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The selective androgen receptor modulators are a recent class of anabolic agents, used to improve athletic performance. Among these molecules, there is (2 S)-N-(4-cyano-3-trifluoromethylphenyl)− 3-(3-fluoro-4-chlorophenoxyl)2-hydroxy-2-methyl-propanamide, commonly known as S-23. This molecule appeared very recently on the doping market. As a result, very few data are available in the literature, and nothing has been published about long-term effects of S-23. The authors focused on the detection of S-23 and its metabolites in human urine, following a single oral administration of approx. 8 mg to a volunteer, using standard ultra-performance liquid chromatography-triple quadrupole-mass spectrometry (UPLC-MS/MS), and ultra-performance liquid chromatography-quadrupole time of flight-mass spectrometry (UPLC-Q-TOF-MS). To the best of the authors knowledge, this seems to be the first study ever achieved on S-23. In vitro experiment was performed, using human liver microsomes, in order to investigate the potential CYP- and UGT-dependent S-23 metabolites. Four metabolites were produced, which were identified as hydroxy-S-23 (C 18 H 12 O 4 N 2 ClF 4 : m/z [M-H-] 431.0423); O -dephenylate-S-23 (C 12 H 10 O 3 N 2 F 3 : m/z [M-H-] 287.0647); S-23-glucuronide (C 24 H 20 O 9 N 2 ClF 4 : m/z [M-H-] 591.0794) and hydroxy-S-23-glucuronide (C 24 H 20 O 10 N 2 ClF 4 : m/z [M-H-] 607.0743). After consumption of S-23, the parent drug was detectable in hydrolyzed urine from 2 h post administration up to 28 days, with concentrations ranging between 0.5 and 93 ng/mL. In the urine, only one of the four metabolites identified in vitro was detected, hydroxy-S-23. This metabolite was detected up to 28 days. It does not seem to increase the window of detection of S-23 as the ratio between hydroxy-S-23 and the parent drug was always lower than 1. Another metabolite, dihydroxy-S-23, not identified in vitro, was identified in the urine of the volunteer. Hair sample, collected one month after the consumption of a single tablet, was negative for S-23 and hydroxy-S-23, with a LOQ at 0.1 pg/mg. [Display omitted] • The authors focused on the detection of S-23 and its metabolites in human urine, following a oral administration of 8 mg. • Four metabolites were produced in vitro, using human liver microsomes. • Parent S-23 was detectable in hydrolyzed urine up to 28 days. • Hydroxy-S-23 was detected up to 28 days, in urine. Dihydroxy-S-23 was detected from + 8 hours up to 5 days. • Hair sample, collected one month after the exposure, was negative for S-23 and metabolites, with a LOQ at 0.1 pg/mg. [ABSTRACT FROM AUTHOR]