Our research shows that counterfeit diazepam tablets can be highly unpredictable and dangerous. While some tablets contained large amounts of diazepam, many didn’t contain any diazepam at all. This makes it very easy for people to accidentally take too much or mix harmful substances without knowing. By developing faster and more portable ways to test drugs, we hope to help reduce harm and keep people safer."
Dr Vincenzo Abbate, Reader in Bioanalysis at King’s
02 December 2025
Study finds wide variation in strength and content of illicit diazepam tablets
A study from King’s, in collaboration with TICTAC Communications and Nanalysis, tested seized tablets containing the sedative diazepam and found considerable variation in strength and content, highlighting the dangers of recreational drug use.
The researchers analysed 100 illicit diazepam tablets collected over a 25-year period and learned that the most potent tablets were over 50 times stronger than the weakest, and that many contained potentially harmful cutting agents. The study, published in the Quantitative NMR Journal, underscores the risks associated with using potentially counterfeit tablets.
Benzodiazepines are a class of drugs that includes the drug diazepam and are primarily prescribed for their sedative effects to treat conditions such as panic disorder, anxiety, insomnia and epilepsy. However, their recreational use is a growing concern. They can lead to dependence, withdrawal symptoms, and impairment of the central nervous system.
Non-medical use of benzodiazepines continues to rise, with tablets often sourced online. These products are frequently mislabelled and may contain inconsistent doses or harmful cutting agents, increasing the risk of overdose and dependence. Diazepam content found in street tablets has fluctuated over time, influenced by a range of external factors. For example, stagnation in the illegal drugs market following the COVID-19 pandemic may have contributed to the decrease of diazepam content observed in recent years.
The study analysed 100 diazepam tablets seized between the years 1998 and 2023. The samples were investigated by TICTAC, a leading provider of drug information and identification, and King’s researchers. The analysis revealed a large variability in active content, from 0.52 mg to 26.25 mg per tablet, with some samples containing no detectable diazepam.
One key aspect of the study involved testing the suitability of using a small, portable machine to analyse drug samples in the field. Using quantitative NMR (qNMR) spectroscopy, the team developed and validated a benchtop NMR method capable of accurately identifying and quantifying diazepam in seized street samples. The benchtop system was tested as a portable alternative to traditional high-field NMR instruments, offering reliable performance with lower cost and simpler operation.
The variability observed in street samples highlights the need for ongoing market monitoring and surveillance of emerging drug trends. This study’s validation confirmed that benchtop qNMR is a reliable and effective method for analysing diazepam content in illicit tablet samples.
The researchers note that future work will focus on expanding the sample size and adapting the method to detect other benzodiazepins, to improve sensitivity and further enhance the accuracy of field-based drug testing.
This research follows on from another study conducted by TICTAC and Dr Abbate’s team that explored the content of ecstasy, also known as MDMA, tablets. Published in the Journal of Pharmaceutical and Biomedical Analysis in 2022, the study found variability in MDMA dosage in ecstasy tablets but also a significant increase in potency between the years 2018 and 2019.
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Reader in Bioanalysis