Blood concentrations of new designer benzodiazepines in forensic cases

A number of new designer benzodiazepines have reached the illegal drug market over the past years. Toxicological interpretation of concentrations of these drugs in blood is quite challenging as very limited human data have previously been published. The aim of this study was to report blood concentrations of new designer benzodiazepines in a population of drugged drivers as well as some other criminal offenders, and to relate this to clinical impairment.

The present material represents cases involving new designer benzodiazepines (clonazolam, diclazepam, flubromazepam, flubromazolam and pyrazolam) and etizolam, submitted for analyses during the period July 1, 2013-May 31, 2016. Analyses were performed using an ultra-performance liquid chromatography-tandem mass spectrometry method. Blood concentrations and results from the clinical test of impairment are reported.

New designer benzodiazepines were detected in 77 cases during the study period. The median (range) concentrations were 0.012mg/L (0.00048-0.10) for flubromazolam (n=25), 0.055mg/L (0.0047-1.2) for flubromazepam (n=24), 0.013mg/L (0.0021-0.057) for diclazepam (n=15), 0.050mg/L (0.019-0.17) for etizolam (n=14), 0.0053mg/L (0.0019-0.011) for clonazolam (n=7) and 0.074mg/L for pyrazolam (n=1). In six cases, designer benzodiazepines were the only drugs detected in blood, and in two of those cases, the physician had given the conclusion of "considerably impaired" upon performing the clinical test for impairment.

Given the lack of previously published data on human concentrations, results presented in this study could be helpful in interpretation of blood concentrations of new designer benzodiazepines. This is crucial for the assessment of the importance of toxicological results in suspected drugged drivers, rape victims, etc.