TY - JOUR T1 - Detection and Characterization of a New Metabolite of 17α-Methyltestosterone JF - Drug Metabolism and Disposition JO - Drug Metab Dispos SP - 2153 LP - 2162 DO - 10.1124/dmd.109.028373 VL - 37 IS - 11 AU - Óscar J. Pozo AU - Peter Van Eenoo AU - Koen Deventer AU - Leen Lootens AU - Wim Van Thuyne AU - Maria K. Parr AU - Wilhelm Schänzer AU - Juan V. Sancho AU - Felix Hernández AU - Philip Meuleman AU - Geert Leroux-Roels AU - Frans T. Delbeke Y1 - 2009/11/01 UR - http://dmd.aspetjournals.org/content/37/11/2153.abstract N2 - The misuse of the anabolic steroid methyltestosterone is currently routinely monitored in doping control laboratories by gas chromatography-mass spectrometry (GC-MS) of two of its metabolites: 17α-methyl-5β-androstane-3α,17β-diol and 17α-methyl-5α-androstane-3α,17β-diol. Because of the absence of any easy ionizable moiety, these metabolites are poorly detectable using liquid chromatography-tandem mass spectrometry (LC-MS/MS) with electrospray ionization (ESI). In this study, the metabolism of methyltestosterone has been reinvestigated by the use of a precursor ion scan method in LC-ESI-MS/MS. Two metabolites have been detected using this method. Both compounds have been confirmed in postadministration urine samples of an urokinase plasminogen activator-severe combined immunodeficiency (uPA-SCID) mouse with humanized liver and were characterized by LC-MS/MS and GC-MS using both quadrupole and time of flight analyzers. From the detailed study of the fragmentation, these metabolites were proposed to be epimethyltestosterone and a dehydrogenated compound. Epimethyltestosterone has previously been described as a minor metabolite, whereas the occurrence of the oxidized metabolite has not been reported. Comparison with the synthesized reference revealed that the structure of the dehydrogenated metabolite is 6-ene-epimethyltestosterone. A selected reaction monitoring method including three transitions for each metabolite has been developed and applied to samples from an excretion study and to samples declared positive after GC-MS analysis. 6-Ene-epimethyltestosterone was found in all samples, showing its applicability in the detection of methyltestosterone misuse. Copyright © 2009 by The American Society for Pharmacology and Experimental Therapeutics ER -