Characterization of growth hormone secretagogue small molecule ibutamoren (MK-0677) and its possible metabolites in thoroughbred horses for doping control.
Level 5 - mechanism / opinion, no new human data
Animal pharmacology and metabolism study with no human data
PubMed 35716382 · doi:10.1002/rcm.9337
What was done
Thoroughbred horses were orally administered the growth hormone secretagogue ibutamoren (MK-0677) to profile drug metabolism for doping control. Liquid chromatography/high-resolution mass spectrometry was used to determine the probable structures of detected metabolites.
What was found
A total of 22 metabolites were identified (17 phase I and 5 phase II metabolites), including mono- and di-hydroxylated forms, dissociated side chains (benzyl group and 2-amino-2-methylpropanamide), hydrogenated metabolites, and glucuronic acid conjugates (no sulfonic acid conjugates were observed). The parent drug ibutamoren was detectable for up to 72 hours, while major metabolites remained detectable for up to 96 hours following a single dose.
Why it matters
This establishes metabolic targets and detection windows to support anti-doping surveillance for ibutamoren abuse in thoroughbred horse racing.
Limits
The abstract does not disclose the sample size (number of horses), the dose administered, the matrix analyzed (e.g., plasma, urine), or quantitative limits of detection. Findings in horses do not translate to human metabolism.
Cited by
- supports MK-677 (ibutamoren) is a non-peptide growth hormone secretagogue and ghrelin receptor agonist.