Researchers at the University of Dundee have published findings revealing serious limitations in the reliability of nitazene test strips currently distributed across the United Kingdom. Furthermore, their study in Harm Reduction Journal examined Rapid Response™ Nitazene Test Strips manufactured by BTNX against 36 different nitazene compounds and 93 other substances.

The research team, led by Victoria Marland, Lorna Nisbet, and Niamh Nic Daéid, tested these strips under controlled laboratory conditions. Moreover, they also analysed authentic seized heroin samples from Scottish prisons to assess real-world performance.

Key findings on nitazene test strips detection rates

The study found that nitazene test strips detected only 28 out of 36 nitazene compounds tested, representing a 78% success rate. Consequently, eight nitazene variants went completely undetected, including metodesnitazene, etazene, protodesnitazene, and 5-aminoisotonitazene.

Significantly, the Office of Health Improvement and Disparities reported metodesnitazene in at least one death in England in 2024. Additionally, the Welsh Emerging Drugs and Identification of Novel Substances Project (WEDINOS) identified etazene in 2021, confirming that these undetectable compounds circulate in UK drug supplies.

Furthermore, researchers discovered dramatic variations in detection sensitivity across different nitazene compounds. Indeed, the limit of detection ranged from 250 nanograms per millilitre for N-desethyl metonitazene to 100,000 nanograms per millilitre for certain other variants—a 400-fold difference in sensitivity.

Understanding detection limits of nitazene test strips

The manufacturer BTNX reports detection limits of 2,000 ng/mL for isotonitazene, 3,000 ng/mL for protonitazene, and 1,300 ng/mL for N-pyrrolidino etonitazene. However, the University of Dundee study found slightly different values: 1,500 ng/mL for isotonitazene, 3,000 ng/mL for protonitazene, and 1,500 ng/mL for N-pyrrolidino etonitazene.

Moreover, researchers identified that specific structural modifications affect detection capability. Notably, removing the 5-nitro group from nitazene compounds—creating ‘desnitazenes’—prevents nitazene test strips from detecting these variants entirely. Therefore, metodesnitazene, protodesnitazene, and N-pyrrolidino metodesnitazene all produced false negative results.

Additionally, lengthening the alkyloxy group appears to increase detection limits. For instance, metonitazene showed a detection limit of 1,000 ng/mL whilst protonitazene required 3,000 ng/mL—three times higher despite similar chemical structures.

Caffeine causes false positives in nitazene test strips

Beyond detection failures, researchers discovered that caffeine—one of the most common adulterants in street drugs—causes significant interference with nitazene test strips. Indeed, the study found no cross-reactivity at 100,000 ng/mL (100 µg/mL), but interference began at approximately 300,000 ng/mL (300 µg/mL).

Furthermore, complete false positive results occurred between 7,000,000 and 10,000,000 ng/mL (7-10 mg/mL) of caffeine. Consequently, when researchers tested three authentic seized heroin samples from Scottish prisons, all showed faded test lines suggesting potential false positives.

Subsequent analysis revealed these samples contained no nitazenes but had estimated caffeine content of 21.9% to 24.9% of total sample weight. Therefore, when researchers dissolved approximately 1 milligram of these samples in 1 millilitre of water—following typical testing procedures—caffeine concentrations reached 219,000 to 249,000 ng/mL, approaching the interference threshold.

Moreover, the nitazene test strips showed no cross-reactivity with 93 other tested substances at 100 µg/mL, including 26 non-nitazene opioids, 30 synthetic cannabinoids, and 15 benzodiazepines. However, the caffeine interference remains problematic given its prevalence in street heroin, cocaine, and amphetamines.

Real-world implications of nitazene test strips limitations

The researchers tested whether other drugs interfere with nitazene detection by preparing solutions containing 1,300 ng/mL metonitazene combined with 100,000 ng/mL of other commonly encountered substances. Indeed, nitazene test strips successfully detected metonitazene in all mixtures tested, including combinations with diamorphine, caffeine, paracetamol, and various benzodiazepines.

However, this finding must be balanced against the detection limit variations and false negative risks. Significantly, if a nitazene compound has a detection limit of 100,000 ng/mL (like some variants the team tested), whilst other drugs occur at similar concentrations, the strips may fail to identify the nitazene.

Additionally, researchers noted that diluting samples to avoid caffeine interference carries inherent risks. Therefore, whilst reducing caffeine concentration might prevent false positives, this approach simultaneously dilutes any nitazenes present, potentially reducing their concentration below detection thresholds.

Scotland’s context: rising nitazene deaths

This research carries particular urgency given Scotland’s drug death statistics. Furthermore, Scotland recorded 1,197 suspected drug-related deaths in 2023, representing a 12% increase from 2022. Moreover, opiates played a role in 80% of these deaths.

Whilst authorities detected nitazenes in a small proportion—31 deaths (2.6%) in 2023 compared to just one death (0.1%) in 2022—this represents a concerning upward trend. Indeed, between January and March 2025, Public Health Scotland detected nitazenes in 38 deaths across Scotland alone.

Therefore, accurate detection methods become increasingly critical as these compounds appear more frequently in drug supplies. However, the University of Dundee study demonstrates that current nitazene test strips cannot reliably identify all variants circulating in the market.

Scientific recommendations on nitazene test strips deployment

The research team concluded that “caution should be exercised when deploying these nitazene test strips as frontline presumptive tests in both criminal justice and public health contexts due to the observed false negative and false positive results.”

Furthermore, they emphasised that scientists should not make assumptions about detection limits of emerging nitazene analogues based solely on chemical structure. Indeed, the study revealed inconsistent patterns—for example, N-piperidinyl substitution increased detection limits from 250 to 1,000 ng/mL for metonitazene variants but produced different effects on isotonitazene variants.

Moreover, researchers stressed the need for ongoing validation as new nitazene compounds emerge. Therefore, test strips that work today may prove inadequate tomorrow as drug markets evolve and manufacturers create new variants to circumvent detection.

Ultimately, the study highlights that whilst nitazene test strips may detect some compounds under certain conditions, their 22% failure rate, sensitivity variations, and caffeine interference pose significant accuracy concerns. Consequently, anyone relying on these devices should understand their substantial limitations and the risks of both false negative and false positive results.

Source: dbrecoveryresources