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Drug testing and analysis2025; doi: 10.1002/dta.3885

In Vivo Metabolic Studies of 2-Hydroxyethyl Salicylate in Horses.

Abstract: 2-Hydroxyethyl salicylate (2HES), a nonsteroidal anti-inflammatory drug (NSAID), is a medication to treat musculoskeletal injuries and inflammation swelling of humans and horses. Its misuse could affect the performance of horses and mask injuries, which could pose significant health risks. In horseracing, it is reported as an adverse finding once detected in competition. The metabolism of 2HES in either human or horse has not been reported, and therefore, little is known about its metabolic fate. This paper describes the in vivo metabolism of 2HES in horse with an objective to identify the most appropriate target(s) for detecting 2HES administration. To study the elimination and biotransformation of 2HES, topical administrations were performed by giving three castrated horses (geldings) each a total of 100-g Tensolvet gel (equivalent to 5 g of 2HES). The postulated in vivo metabolites included glucuronide-conjugated 2HES (2HES-Glu) and sulphate-conjugated 2HES (2HES-SO) from Phase II conjugation possibly at hydroxyethyl moiety and salicylic acid (SA) from hydrolysis of 2HES. To control the misuse of 2HES in horses effectively, 2HES was found to be the most suitable target. Total 2HES could be detected for up to 10 days in urine, whereas free 2HES could be detected for 16 h in plasma. As the maximum concentration of SA in postadministration urine and plasma sample did not exceed its corresponding international thresholds, monitoring the amount of SA could not be used as an indicator for possible 2HES exposure.
© 2025 John Wiley & Sons Ltd.
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Publication Date: 2025-03-12 PubMed ID: 40075191DOI: 10.1002/dta.3885Google 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 article details an investigative study into the metabolism and elimination of 2-Hydroxyethyl Salicylate (2HES), a nonsteroidal anti-inflammatory drug, in horses to identify suitable targets for detecting its administration.

Objectives of the Study

  • The study aims to analyse the metabolism of 2-Hydroxyethyl Salicylate (2HES) in horses to allow for efficient detection of its administration.
  • As 2HES can potentially improve a horse’s performance or mask injuries, understanding its metabolic process can help ensure the integrity of horse racing and safeguard the wellbeing of horses.

Methodology

  • To investigate the in vivo metabolism of 2HES, a topical application of a gel equivalent to 5g of 2HES was administered to three geldings (castrated horses).
  • The researchers theorised potential in vivo metabolites including glucuronide-conjugated 2HES, sulphate-conjugated 2HES, and salicylic acid resulting from the hydrolysis of 2HES.
  • They expected these metabolites to be prominent in the Phase II conjugation and hydroxyethyl moiety.

Findings

  • The researchers discovered that to control the misuse of 2HES in horses effectively, monitoring the presence of 2HES is the most suitable method.
  • They noted that total 2HES could be detected for up to 10 days in urine, whereas free 2HES could be detected for 16 hours in plasma.
  • Finally, they found that the level of salicylic acid in post-administration urine and plasma samples did not exceed the corresponding international thresholds. Hence, the quantity of salicylic acid cannot be used as an indication for possible 2HES exposure.

In conclusion, this study provides valuable insights into the metabolism of 2HES in horses. This information can guide more effective methods to detect its administration, maintain the integrity of horse races, and protect the health of horses.

Cite This Article

APA
Ho HSM, Farrington AF, Ho ENM, Wong WT. (2025). In Vivo Metabolic Studies of 2-Hydroxyethyl Salicylate in Horses. Drug Test Anal. https://doi.org/10.1002/dta.3885

Publication

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

Researcher Affiliations

Ho, Helen S M
  • Department of Applied Biology and Chemical Technology, Hong Kong Polytechnic University, Kowloon, Hong Kong Special Administrative Region, China.
Farrington, Adrian F
  • Department of Veterinary Clinical Services, Hong Kong Jockey Club, Sha Tin, Hong Kong Special Administrative Region, China.
Ho, Emmie N M
  • Racing Laboratory, Hong Kong Jockey Club, Sha tin Racecourse, Sha Tin, Hong Kong Special Administrative Region, China.
Wong, Wing-Tak
  • Department of Applied Biology and Chemical Technology, Hong Kong Polytechnic University, Kowloon, Hong Kong Special Administrative Region, China.

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