N-Ethylpentedrone: first hair detection and human metabolic profiling across multiple biological matrices using...

N-ethylpentedrone (NEP) is a New Psychoactive Substance (NPS) of the cathinone class that has raised public health concerns, scheduled by both the United Nations Office on Drugs and Crime and the European Union Drugs Agency, since 2024. We report here a fatal case involving a 29-years-old man who used NEP in a chemsex context. Three plastic bags containing off-white to beige powders and crystals were found near the body. Proton and carbon nuclear magnetic resonance spectrometry (¹H and ¹³C NMR) and ultra-high performance liquid chromatography-high-resolution mass spectrometry (UHPLC-HRMS) analyses confirmed all three bags contained NEP with purity above 98%. UHPLC-HRMS data analyses using molecular networking and in silico prediction allowed to propose NEP metabolic profile in peripheral and cardiac blood, bile, gastric fluid, urine and hair. We described here six Phase I metabolites, and we proposed NEP (C₁₃H₁₉NO) as the principal biomarker in NEP intake, metabolites M4 (C₁₁H₁₇NO) and M1 (C₁₁H₁₅NO) serving as biomarkers of consumption, as all of which were detected in all postmortem body fluid samples as well as in hair. Predominant metabolic pathways involved keto-reduction, N-dealkylation, hydroxylation, and oxidation, while no Phase II metabolites were detected under the applied analytical conditions. NEP was quantified at 18 mg/L and 20 mg/L in peripheral and cardiac blood, respectively, and 654-755 pg/mg in hair. These exceptionally high concentrations in biological fluids indicate an acute NEP intoxication, while hair analyses confirm repeated exposure over several months, consistent with chronic use. In summary, the identification of these metabolites in various postmortem body fluid matrices and in hair will improve our understanding of potential drug consumption markers and contribute to better monitoring and detection of N-ethylpentedrone use and abuse.