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Drug metabolism in the horse: a review.
Abstract: A detailed understanding of equine drug metabolism is important for detection of drug abuse in horseracing and also in veterinary drug development and practice. To date, however, no comprehensive review of equine drug metabolism has been published. The majority of literature regarding equine drug metabolite profiles is derived from sports drug detection research and is generally targeted at detecting marker metabolites of drug abuse. However, the bulk of the literature on equine drug metabolism enzymology is derived from veterinary studies aimed at determining the molecular basis of metabolism. In this article, the phase 1 and 2 metabolisms of seven of the most important classes of drugs monitored in horseracing are reviewed, including: anabolic-androgenic steroids (AAS), β₂ -agonists, stimulants, sedatives/tranquilizers, local anesthetics, non-steroidal anti-inflammatory analgesics (NSAIDS)/cyclooxygenase-2 (COX-2) inhibitors, and opioid analgesics. A summary of the literature relating to the enzymology of drug metabolism in this species is also be presented. The future of equine drug metabolism in the area of doping research will be influenced by several factors, including: a possible move towards the increased use of blood and other alternative testing matrices; the development of assays based on intact drug conjugates; the increasing threat of 'designer' and herbal- based products; advances in the use of in vitro technologies; the increased use of liquid-chromatography/high-resolution mass spectrometry; and the possibility of screening using 'omics' approaches. Also, the recent cloning of a range of equine cytochrome P450 (CYP) enzymes opens up the potential for carrying out more detailed mechanistic pharmacological and toxicological veterinary studies.
Copyright © 2010 John Wiley & Sons, Ltd.
Publication Date: 2010-10-22 PubMed ID: 20967889DOI: 10.1002/dta.174Google Scholar: Lookup The Equine Research Bank provides access to a large database of publicly available scientific literature. Inclusion in the Research Bank does not imply endorsement of study methods or findings by Mad Barn.
- Journal Article
- Research Support
- Non-U.S. Gov't
- Review
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 provides a comprehensive review of the metabolism of drugs in horses, focusing on seven key types of drugs widely monitored in horse racing. Additionally, it outlines the future direction of detecting drug abuse in horses, taking into account new technologies and methodologies.
Background
- The article begins by emphasizing the significance of understanding equine drug metabolism for two primary reasons: detecting drug misuse in horse racing and aiding in the veterinary practice and development of drugs.
- The article indicates that sufficient literature has not been previously compiled on this topic, with most available research focusing on identifying drug abuse indicators in sports and exploring the molecular basis of metabolism in vet studies.
Classes of Drugs Studied
- The research analyzes the metabolism of seven widely monitored classes of drugs in horse racing: anabolic-androgenic steroids (AAS), β₂ -agonists, stimulants, sedatives/tranquilizers, local anesthetics, non-steroidal anti-inflammatory analgesics (NSAIDS)/cyclooxygenase-2 (COX-2) inhibitors, and opioid analgesics.
- It delves into detailing the phase 1 and 2 metabolisms of these drug classes, offering an insight into their biological transformation process in the horse body. Phase 1 metabolism typically involves chemical modification of the drugs, while phase 2 metabolism usually includes a conjugation reaction, which enhances the drug’s solubility, promoting its elimination from the body.
Future of Equine Drug Metabolism
- The research article also presents a forward-looking view on the future of studying drug metabolism in horses, outlining influencing factors like the potential increase in use of blood and other alternative testing matrices, the development of assays based on intact drug conjugates, and the emerging threat from ‘designer’ and herbal-based products.
- Proponents for the adoption of new technologies like liquid-chromatography/high-resolution mass spectrometry and the potential application of ‘omics’ approaches in screening are also highlighted.
- The cloning of various equine cytochrome P450 (CYP) enzymes has unlocked potential for conducting in-depth mechanistic pharmacological and toxicological veterinary examinations.
Cite This Article
APA
Scarth JP, Teale P, Kuuranne T.
(2010).
Drug metabolism in the horse: a review.
Drug Test Anal, 3(1), 19-53.
https://doi.org/10.1002/dta.174 Publication
Researcher Affiliations
- A Quotient Bioresearch Ltd Company, Fordham, Cambridgeshire, UK. jscarth@hfl.co.uk
MeSH Terms
- Animals
- Biotransformation
- Doping in Sports
- Horses / metabolism
- Performance-Enhancing Substances / analysis
- Performance-Enhancing Substances / pharmacokinetics
- Reproducibility of Results
- Species Specificity
- Substance Abuse Detection / veterinary
Citations
This article has been cited 9 times.- Serrano-Rodríguez JM, Miraz R, Saitua A, Díez de Castro E, Ledesma-Escobar C, Ferreiro-Vera C, Priego-Capote F, Sánchez de Medina V, Sánchez de Medina A. Metabolism, pharmacokinetics, and bioavailability of cannabigerol in horses following intravenous and oral administration with micellar and oil formulations. Front Vet Sci 2025;12:1688214.
- Karačonji IB, Jelača T, Jurič A, Vrdoljak AL. Morphine and codeine in racing horse feed: is there reason for concern?. Arh Hig Rada Toksikol 2025 Mar 1;76(1):60-66.
- Elbourne M, Keledjian J, Cawley A, Fu S. Administration Route Differentiation of Altrenogest via the Metabolomic LC-HRMS Analysis of Equine Urine. Molecules 2024 Oct 22;29(21).
- Garcia Filho SG, de Andrade FSRM, Dos Santos RST, Gonçalves LA, Pereira MAA, de Souza AF, Ambrósio AM, Fantoni DT. Comparison of Hemodynamic Effects of Dobutamine and Ephedrine Infusions in Isoflurane-Anesthetized Horses. Vet Sci 2023 Apr 6;10(4).
- Kośka I, Kubalczyk P. Development of the Chromatographic Method for Simultaneous Determination of Azaperone and Azaperol in Animal Kidneys and Livers. Int J Mol Sci 2022 Dec 21;24(1).
- Fitzgerald CCJ, Hedman R, Uduwela DR, Paszerbovics B, Carroll AJ, Neeman T, Cawley A, Brooker L, McLeod MD. Profiling Urinary Sulfate Metabolites With Mass Spectrometry. Front Mol Biosci 2022;9:829511.
- Tozaki T, Ohnuma A, Kikuchi M, Ishige T, Kakoi H, Hirota KI, Kusano K, Nagata SI. Rare and common variant discovery by whole-genome sequencing of 101 Thoroughbred racehorses. Sci Rep 2021 Aug 6;11(1):16057.
- Rosa B. Equine Drug Transporters: A Mini-Review and Veterinary Perspective. Pharmaceutics 2020 Nov 8;12(11).
- Tydén E, Tjälve H, Larsson P. Gene and protein expression and cellular localisation of cytochrome P450 enzymes of the 1A, 2A, 2C, 2D and 2E subfamilies in equine intestine and liver. Acta Vet Scand 2014 Oct 8;56(1):69.
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