opium poppies. Because their chemical structures can easily be tweaked, producers can circumvent bans on specific compounds. Because they are so potent, smugglers can pack more lucrative highs into smaller, lighter packages.
Several developments created the conditions for nitazenes to flourish. America stepped up its efforts against fentanyl in 2018 and banned all fentanyl analogues. China, the main producer of fentanyl, followed suit in 2019 and local production plunged. In 2021 the Taliban seized power in Afghanistan and banned opium production, possibly disrupting Europe's heroin supply. Fentanyl itself has been controlled under a UN convention since 1964.
Nitazenes exemplify the Iron Law of Prohibition, proposed by Richard Cowan, a drug-legalisation activist, in 1986. The principle holds that banning one compound opens the door to a new, stronger alternative—just as Prohibition in America led to a shift from beer to spirits, which are easier to smuggle and more dangerous. America's opioid crisis can also be understood this way: a clampdown on prescriptions of opioid painkillers left masses of patients unable to get their fix legally, so many turned to illicit dealers and got hooked on stronger drugs such as fentanyl.
Research by Marthe Vandeputte, a toxicologist at the University of Ghent, published in ACS Chemical Neuroscience in 2021, showed that isotonitazene breaks down inside the body into another, yet more potent, nitazene. As the original drug disappears, a stronger one—albeit in a lower concentration—takes over, potentially prolonging the effects. This appears to set at least some nitazenes apart from heroin and fentanyl and has implications for emergency treatment: standard doses of naloxone, the usual antidote, may not be sufficient.
Britain's National Crime Agency believes at least 333 deaths in Britain in 2024 were linked to nitazenes.
Naloxone, an antidote to opioid overdoses, can reverse the effects of nitazenes if administered in time, though higher doses may be needed than for heroin overdoses. In January 2025 the British government used a generic definition—compounds derived from the core structure of 2-benzyl-benzimidazole—to categorise all nitazenes as class A drugs, the most severe criminal classification, in the hope of capturing future variations. China implemented a nitazene ban using a similar generic definition in June 2025. Overdose patients and street drugs should be tested to reveal how and where nitazenes are being taken. Rich countries should share information about new nitazene structures with poor ones.
When I was younger, I could remember anything, whether it had happened or not; but my faculties are decaying now and soon I shall be so I cannot remember any but the things that never happened. It is sad to go to pieces like this but we all have to do it.