Oxandrolone disposition and metabolism in man

The disposition and metabolic fate of 14 C‐oxandrolone (17α‐methyl‐17β‐hydroxy‐2‐oxa‐5α‐androstan‐3‐one) has been studied in 6 healthy male subiects. After administration of a single oral dose (10 mg containing 20 p.Ci of 14C in ethanolic solution), the peak concentration of 14 C‐oxandrolone in the plasma was 417 (mean) µg per milliliter at 0.50 to 1.50 hours. Its level then declined in two phases: from 1.5 to 4.0 hours with a half‐life of 0.55 hour and from 4.0 to 48 hours with a half‐life of 9.4 hours. The ingested 14 C was eliminated predominantly by urinary excretion. In the urine, 43.6% of the administered 14 C was excreted in 24 hours and 60.4% in 96 hours. Recovery of 14 C in the feces accounted for only 2.8% of the dose. The chloroform extractable urinary radioactivity was largely composed of the unchanged drug, which accounted for 46.1 % of urinary 14 C or 28.7% of the illgested 14 C. Enzyme hydrolysis of the urinary coniugated fraction, which accounted for 31.3% of the urinary 14 C, gave two major aglycones in the approximate ratio of 2:7. These aglycones were tentatively identified as oxandrolone and 16β‐hydroxyoxandrolone, respectively.