The number of sales of nitazines on the dark web has increased, while the amount of fentanyl (pictured) has decreased.Photo: Gary Coronado/Los Angeles Times/Getty
Researchers studying trends in illicit drug use are concerned that sales of a powerful class of synthetic opioids called nitazenes are rising around the world.
Opioid drugs include heroin and morphine. Unlike drugs that are derived from natural 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 as loss of consciousness, coma and death.
But since 2019, there has been an increase in reports of nitazene use, according to World Drug Report 2025which was released in June. In 2023, the report said, authorities in 28 countries seized 20 different nitazenes and reported them to the United Nations Office on Drugs and Crime (UNODC) Early Warning Advisory Service on New Psychoactive Substances.
Nitazenes can be up to 500 times more potent than opium-derived drugs. For example, butonitazene is 2.5 times more potent than heroin, while isotonitazene and etonitazene are 250 and 500 times more potent than heroin, respectively.
This means that even a small amount can be fatal. In the United Kingdom, there were 179 confirmed deaths from nitazene overdose in the year to 31 May 2024. It has been reported that thousands of people may have died from nitazene overdoses in the United States since 2019. In Australia, researchers note that the unpredictable presence of nitazenes in various drugs increases the risk of overdose in the country.
According to Suzanne Nielsen, an addiction researcher at Monash University in Melbourne, Australia, most nitazine overdoses are unintentional. Overdose usually occurs when nitazenes are sold as other drugs such as heroin, oxycodone, and MDMA (also known as ecstasy). An overdose can be treated with naloxone, a drug that has long been used to treat other opioid overdoses. Greater awareness among drug users and their families could help save lives, Nielsen adds.
