The equine metabolism of the catechol-O-methyltransferase enzyme inhibitor nitecapone.
Abstract: The abuse of performance-enhancing catecholamine-based stimulants, such as levodopa, is controlled in horse racing through the application of a regulatory threshold for the common major metabolite. However, catechol-O-methyltransferase (COMT) enzyme inhibitors can be used to restrict the catalysis of the stimulant, and so the concurrent administration of both substances would be a viable strategy to enhance racing performance while removing the risk of exceeding the threshold. A 200 mg dose of nitecapone, a COMT inhibitor, was administered to a Thoroughbred horse, and we have analysed the blood (≤24 h) and urine (≤48 h) samples that were collected. The extracts, analysed by UHPLC coupled to a high-resolution accurate mass spectrometer, were consistent with the presence of nitecapone glucuronide in all the samples collected. An in-depth examination of the samples was then carried out using targeted accurate mass extracted ion chromatograms to identify whether the metabolites that have been found in other species were also present in the extracts. Once these were tentatively identified, MS/MS experiments were conducted on some of the metabolites (M1-M5), as well as decomposition products (DP1 and DP2), to verify that spectrum included MS fragments were consistent with their proposed structures. The accumulated data provided evidence that is consistent with this drug having been converted into many metabolites and a few decomposition products. An unexpected finding was that O-methylation was a very minor pathway until after the reduction of the 2,4-pentanedione side chain had occurred.
© 2021 John Wiley & Sons, Ltd.
Publication Date: 2021-10-18 PubMed ID: 34545698DOI: 10.1002/dta.3163Google Scholar: Lookup
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Summary
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The research investigates how the horse’s body metabolizes the drug nitecapone – a substance that can enhance racing performance by restricting the breakdown of stimulants that boost activity.
Overview of the Research
The researchers administered a 200mg dose of nitecapone to a Thoroughbred horse, then collected and analyzed the horse’s blood and urine samples for up to 24 and 48 hours respectively using UHPLC coupled to a high-resolution accurate mass spectrometer. The aim of the study was to understand how nitecapone is metabolised in the horse’s body, particularly since it’s an inhibitor of the enzyme COMT that breaks down performance-boosting catecholamine-based stimulants in horse racing.
Analysis and Results
- The findings confirmed the presence of nitecapone glucuronide in all the samples collected, suggesting that the administered drug was indeed metabolized and excreted in the horse’s body.
- Using targeted accurate mass extracted ion chromatograms, in-depth examination of the samples was done to identify if the metabolites found in other species were also present in the extracts from the horse.
- Metabolites (M1-M5), as well as decomposition products (DP1 and DP2), were then subjected to MS/MS experiments to verify their proposed structures. This helped the researchers confirm the specific metabolites and decomposition products resulting from the nitecapone metabolism in horse.
- The analysis yielded an unexpected finding – O-methylation, a metabolic pathway, was observed to a significantly less extent until after the reduction of the 2,4-pentanedione side chain. This suggests unique metabolic processes of nitecapone specific to horse.
Implications
The study provides a thorough understanding of how the drug Nitecapone is metabolized in horses. Knowing how a horse’s body processes such a substance can help regulate the use or abuse of performance-enhancing drugs in horse racing. This contributes to a fairer and more controlled athletic environment, while also attending to the wellbeing of the animals involved.
Cite This Article
APA
Stanley S, Deng D, Van den Berg K, Foo HC.
(2021).
The equine metabolism of the catechol-O-methyltransferase enzyme inhibitor nitecapone.
Drug Test Anal, 14(5), 929-935.
https://doi.org/10.1002/dta.3163 Publication
Researcher Affiliations
- Racing Science Centre, Queensland Racing Integrity Commission, Brisbane, Australia.
- Singapore Turf Club, Singapore, Singapore.
- Singapore Turf Club, Singapore, Singapore.
- Singapore Turf Club, Singapore, Singapore.
- Singapore Turf Club, Singapore, Singapore.
MeSH Terms
- Animals
- Catechol O-Methyltransferase / metabolism
- Catechol O-Methyltransferase Inhibitors
- Catechols
- Horses
- Pentanones
- Tandem Mass Spectrometry
References
This article includes 14 references
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