Identification of etazene (etodesnitazene) metabolites in human urine by LC‐HRMS

Etazene (or etodesnitazene) is a novel and highly active synthetic opioid belonging to the rapidly evolving and emerging group of “nitazenes.” Etazene metabolites were identified through analysis of a human urine sample. The sample was obtained from a 25‐year‐old man who attempted suicide by taking a new psychoactive substances (NPS) cocktail purchased online and was analyzed by ultrahigh performance liquid chromatography‐high‐resolution mass spectrometry (UHPLC‐HRMS). Etazene metabolites were predicted with BioTransformer 3.0, and the exact masses were added to the inclusion list. Eight possible metabolites were identified in the urine sample. N‐ and O‐deethylation were identified as the predominant metabolism routes, resulting in M1 (O‐deethylated etazene; most abundant metabolite based on the peak area), M2 (N‐deethylated etazene), and M3 (N,O‐dideethylated etazene) metabolites. Less abundant hydroxylated products of these deethylated metabolites and etazene were also found. Additionally, in the analysis without β‐glucuronidase treatment, M1‐ and M3‐glucuronide phase II metabolites were found. As N‐ and O‐deethylated products seem to be the predominant urinary metabolites, the detection of these metabolites in urine can be useful to demonstrate etazene exposure. Examination of the in vivo metabolism of etazene, a highly active synthetic opioid belonging to the emerging group of nitazenes, was performed through HRMS analysis of an authentic human urine sample. Appropriate metabolites are proposed to use as urinary biomarkers for etazene exposure.