Article original / Original article Méthoxyisoflavone et dépistage du cannabis dans les urines : mise en évidence d'une réaction croisée peu connue Methoxyisoflavone and urine cannabinoid screening: evidence of a poorly known cross-reactivity

Objectives: Methoxyisoflavone (5-methyl-7-methoxyisoflavone) is a dietary supplement employed by bodybuilders. Following a false positive result in a urinary cannabinoid screening test in the context of methoxyisofla- vone use, this active ingredient and its metabolites are searched for in the urine sample to objectivize a possible cross- reactivity with the antibody screening test. An administration trial in healthy volunteers is also performed. Methods: After enzymatic hydrolysis, the urine sample is prepared by liquid-liquid extractions in acidic (pH 4) and basic (pH 9) conditions and then different analytical techniques are used: high-performance liquid chromatography-electrospray ionization-mass spectrometry (LC-ESI-MS) operating in positive ionization mode (sampling cone voltage 70 V) and gas chromatography coupled with mass spectrometry (GC/MS) after derivatization by acetylation and silylation. A ref- erence solution of 5-methyl-7-methoxyisoflavone is analyzed under the same conditions. The administration trial was conducted in three healthy volunteers receiving orally 300 mg of methoxyisoflavone every 12 hours for 36 hours. A