Metabolism of Six Novel Nitazenes in Human Liver Microsomes Based on Ultra-High-Performance Liquid Chromatography Coupled With High-Resolution Mass Spectrometry.

Synthetic opioids are a chemically diverse group of substances that function as central nervous system depressants, among which the 2-benzylbenzimidazole derivatives, also known as nitazenes or nitazene analogs, have recently emerged into the recreational market. The detection of these substances in biological samples largely relies on the acquisition of metabolic data. In this study, the first-phase metabolism patterns of methylenedioxynitazene, N-desethyl etonitazene, N-desethyl methylenedioxynitazene, ethyleneoxynitazene, N-pyrrolidino etonitazene, and N-desethyl isotonitazene utilizing human liver microsomes were investigated, and the metabolites were characterized through high-performance liquid chromatography-high-resolution tandem mass spectrometry. Two to eleven metabolites were identified for different nitazene analogs. It was observed that N-dealkylation, hydroxylation, and dehydrogenation were the major metabolic reactions, with other noteworthy metabolic reactions such as reduction, oxidation, and their combinations also identified. Therefore, it is recommended to use N-dealkylation and hydroxylation metabolites as analytical markers for monitoring of the intake of these substances.