Biotransformation of 17-alkyl steroids in the equine: high-performance liquid chromatography-mass spectrometric and gas chromatography-mass spectrometric analysis of fluoxymesterone metabolites in urine samples.

In this study the equine metabolism of fluoxymesterone (9alpha-fluoro-11beta-17beta-dihydroxy-17alpha-meth ylandrost-4-ene-3-one) given orally has been investigated. The parent material was not detected, but two major 16-hydroxy metabolites which corresponded to a mono- and a di-hydroxylation product were evident. One of the hydroxylation positions was identified as C-16. Phase II metabolism in the form of glucuronide formation was also common. These steroids will provide target compounds for confirming abuse of this drug in the horse.

Testing for fluoxymesterone (Halotestin) administration to man: identification of urinary metabolites by gas chromatography-mass spectrometry.

Fluoxymesterone, an anabolic steroid, is metabolized in man primarily by 6 beta-hydroxylation, 4-ene-reduction, 3-keto-reduction, and 11-hydroxy-oxidation. These pathways of metabolism are suggested by the positive identification of 4 metabolites and the tentative identification of 3 other metabolites. Detection of the drug in urine is possible for at least 5 days after a single 10 mg oral dose to previously untreated adult males, by monitoring the presence of 2 metabolites, since the parent drug is not detectable more than 1 day after the dose.