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Drug testing and analysis2021; 14(1); 39-55; doi: 10.1002/dta.3139

In vitro and in vivo metabolism of the anabolic-androgenic steroid oxandrolone in the horse.

Abstract: Oxandrolone is an anabolic-androgenic steroid with favourable anabolic to androgenic ratio, making it an effective anabolic agent with less androgenic side effects. Although its metabolism has been studied in humans, its phase I and II metabolism has not been previously reported in the horse. The purpose of this study was to investigate the in vitro metabolism of oxandrolone (using both equine liver microsomes and S9) and in vivo metabolism following oral administration (three daily doses of 50 mg of oxandrolone to a single Thoroughbred horse), using both gas and liquid chromatography-mass spectrometry techniques. The in vitro phase I transformations observed included 16-hydroxylated (two epimers), 17-methyl-hydroxylated and 16-keto metabolites. In addition to parent oxandrolone and these hydroxylated metabolites, the 17-epimer and a 17,17-dimethyl-18-norandrost-13-ene analogue were detected in biological samples following the administration. 16-keto-oxandrolone was only observed in urine. The 16- and 17-methyl-hydroxylated oxandrolone metabolites were predominantly excreted as sulfate conjugates in urine, whereas parent oxandrolone, its epimer and 17,17-dimethyl-18-norandrost-13-ene derivative were found predominantly in the unconjugated urine fraction. The most abundant analyte detected in both plasma and urine was parent oxandrolone. However, the longest detection period using the developed analytical method was provided by 17-hydroxymethyl-oxandrolone in both matrices. The results of this study provided knowledge of how best to detect the use of oxandrolone in regulatory samples.
© 2021 John Wiley & Sons, Ltd.
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Publication Date: 2021-08-26 PubMed ID: 34378336DOI: 10.1002/dta.3139Google Scholar: Lookup
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Summary

This research summary has been generated with artificial intelligence and may contain errors and omissions. Refer to the original study to confirm details provided. Submit correction.

This research study details the in vitro and in vivo metabolism of oxandrolone, an anabolic-androgenic steroid, in horses. The authors utilized both equine liver microsomes and extracted bodily samples, running tests aimed at a detailed observation of the metabolic processes, with special attention given to tracing and analyzing the different metabolites.

Objectives of the Research

  • The primary aim of the study was to shed light on the metabolic transformation of oxandrolone in horses, the understanding of which was limited at the time.
  • This was achieved through the careful analysis of both in vitro (lab-grown or synthetic instances of a horse’s liver microsystem) and in vivo (real horse) metabolic transformations after administering doses of oxandrolone.
  • The researchers hoped that their findings would provide a basis for more accurately detecting the use of oxandrolone in horse samples in future studies.

Methods and Techniques Used

  • The scientists used sophisticated gas and liquid chromatography-mass spectrometry techniques to monitor changes at the microscopic level and identify any metabolites produced.
  • Three daily doses of 50 mg of oxandrolone were given to a single Thoroughbred horse for the in vivo portion of the study.
  • The results were then compared with the outcomes of an in vitro experiment, using the horse’s liver microsystems.

Key Findings of the Research

  • The researchers observed that the in vitro phase I transformations of Oxandrolone resulted in a variety of metabolites, including 16-hydroxylated (two epimers), 17-methyl-hydroxylated, and 16-keto metabolites.
  • Following administration, parent oxandrolone and its hydroxylated metabolites, the 17-epimer, and a particular analog were detected in biological samples. However, 16-keto-oxandrolone was only observed in urine.
  • The 16- and 17-methyl-hydroxylated oxandrolone metabolites were predominantly excreted as sulfate conjugates in urine. In contrast, parent oxandrolone, its epimer, and the analogous metabolite were found predominantly in the unconjugated urine fraction.
  • Interestingly, the highest concentration of the steroid was found to be the parent oxandrolone in both plasma and urine.
  • Of the metabolites, the one offering the longest detection period was 17-hydroxymethyl-oxandrolone.

Implications of the Research

  • The findings of this study suggest new and potentially more efficacious methods for monitoring oxandrolone use among horses, especially for regulatory sampling purposes, given the understanding of the dominant metabolites and their respective concentrations in various body fluids.
  • This research provides a comprehensive report on oxandrolone metabolism in horses, filling a gap in the existing literature and paving the way for more precise and accurate detection procedures.

Cite This Article

APA
Harding C, Viljanto M, Cutler C, Habershon-Butcher J, Biddle S, Scarth J. (2021). In vitro and in vivo metabolism of the anabolic-androgenic steroid oxandrolone in the horse. Drug Test Anal, 14(1), 39-55. https://doi.org/10.1002/dta.3139

Publication

Drug testing and analysis
ISSN: 1942-7611
NlmUniqueID: 101483449
Country: England
Language: English
Volume: 14
Issue: 1
Pages: 39-55

Researcher Affiliations

Harding, Caitlin
  • Sports and Specialised Analytical Services, LGC, Fordham, Cambridgeshire, UK.
Viljanto, Marjaana
  • Sports and Specialised Analytical Services, LGC, Fordham, Cambridgeshire, UK.
Cutler, Charlotte
  • Sports and Specialised Analytical Services, LGC, Fordham, Cambridgeshire, UK.
Habershon-Butcher, Jocelyn
  • British Horseracing Authority, London, UK.
Biddle, Simon
  • Sports and Specialised Analytical Services, LGC, Fordham, Cambridgeshire, UK.
Scarth, James
  • Sports and Specialised Analytical Services, LGC, Fordham, Cambridgeshire, UK.

MeSH Terms

  • Anabolic Agents / analysis
  • Anabolic Agents / metabolism
  • Androgens / analysis
  • Androgens / metabolism
  • Animals
  • Chromatography, Liquid / methods
  • Chromatography, Liquid / veterinary
  • Doping in Sports / prevention & control
  • Gas Chromatography-Mass Spectrometry / methods
  • Gas Chromatography-Mass Spectrometry / veterinary
  • Horses
  • Male
  • Mass Spectrometry / methods
  • Mass Spectrometry / veterinary
  • Microsomes, Liver / metabolism
  • Oxandrolone / analysis
  • Oxandrolone / metabolism
  • Substance Abuse Detection / methods
  • Substance Abuse Detection / veterinary

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Citations

This article has been cited 1 times.
  1. Klöppner L, Harps LC, Parr MK. Sample Preparation Techniques for Growth-Promoting Agents in Various Mammalian Specimen Preceding MS-Analytics. Molecules 2024 Jan 9;29(2).
    doi: 10.3390/molecules29020330pubmed: 38257243google scholar: lookup
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