Nitazenes, a class of synthetic opioids, are increasingly found everywhere. While (still) relatively obscure, detections of these opioids have been reported in Europe, Canada, Australia, Brazil, and the United States as early as 2019. Nitazenes have now been found on every continent according to the UN Office on Drugs and Crime (UNODC). However, the absence of routine testing for nitazenes, as well as lacking drug checking infrastructure worldwide, could suggest that nitazenes are much more prevalent across the globe than currently known.
What are nitazenes?
Nitazenes are a class of synthetic opioids in the benzimidazole class that contains more than 20 unique compounds including isotonitazene, protonitazene, metonitazene and etonitazene. While these substances seem to have emerged out of nowhere, nitazene analogues were first synthesised in the late 1950s by CIBA Pharmaceuticals (now Novartis) as a promising new non-addictive opioid analgesics. However, they were never approved for clinical use due to their potency and associated risk of overdose and respiratory failure. Its comparable potency varies across different analogues, ranging from 10 (like isotonitazene and metonitazene) to 20 (etonitazene) times stronger than fentanyl. Effects of nitazenes can last 4 or more hours and, like fentanyl, can cause chest wall rigidity that is known as “wooden chest syndrome” that often requires manual ventilation.
In recent years, nitazenes have been increasingly found to be used as alternatives to common opioids such as fentanyl and heroin, as well as adulterating other illicit drug markets such as cocaine, benzodiazepines, or counterfeit prescription pharmaceuticals such as oxycodone. Commonly sold as a powder, it has also been found (in small quantities) in liquid vapes thought to contain synthetic cannabinoids, both in the UK and Australia.
Nitazenes’ harms primarily stem from people not knowing that they are consuming nitazenes, whether they appear as unexpectedly stronger batches of opioids, or within other drug supplies – which is particularly dangerous, as people may not be expecting to overdose or have naloxone on hand.
Where are nitazenes coming from?
While the production and trafficking of nitazenes is still unclear, there are some indications that most of it originates in China and is then shipped worldwide. The US indicted several Chinese chemical manufacturing companies for exporting nitazenes, fentanyl and other opioid precursors into the country last year. A British investigation highlighted that nitazenes were openly sold on websites like Soundcloud and X and also originated from China. In another instance however, Australian border forces seized 198 grams of nitazenes going from the UK to Australia through regular mail, meaning either production occurred or went through there.
Drug seizures and indictments are currently the only glimpses we have into the global nitazene trade. These pieces of information, coupled with their detection across national drug checking systems, underscore the possibility of nitazenes being produced and distributed worldwide, as well as across multiple drug supplies.
“Kush” and nitazenes across West Africa
Across Africa, there have been few detections of nitazenes, most likely due to a lack of drug checking infrastructure from the government and civil society organisations. With ports across West Africa increasingly playing a key role as transiting hubs for global drug trafficking routes, there is a risk that nitazenes are passing through these nations undetected. Confirming their presence in local drug markets would help better understand whether they are being trafficked across the same routes as other substances, and help nations prepare to reduce harms from their use.
In West Africa, drug concerns have been focused on the growing use of many new psychoactive substances. One of them, “kush”, a drug of unclear contents, has garnered much global attention as the President of Sierra Leone declared a national emergency on drugs in April 2024 due to its prevalence and widespread consumption, particularly by young people.
Governments and media have speculated that “kush” is a cocktail of fentanyl, PCP, tramadol, and other sensational claims like human bones, with little evidence given to validate these findings. The reality seems to be that most “kush” is composed of local or imported leaves sprayed with synthetic cannabis, as well as nitazenes, which contribute to a number of adverse effects.
As the drug checking expert assigned to conduct research with the Global Institute of Transnational Organised Crime (GI-TOC) in Sierra Leone and Guinea-Bissau, we analysed 96 drug samples were analysed, of which 46 were of ‘kush’. Nitazenes were detected in 83% of the ‘kush’ samples in Sierra Leone and 56% of the samples in Guinea-Bissau. In total, 77% of all ‘kush’ samples tested positive for nitazenes.
Without the preliminary research done in Guinea-Bissau and Sierra Leone, it would have been a challenge to detect nitazenes in the kush supply. While secondary testing is still pending (based on spectrometer results alongside immunoassay nitazenes strip testing) it appears that nitazenes are a prevalent psychoactive ingredient in the existing kush supply. However, with limited access to adequate testing for novel psychoactive substances (NPS), West African authorities are expected to take important steps to control drug harms practically in the dark.
More reliable nitazene testing is needed
As nitazene detections increase in opiates as well as other drug markets, the need for drug checking becomes increasingly more urgent. Data confirming nitazenes’ presence in drug markets are coming from countries with substantial substance analysis programmes, such as Canada, the UK, Australia, and New Zealand. There’s a high likelihood that if other countries had similar testing capacity and resources for drug checking services, there would be more information on where nitazenes are appearing, as well as who is consuming them.
There is also a chance that nitazene detection has been limited due to testing-specific issues. Nitazenes are not routinely tested for in post-mortem toxicology tests, meaning they are often not linked to overdoses or as the cause of other adverse health effects. This is understandable, as nitazenes are relatively uncommon. The UK for example had a similar issue with no detections of xylazine in the drug supply before it was more widely known that xylazine was more common than thought. Toxicology services may not know they should be looking for nitazenes in the first place.
As a result, nitazenes may not be properly detected in overdoses, especially in scenarios where fentanyl was ruled out, and there is a lack of interest, awareness, means, or a combination of these factors, to find out the real culprit.
Front-line harm reductionists in the US have told me they have felt suspicious of mysterious overdoses and other opioid-like respiratory symptoms that are being attributed to fentanyl even when none have been detected. Given naloxone is effective with fentanyl or nitazenes, there may be a lack of time or resources to verify which opioids are actually causing overdoses in the first place.
At the consumer level, there is still much to improve on how to detect for nitazenes. Speaking with test-strip experts and laboratories, there are concerns around existing immunoassay test strips for nitazenes and the quality of their results. This is due to the cross-reactivity of the test-strips with both caffeine and heroin, meaning that they will flag positive for the presence of nitazenes, even when there aren’t any in the sample. Our current technology to detect nitazenes is still catching up, and is not currently as effective as it would ideally be.
More knowledge needed to prevent more harms
What we are witnessing now is what happens when novel substances float around undetected, in a complex context of addiction, drug mixtures, and spiralling drug-related deaths. There is little understanding on why people are overdosing, with minimal capacity to detect new substances in the market. This is the reality of drug markets everywhere – from Sierra Leone to the United States.
It’s unlikely that nitazenes will be disappearing any time soon: with law enforcement cracking down on fentanyl, new substances – like nitazenes – will become more appealing for drug traffickers, especially if no-one is looking for them. With limited partnerships and knowledge exchange between local, national, and global authorities, or a centralised global database to track new psychoactive substances, the lack of collaboration means international trends won’t be uncovered until it’s too late.
Nonetheless, the detection of nitazenes in the “kush” supply in Sierra Leone and Guinea-Bissau has been a sobering moment that highlights the global dissemination of these substances. More awareness and cooperation is needed to create an accurate picture of the drug market, and to develop responses to prevent more suffering and death.
