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Drug testing and analysis2025; doi: 10.1002/dta.3919

Metabolic Studies of Nandrolone Decanoate in Castrated Horses After Intramuscular Administration.

Abstract: This paper describes the studies of the in vitro biotransformation of nandrolone decanoate and its metabolic fate in equine plasma and urine after intramuscular administration to castrated thoroughbred horses. The in vitro metabolic study was performed using homogenised horse liver, and the more prominent in vitro biotransformation pathways were found to include hydrolysis, reduction, oxidation and sulfation, mainly resulting in seven Phase I metabolites and one Phase II metabolite. The administration study of nandrolone decanoate was carried out using three retired thoroughbred geldings, each of which was administered intramuscularly with 800 mg of nandrolone decanoate (Deca-Durabolin) once weekly for three consecutive weeks. Nandrolone decanoate and the majority of the identified in vitro metabolites were detectable in post-administration plasma samples for at least 20 days (last sample collected) after the last administration. Although nandrolone decanoate was not found in any post-administration urine, nandrolone (as a metabolite) and its downstream metabolites can be detected for at least 20 days post-administration (last sample collected). For doping control purpose, nandrolone decanoate itself could be a suitable target analyte in horse plasma for effectively controlling its misuse in equine sports.
© 2025 John Wiley & Sons Ltd.
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Publication Date: 2025-07-01 PubMed ID: 40589378DOI: 10.1002/dta.3919Google 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.

The research paper focuses on the metabolic study of nandrolone decanoate, a steroid, in castrated horses and its possible misuse in equine sports. The drug was introduced into the horses through intramuscular administration and the metabolic pathway along with the resultant metabolites were studied. The authors suggest nandrolone decanoate could serve as a suitable target for doping control in equine sports.

Metabolic Study In Vitro

  • The first part of the research was dedicated to the in vitro biotransformation of nandrolone decanoate. This transformation was observed using a homogenised horse liver to replicate the possible reactions within the horse’s body.
  • The transformation process included hydrolysis, reduction, oxidation and sulfation. These processes resulted in seven major Phase I metabolites and one Phase II metabolite.

Administration Study of Nandrolone Decanoate

  • The researchers administered three retired thoroughbred geldings, each with 800 mg of nandrolone decanoate (Deca-Durabolin) via intramuscular injection. The administration happened once a week for three consecutive weeks.
  • The goal of this part of the study was to track the presence of nandrolone decanoate and its metabolites in the horse’s plasma and urine after administration of the drug.

Presence and Detection of Nandrolone Decanoate

  • Nandrolone decanoate and most of the identified in vitro metabolites were found to be detectable in post-administration plasma samples for at least 20 days after the final administration.
  • Notably, while nandrolone decanoate itself was not detected in post-administration urine, nandrolone (as a metabolite) and its downstream metabolites were detectable in the urine for a similar duration of 20 days post-administration.

Implications for Doping Control

  • The research suggests that nandrolone decanoate can act as a significant target analyte for doping control in equine sports.
  • Its presence in horse plasma and its measurable duration aid in making it a reliable indicator of potential misuse of the steroid in the sport.

Cite This Article

APA
So YM, Kwok WH, Tang CWY, Wong COL, Wan TSM, Ho ENM. (2025). Metabolic Studies of Nandrolone Decanoate in Castrated Horses After Intramuscular Administration. Drug Test Anal. https://doi.org/10.1002/dta.3919

Publication

Drug testing and analysis
ISSN: 1942-7611
NlmUniqueID: 101483449
Country: England
Language: English

Researcher Affiliations

So, Yat-Ming
  • Racing Laboratory, The Hong Kong Jockey Club, Sha Tin Racecourse, Sha Tin, New Territories, Hong Kong, China.
Kwok, Wai Him
  • Racing Laboratory, The Hong Kong Jockey Club, Sha Tin Racecourse, Sha Tin, New Territories, Hong Kong, China.
Tang, Christina W Y
  • Racing Laboratory, The Hong Kong Jockey Club, Sha Tin Racecourse, Sha Tin, New Territories, Hong Kong, China.
Wong, Celia O L
  • Racing Laboratory, The Hong Kong Jockey Club, Sha Tin Racecourse, Sha Tin, New Territories, Hong Kong, China.
Wan, Terence S M
  • Racing Laboratory, The Hong Kong Jockey Club, Sha Tin Racecourse, Sha Tin, New Territories, Hong Kong, China.
Ho, Emmie N M
  • Racing Laboratory, The Hong Kong Jockey Club, Sha Tin Racecourse, Sha Tin, New Territories, Hong Kong, China.

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