A Study of the Metabolism of Ibutamoren (MK-677), a Growth Hormone Secretagogue, in Human Urine by Ultra-High-Performance Liquid Chromatography–High-Resolution Mass Spectrometry

The metabolism of Ibutamoren (MK-677), a nonpeptide growth hormone secretagogue, was investigated by analyzing human urine samples collected over 2 weeks following a single oral administration of the drug. Sample preparation involved dilution and enzymatic hydrolysis followed by a liquid–liquid extraction. Compounds were detected by reversed-phase ultra-high-performance liquid chromatography with quadrupole–time-of-flight mass spectrometric detection, using electrospray ionization in the positive ion mode. In the urine samples, the unchanged compound and its metabolites were identified. The hydroxylated analyte can be detected 4 days after a single oral administration of the compound, making it a promising target for detection.