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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]

• Letrozole can be diverted from its therapeutic use. • Letrozole counteracts feminizing effects due to anabolic steroids abuse. • Hair is the specimen of choice to document long-term drug exposure. • Two independent methods (LC-MS/MS and LC-HRMS) are essential for legal rules. Letrozole is a reversible aromatase inhibitor, used in the treatment of hormone-dependent woman cancer. No indication for medical use is available for men. In recent years, several cases of doping with letrozole have been observed, especially among high level athletes. Aromatase inhibitors reverse the harmful effects (feminizing) of the abuse of anabolic androgenic steroids. Letrozole is included on the list of products prohibited in- and out-competition by the World Anti-Doping Agency, under section S4.1. The aim of the present work was to develop a specific method to identify letrozole in human hair of a male amateur athlete by LC-MS/MS and confirmation by LC-HRMS, after incubation of 20 mg of matrix in 1 mL of methanol. The chromatographic separation was performed using a reverse phase column HSS C18 with a gradient elution of 15 min (from 87% to 5% of formate buffer adjusted to pH 3). Linearity was observed from 1 to 1000 pg/mg (r2 = 0.9999), after spiking blank hair with the corresponding amounts of letrozole. The limit of detection was estimated at 0.5 pg/mg and the lower limit of quantification was the first point of the calibration curve, i.e. 1 pg/mg. The precision was lower than 20% and there was no interference with the analytes by chemicals or any extractable endogenous materials present in hair. Letrozole was identified in the male amateur athlete hair at 310 pg/mg (segment 0–2 cm) and 245 pg/mg (segment 2–4 cm). [ABSTRACT FROM AUTHOR]