Metabolism of formestane in humans: Identification of urinary biomarkers for antidoping analysis.

Formestane (4-hydroxyandrost-4-ene-3,17-dione, 4OH-AED) is an aromatase inhibitor prohibited in sports. In recent years, it has been demonstrated that it can also originate endogenously by the hydroxylation in C4 position of androstenedione. Thus, the use of isotope ratio mass spectrometry (IRMS) is mandatory according to the World Antidoping Agency (WADA) to discriminate endogenous from synthetic origin. In a previous work and after oral administrations of formestane (4OH-AED), the ratio between the main formestane metabolite (4α-hydroxyepiandrosterone; 4OH-EA) and formestane parent compound could help to identify the endogenous origin, avoiding unnecessary and costly IRMS confirmations. In the present work, we investigated whether the same criteria could also be applied after transdermal applications. Six volunteers were transdermally treated once with formestane. Urine samples were collected for 120 h postadministration and analyzed by gas chromatography coupled to mass spectrometry (GC-MS and GC-MS/MS). Formestane and its major metabolites were monitored. The kinetic profile of formestane and its main metabolites was found different between oral and transdermal application. A shift on the excretion of the metabolites compared to formestane itself that can be observed after the oral administration, is absent after the transdermal one. This makes that a simple criteria cannot be applied to differentiate the endogenous from the synthetic origin based on metabolic ratios. The ratio between 4-hydroxyepiandrosterone and 4-hydroxyandrosterone (4OH-A) can be used to differentiate the route of administration. Ratios higher than one (4OH-EA/4OH-A > 1) are diagnostic of an oral administration. This allows to correctly interpret the 4OH-EA/4OH-AED ratio as proposed in our previous investigation. The results of this work demonstrate that the use of appropriate biomarkers (metabolic ratios) helps to reach correct conclusions without using complex and costly instrumentation approaches.

Determination of flumethasone in calf urine and serum by liquid chromatography-tandem mass spectrometry.

Corticosteroids can be illegally administered to cattle as growth promoting agents to improve meat production. We developed a liquid chromatography-atmospheric pressure ionization mass spectrometry-mass spectrometry (LC-MS-MS) method able to identify and quantify flumethasone, one of the most potent fluorinated synthetic corticosteroid, in serum and urine from treated calves. The analyte was purified from urine (conjugated and free, following enzymatic hydrolysis) and from serum by C18 solid-phase and liquid-liquid extractions, then analyzed by LC-MS-MS monitoring the product ions of an abundant precursor (SRM in negative ionization mode). Results on flumethasone residues in biological fluids in three calves treated at different levels are presented. This method allowed the detection of flumethasone in bovine urine and serum at the 30-pg/ml level.