Kantonsspital St.Gallen
login

Characterization and in vitro phase I microsomal metabolism of designer benzodiazepines: An update comprising flunitrazolam, norflurazepam, and 4'-chlorodiazepam (Ro5-4864)

Björn Moosmann, Philippe Bisel, Folker Westphal, Maurice Wilde, Jürgen Kempf, Verena Angerer & Volker Auwärter

abstract The number of newly appearing benzodiazepine derivatives on the new psychoactive substances (NPS) drug market has increased over the last couple of years totaling 23 'designer benzodiazepines' monitored at the end of 2017 by the European Monitoring Centre for Drugs and Drug Addiction. In the present study, three benzodiazepines [flunitrazolam, norflurazepam, and 4'-chlorodiazepam (Ro5-4864)] offered as 'research chemicals' on the Internet were characterized and their main in vitro phase I metabolites tentatively identified after incubation with pooled human liver microsomes. For all compounds, the structural formula declared by the vendor was confirmed by gas chromatography-mass spectrometry (GC-MS), liquid chromatography-tandem mass spectrometry (LC MS/MS), liquid chromatography-quadrupole time of flight-mass spectrometry (LC-QTOF-MS) analysis and nuclear magnetic resonance (NMR) spectroscopy. The metabolic steps of flunitrazolam were monohydroxylation, dihydroxylation, and reduction of the nitro function. The detected in vitro phase I metabolites of norflurazepam were hydroxynorflurazepam and dihydroxynorflurazepam. 4'-Chlorodiazepam biotransformation consisted of N-dealkylation and hydroxylation. It has to be noted that 4'-chlorodiazepam and its metabolites show almost identical LC-MS/MS fragmentation patterns to diclazepam and its metabolites (delorazepam, lormetazepam, and lorazepam), making a sufficient chromatographic separation inevitable. Sale of norflurazepam, the metabolite of the prescribed benzodiazepines flurazepam and fludiazepam, presents the risk of incorrect interpretation of analytical findings.
   
citation Moosmann B, Bisel P, Westphal F, Wilde M, Kempf J, Angerer V, Auwärter V. Characterization and in vitro phase I microsomal metabolism of designer benzodiazepines: An update comprising flunitrazolam, norflurazepam, and 4'-chlorodiazepam (Ro5-4864). Drug Test Anal 2019; 11:541-549.
   
type journal paper/review (English)
date of publishing 05-02-2019
journal title Drug Test Anal (11/3)
ISSN electronic 1942-7611
pages 541-549
PubMed 30578721
DOI 10.1002/dta.2561