Large scale consumption monitoring of benzodiazepines and z-drugs by hair analysis

Benzodiazepines (BDZ) and z-drugs belong to the most frequently prescribed medicines worldwide used for anxiety, epilepsy and sleeping disorders. Due to their pharmacology, they have a high potential for misuse. Hair analysis is being performed for the retrospective monitoring of drug exposure. However, there is a lack of reference values to obtain indication of BDZ/z-drug misuse. Further, there is no consensus on BDZ/z-drug cut-off concentrations above which a hair sample is reported as positive. The objective of the present study was to retrospectively evaluate BDZ/z-drug levels in hair for better interpretation of hair testing results. For this purpose, 4,630 authentic samples (head/body hair) from a heterogeneous cohort in Switzerland tested for the presence of 20 BDZ/BDZ metabolites and three z-drugs by liquid chromatography-tandem mass spectrometry were included. Drug concentrations in hair were statistically evaluated by box-plots in 1,726 positive samples. Further, metabolite-to-parent drug ratios were determined. Zolpidem, diazepam, nordazepam, oxazepam, lorazepam, midazolam, alprazolam, and bro-mazepam were among the most frequently detected drugs. Generally, drug concentration ranges varied strongly between the lower limit of quantification and 30,000 pg/mg hair. Sixteen BDZ/BDZ metabolites and zopiclone (z-drug) displayed a median below 50 pg/mg which is recommended as cut-off or minimum requirement for the limit of detection (LOD) by institutions. In case of ten drugs even the 75th percentile was below 50 pg/mg. Therefore, we strongly recommend to reconsider whether the use of an equal BDZ/z-drug cut-off is reasonable and whether minimum requirements for LODs should be lowered. The statistical evaluation of BDZ/Z-drug hair concentrations by box-plots can help in the development of analytical methods for hair samples and in the interpretation of BDZ/z-drug hair levels. (C) 2020 Published by Elsevier B.V.