‘There has never been a more dangerous time to take drugs’: The rising threat of synthetic opioids

New synthetic opioids (NSOs) are one of the fastest-growing groups of new psychoactive substances around the world. In the early hours of September 14 2021, three men parked in a quiet car park in the southern English market town of Abingdon-on-Thames. The men, returning from a night out, had pulled over to smoke heroin. Unknown to them, the drug had been fortified with a nitazene compound called isotonitazene, a highly potent new synthetic opioid. Two of the men, Peter Haslam and Adrian Davies, overdosed and went into cardiac arrest. The third, Michael Parsons, tried to save them and himself by injecting naloxone, an opioid overdose antidote. Despite paramedics also trying to resuscitate Haslam and Davies, both died at the scene.

Their deaths were among at least 27 fatalities linked to nitazenes that year in the UK. Since then, nitazenes – otherwise known as 2-benzylbenzimidazole opioids – have become more prevalent in the UK’s illegal drug supply, leading some experts to warn that they are a major new threat because of their extreme potency. In June 2023, the UK’s most recent outbreak of deaths linked to synthetic opioids emerged in the West Midlands when drug dealers used nitazenes to fortify low-purity heroin. By August, there were 21 nitazene-related fatalities in Birmingham alone. In some cases, dealers also added xylazine (colloquially known as “tranq”), a non-opioid sedative used by vets.

The increasing availability of these and other synthetic drugs led the UK’s National Crime Agency (NCA) to warn in August 2024 that “there has never been a more dangerous time to take drugs”. Like Haslam and Davies, many heroin users are unaware they might also be consuming nitazenes, which significantly increase the risk of overdose. Given their potency, only a small amount of nitazene is required to produce a fatal dose. While some studies have concluded that nitazenes are even more potent than the synthetic opioid fentanyl, which causes many thousands of deaths in the US, the NCA judges it a “realistic possibility” that the potency of both substances are “broadly equivalent” – making them roughly 50 times more potent than heroin.

Illicit drug use is damaging large parts of the world socially, politically and environmentally. Patterns of supply and demand are changing rapidly. In our new longform series Addicted, leading drug experts bring you the latest insights on drug use and production as we ask: is it time to declare a planetary emergency?. Officially, more than 400 deaths plus many non-fatal overdoses were linked to nitazenes in the UK between June 2023 and January 2025. But this is likely to be an underestimate because of gaps within forensic and toxicology reporting. These figures come amid record levels of drug-related deaths in England and Wales. In 2023, there were 5,448 deaths related to drug poisoning, an 11% increase on the previous year and the highest total since records began in 1993.

This is of particular concern given that the UK has the largest heroin market in Europe, comprising around 300,000 users in England alone. While nitazene-related deaths are still relatively low (although by no means insignificant) compared with those from heroin and other opioids, these new synthetic opioids are cheap and easy to buy, and offer dealers multiple advantages over traditional plant-based drugs.

Unlike opium, nitazenes and other synthetic opioids can be produced anywhere in the world using precursor chemicals that are often uncontrolled and widely available. Producer countries including China and India have not yet banned all nitazene compounds, meaning they are sold legally – mostly online. Chemical manufacturing companies in these countries can synthesise nitazenes at scale using a comparatively easy three or four-step process.

Opioid use death rates around the world:. For the past 15 years, I have researched and advised on the international narcotics industry, especially the Afghan drug trade, as an academic, UK Home Office official and consultant. I’ve observed many shifts within global drug markets, and I believe the increasing availability of synthetic drugs in the UK and Europe may represent a new chapter in illicit drug use here – with the emergence of nitazenes only adding to these concerns.

New synthetic opioids (NSOs) are one of the fastest-growing groups of new psychoactive substances around the world. The EU Drugs Agency (EUDA) currently monitors 81 NSOs – the fourth-largest group of drugs under observation. NSOs largely fall into two broad groups: fentanyl and its analogues, and non-fentanyl-structured compounds – these include nitazenes, among many other substances. Many of these “new” synthetic opioids have, in fact, existed for decades. Nitazenes were first synthesised in the 1950s by the Swiss pharmaceutical company, Ciba Aktiengesellschaft, as pain-relieving analgesics, although they were never approved for medical use.

Prior to 2019, there had only been limited reports of nitazenes in the illegal drug supply – including a “brownish looking powder” found in Italy in 1966; the discovery of a lab in Germany in 1987; several nitazene-related deaths in Moscow in 1998; and a US chemist illegally producing the drug for personal use in 2003. But since nitazenes re-emerged at the end of the last decade, over 20 variants have been discovered.