Detection of the designer benzodiazepine metizolam in urine and preliminary data on its metabolism: Metizolam identification in urine

TLDR: The most relevant potential CYP- and UGT-dependent metabolites of metizolam were investigated in vitro using human liver microsome incubation and, subsequently, liquid chromatography coupled with quadrupole-time of flight mass spectrometry (UHPLC-Q-TOF-MS) analysis.

Abstract: Designer benzodiazepines provide an attractive alternative to prescribed benzodiazepines for abuse purposes as they are readily available via the Internet without control. Metizolam was ordered via the Internet and a 2 mg blue tablet was orally administered to a 54-year-old man. Urine samples were collected over 6 days in polypropylene tubes. After liquid/liquid extraction at pH 9.5, metizolam was analyzed by ultra-performance liquid chromatography-electrospray ionization-tandem mass spectrometry (UPLC-ESI-MS/MS) using a standard method devoted to benzodiazepines, and ions transitions, at m/z 328.9 > 275.0 and 328.9 > 300.0. Metizolam was detectable in hydrolyzed urine during the 46-h period, with concentrations always lower than 11 ng/mL. About 0.3% of the initial dose was excreted in urines as total unchanged metizolam during the first 24 h. The most relevant potential CYP- and UGT-dependent metabolites of metizolam were investigated in vitro using human liver microsome incubation and, subsequently, liquid chromatography coupled with quadrupole-time of flight mass spectrometry (UHPLC-Q-TOF-MS) analysis. Three mono-hydroxylated metabolites were produced including a hydroxylation compound at the 2-ethyl moiety of metizolam (M1) as quantitatively main metabolite, and a N-hydroxymetiazolam (M2). The structure of the third metabolite (M3) could not be elucidated because of a too low experimental production rate. Two authentic urine samples were analyzed using the same analytical method to search for metabolites of metizolam. M1, together with its glucuronide (M1-Glu), and M2 were observed in urine at the 8 h mark, whereas only M1 and M1-Glu were still detected in urine at 30 h post administration. Copyright © 2016 John Wiley & Sons, Ltd.