University of Dundee experts have warned that testing strips routinely distributed by harm reduction services across the UK to prevent drug overdoses may not be fit for purpose, putting the lives of people who use drugs at risk.
Researchers from the University’s Leverhulme Research Centre for Forensic Services (LRCFS) have shown that the strips do not detect many of the potent synthetic opioids, known as nitazenes, that they are designed to identify.
The ability to detect nitazene compounds in the UK has raised concerns among healthcare professionals, public health authorities, and law enforcement due to the increased variety of these compounds in circulation and the risk of fatal overdose. In response, thousands of nitazene testing strips have been distributed to help people check for these substances in drugs they may consume.
The LRCFS team found that false positives were observed when testing seized heroin samples, caused by the presence of caffeine, which is one of the most common cutting agents detected in illicit drug samples. False negatives were also obtained for some nitazene compounds now in circulation in the UK, such as metodesnitazene, which has been detected in drug related deaths.
Lead researcher Dr Victoria Marland said caution should be exercised when deploying these nitazene test strips as frontline tests in both criminal justice and public health contexts.
“While the strips successfully detected a majority of nitazene compounds, their inability to identify certain analogs raised serious concerns,” she said. “A negative result may give people false reassurance, even though dangerous synthetic opioids could still be present.
“Additionally, the occurrence of false positives, due to the presence of caffeine – a common adulterant in illicit substances – raises concerns about their suitability for use as a harm reduction method.
“The strips typically did not pick up nitazenes when they are present in low concentrations. However, even these low concentrations of nitazenes can make heroin much more dangerous.”
While not as well-known as fentanyls, which have gained notoriety due to their role in America’s drug death crisis and which President Trump has used as justification for policies relating to immigration and tariffs, nitazenes are more common in the UK.
Nitazenes are highly potent synthetic opioids and some are actually more dangerous for individuals than fentanyls. The presence of nitazenes in the heroin supply increases the risk of overdose and death.
The Office for Health Improvement and Disparity reported 179 deaths involving one or more nitazenes between June 2023 and May 2024, although this is likely to be an underestimate.
In Scotland, toxicology reports show a growing number of suspected nitazene-related deaths. In response, Public Health Scotland issued a RADAR (Rapid Action Drug Alerts and Response) alert in April 2024, warning healthcare providers and harm reduction services about the increased presence and dangers of nitazenes in the unregulated drug supply.
Dr Marland continued, “These results show that while it is important that individuals are able to test their drugs prior to use, it is equally important that drug testing strips like these are properly validated to understand their limitations.
“Thousands of these strips have been provided to individuals to date and, while it is positive that so many are embracing harm reduction services, it is critical that we maintain the confidence of service users.”
The Dundee paper is published in the journal Harm Reduction.