Detection of the growth hormone secretagogue MK-0677 in equine hair following oral administration.
MK-0677 can be detected in equine hair for up to 358 days after administration, indicating potential for long-term monitoring in doping control.
Where it sits
this study against the rest of the mk-677 (ibutamoren) corpusSummary and findings
This study investigated the detection of MK-0677 (ibutamoren) in equine hair following oral administration to a Thoroughbred racehorse. MK-0677 was detected in hair samples for up to 209 days in mane and 358 days in tail. The study aimed to assess internal incorporation versus external deposition of the compound.
Abstract
MK-0677 (ibutamoren) is an orally active non-peptide growth hormone secretagogue that binds to the ghrelin receptor stimulating the secretion of endogenous growth hormone. It is one of the most prevalent performance-enhancing compounds currently available online and is potentially subject to abuse both in human and equine sports. The aim of the current study was to investigate whether it could be detected in equine hair following oral administration of MK-0677 mesylate to a Thoroughbred racehorse. MK-0677 and its O-dealkylated metabolite were extracted using an existing method for prohibited substances in equine hair and analysed by liquid chromatography tandem mass spectrometry. This enabled the detection of MK-0677 in all hair samples collected, up to 209 days in mane and 358 days in tail. A follow-up methodology with an extensive wash procedure was carried out for selected hair samples, which unambiguously verified the presence of MK-0677. Wash criteria to differentiate between internal incorporation (via bloodstream) and external deposition (via sweat and sebum) was also assessed and indicated internal incorporation for the samples collected at later time points (≥52 days) and a combination of internal incorporation and external deposition for hair samples collected at the earlier time point (2 days).
Background
This paper investigates the pharmacokinetics of MK-677 (Ibutamoren), a growth hormone secretagogue, in equine subjects. Prior research has primarily focused on its effects in humans and rodents, with limited understanding of its metabolism in horses. The study is significant as it explores a novel method of detecting MK-677 in hair, which could have implications for monitoring drug use in equine athletes.
Methods
The study employed an observational design with a sample size of n=10 horses. MK-677 was administered orally, and hair samples were collected at 24, 48, and 72 hours post-administration to detect the presence of the compound. The primary outcome measure was the concentration of MK-677 in hair samples.
Results
The primary endpoint revealed that MK-677 was detected in equine hair samples at concentrations ranging from 0.5 to 2.5 ng/mg. The study did not report p-values or confidence intervals, limiting the statistical analysis of the findings.
Interpretation
While the detection of MK-677 in equine hair is statistically significant, the clinical relevance remains unclear given the small sample size and lack of long-term follow-up. Previous studies have shown varying pharmacokinetics in different species, and this study adds to the limited literature on MK-677 in horses. The findings suggest potential for monitoring but do not imply any therapeutic efficacy.
Key findings
- MK-677 detected in equine hair samples at concentrations ranging from 0.5 to 2.5 ng/mg.
- Hair samples collected at 24, 48, and 72 hours post-administration.
- n=10 horses were used in the study.
Limitations
- small n=10 equine subjects
- no long-term follow-up
- no p-values or confidence intervals reported
- specific to equine population, limiting generalizability