Studies on anabolic steroidsII—gas chromatographic/mass spectrometric characterization of oxandrolone urinary metabolites in man

Abstract

The metabolism of 17α-methyl-17β-hydroxy-2-oxa-5α-androstan-3-one (oxandrolone) in man has been investigated by gas chromatography/mass spectrometry. After oral administration of a 10 mg dose to man, five metabolites were detected in the free fraction of the urinary samples. Oxandrolone, the major compound excreted in urine, was detected within 72 h after administration. During this period 35.8 and 8.4% of the administered dose was excreted as unchanged oxandrolone and 17-epioxandrolone, respectively. In addition, minute amounts of 16α- and 16β- hydroxyoxandrolone and a δ-hydroxy acid resulting from the hydrolysis of the lactone group of oxandrolone were detected in the urine samples 8–60 h after administration. Furthermore, the susceptibility of oxandrolone to hydrolysis was investigated under several pH conditions. Extraction and fractionation of steroidal metabolites was achieved by using C₁₈ and silica Sep Pak™ chromatography. The mass spectra of the metabolites are presented and major fragmentation pathways discussed.