A Dangerous New Class of Synthetic Opioid Is Spreading

Some nitazenes are far more potent than fentanyl.

- 

On a morning in November 2023, Dr Eamon Keenan, a psychiatrist who runs addiction services at Ireland's state-funded healthcare provider, received a worrying phone call. "People in homeless accommodation and hospitals are collapsing," he recalls being told. It was the start of a bleak few weeks.

In Dublin and Cork, the country's biggest cities, 77 people would end up overdosing. The initial suspect was dodgy heroin, but laboratory analysis revealed a dangerous new class of drugs—nitazenes. Since then, these have been detected everywhere, from Freetown in Sierra Leone to Sydney in Australia.

Nitazenes are opioids, a family of chemicals that includes morphine and heroin, as well as the much stronger fentanyl, which causes tens of thousands of deaths in the US every year. Although measures of their potency vary, scientists estimate that nitazenes can be hundreds of times stronger than heroin, with some thought to be dozens of times stronger than fentanyl.

But whereas heroin and fentanyl have long histories as medical analgesics and have therefore been extensively studied, hardly any research exists on nitazenes. With nitazene use rising around the world, and in particular, in Australia and Europe, scientists are scrambling to gather data on how dangerous these new drugs are and who is at risk. The emerging picture is grim.

Like fentanyl, nitazenes are molecules that do not occur in nature and must be fully synthesized from precursor chemicals in laboratories. All derive from a chemical structure called 2-benzyl-benzimidazole, a small set of connected rings made up of atoms of carbon, hydrogen and nitrogen. The first nitazenes were made in the 1950s as potential painkillers by researchers at Chemische Industrie Basel, an erstwhile Swiss company, but problems with these chemicals soon became apparent.