Studies on anabolic steroids. II--Gas chromatographic/mass spectrometric characterization of oxandrolone urinary metabolites in man.

The metabolism of 17 alpha-methyl-17 beta-hydroxy-2-oxa-5 alpha-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 16 alpha- and 16 beta-hydroxyoxandrolone and a delta-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.