What are nitazenes?

Nitazenes are strong synthetic opioids (see also New Psychoactive Substances). Common nitazenes include isotonitazene, metonitazene, etonitazene, protonitazene. Nitazenes have no medical use.

Methods of use

Nitazenes can be injected, inhaled, smoked, or swallowed as tablets.


In the UK evidence suggests that isotonitazene may be an adulterant in heroin or cocaine preparations. In October 2021, the National Crime Agency as part of ‘Operation ROPERY’ reviewed results of forensic analysis of seized drugs or associated paraphernalia. Over a quarter of cocaine samples and more than half of heroin/diamorphine samples were found to contain isotonitazene as an adulterant. Metonitazene and N-pyrrolidino etonitazene has also been detected in illicit tablets in the UK (ACMD advice on 2-benzyl benzimidazole and piperidine benzimidazolone opioids). In Scotland, nitazenes have been detected in counterfeit tablets sold as oxycodone. They have also been detected in Ireland.

It is thought that the increase in prevalence of these synthetic opioids may be a result of the successful Taliban clamp-down on heroin production in Afghanistan.


The effects of nitazenes are like other opiates, usually giving feelings of warmth, relaxation and detachment with a lessening of anxiety but also dizziness, nausea and vomiting.

The potency of nitazenes leads to a high risk of overdose. The Advisory Council on the Misuse of Drugs’ (ACMD) 2022 report: A review of the evidence on the use and harms of 2-benzyl benzimidazole (‘nitazene’) and piperidine benzimidazolone (‘brorphine-like’) opioids found that isotonitazene, was detected in 24 fatalities and Npyrrolidino etonitazene detected in 3 in the UK during 2021. 

Nitazenes have been detected in heroin and benzodiazepines supplied in Scotland and may be present in other drugs including cocaine. The Scottish Drugs Forum has worked with service providers and other stakeholders to develop information resources for people at risk of overdose due to the introduction of synthetic opioids, including nitazenes into the drug supply.

In November 2023 Ireland saw an unusually high pattern of opioid overdoses which was found to be following the emergence of nitazenes on the Irish heroin market. They rapidly responded to protect people, with an urgent analytical review of samples, mobilisation of frontline services to deliver harm reduction measures and ‘Red Alert’ risk communications issued for the affected regions (The emergence of nitazenes on the Irish heroin market and national preparation for possible future outbreaks). 

Naloxone is a medicine which can temporarily reverse the effects of an overdose caused by opiates and opioids such as Nitazenes. An overdose involving Nitazenes may require a larger amount of Naloxone to counteract it. Call 999 to ensure emergency services are on their way and then give naloxone doses one after the other, allowing 2-3 minutes between each dose.  

The law

Most synthetic opioids are Class A, meaning possession is illegal and anyone supplying them could face life in prison, an unlimited fine or both. In November 2023 the government announced that 15 new synthetic opioids would become Class A drugs in the UK.

Updated May 2024