Sale listing on the dark web for nitazenes have gone up as listings for fentanyl (pictured) have gone down.Credit: Gary Coronado/Los Angeles Times/Getty
Researchers who study trends in illicit drug use are concerned that sales of a potent class of synthetic opioids called nitazenes are on the rise globally.
The opioid class of drugs includes heroin and morphine. Unlike those drugs, which are derived from naturally occurring opium, nitazenes are synthesized from scratch in a laboratory. The first nitazenes were developed as painkillers in the 1950s, but were never approved for medical use because they carried a high risk of dangerous side effects such loss of consciousness, coma and death.
But since 2019, there has been a rise in the reported use of nitazenes, according to the World Drug Report 2025, which was released in June. In 2023, the report states, 20 different nitazenes were seized by authorities across 28 countries and reported to the United Nations Office on Drugs and Crime (UNODC) Early Warning Advisory on New Psychoactive Substances.
Nitazenes can be as much as 500 times more potent than opium-derived drugs. For example, butonitazene is 2.5 times more potent than heroin, whereas isotonitazene and etonitazene are 250 and 500 times more potent, respectively.
This means that just a tiny amount can be deadly. In the United Kingdom, there were 179 confirmed deaths from nitazene overdoses in the year to 31 May 2024. And reports suggest that thousands of people might have died from nitazene overdoses in the United States since 2019. In Australia, researchers note that the unpredictable presence of nitazenes in various drugs is increasing the risk of overdose in the country.
Most nitazene overdoses are unintentional, says Suzanne Nielsen, an addiction researcher at Monash University in Melbourne, Australia. Overdose tends to occur when nitazenes are sold as other drugs, such as heroin, oxycodone and MDMA (also known as ecstasy). Overdoses can be treated with naloxone, a drug that has long been used to treat other opioid overdoses. More awareness of this among drug users and their families could help save lives, Nielsen adds.
