Control of methylxanthines in the competition horse: pharmacokinetic/pharmacodynamic studies on caffeine, theobromine and theophylline for the assessment of irrelevant concentrations.
Abstract: Methylxanthines positives in competition samples have challenged doping control laboratories and racing jurisdictions since methylxanthines are naturally occurring prohibited substances and often constituents of feed. For theobromine, an international threshold (renamed in International Residue Limit, IRL) of 2 µg/mL in urine has been established. On the basis of the data presented herein, a threshold or rather an IRL for theobromine in plasma of 0.3 µg/mL was proposed and was thereupon approved by the International Federation of Horseracing Authorities (IFHA). Official recommendations for reporting caffeine and theophylline are still lacking. The aim of the study was to investigate IRLs for theobromine in blood and for caffeine and theophylline in blood and urine. Therefore, a set of six administrations were carried out including both single i.v. and single oral administrations of caffeine, theobromine and theophylline. Plasma and urine concentrations were determined using a validated liquid chromatography-tandem mass spectrometry (LC-MS/MS). Applying the Toutain model approach an effective plasma concentration (EPC) of caffeine was estimated at 3.05 µg/mL, irrelevant concentrations in blood (IPC) and urine (IUC) approached 6 and 12 ng/mL, respectively. EPC of theobromine was calculated with 3.80 µg/mL, and irrelevant concentrations of theobromine were determined at 8 ng/mL in plasma and at 142 ng/mL in urine. Toutain modelling of the theophylline data produced an EPC, IPC, and IUC of 3.20 µg/mL, 6 ng/mL, and 75 ng/mL, respectively. The obtained irrelevant concentrations were used to postulate IRLs for theobromine in plasma and for caffeine and theophylline in plasma and urine. Copyright © 2016 John Wiley & Sons, Ltd.
Copyright © 2016 John Wiley & Sons, Ltd.
Publication Date: 2016-11-04 PubMed ID: 27662634DOI: 10.1002/dta.2097Google Scholar: Lookup
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- Journal Article
Summary
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This study focused on establishing irrelevant concentrations, or International Residue Limits (IRLs), for naturally occurring prohibited substances in competition horses – specifically caffeine, theobromine, and theophylline. Using a set of six different administrations of these substances and validating the outputs through liquid chromatography-tandem mass spectrometry, the study determined suggested IRLs for these substances in both plasma and urine.
Background of the Research
- Methylxanthines like caffeine, theobromine, and theophylline are naturally occurring substances that are often found in horse feed. However, they are considered prohibited in competition horses.
- Identifying an irrelevant concentration or IRL – a concentration level that doesn’t affect the horse’s performance – has been problematic. For theobromine, an IRL of 2 µg/mL in urine reportedly exists.
Objective and Methodology of the Study
- The study aimed to establish IRLs for theobromine in blood, and caffeine and theophylline both in blood and urine.
- Single Intravenous and oral administrations of these substances were carried out a total of six times.
- Plasma and urine concentrations were then determined using a validated liquid chromatography-tandem mass spectrometry (LC-MS/MS), a technique known for its sensitivity nand specificity.
Findings of the Study
- Applying the Toutain model, an estimation model used for this study, the effective plasma concentration (EPC) for caffeine was at 3.05 µg/mL, while the irrelevant concentrations in blood (IPC) and urine (IUC) were estimated at 6 and 12 ng/mL respectively.
- The EPC of theobromine was calculated at 3.80 µg/mL, with irrelevant concentrations estimated at 8 ng/mL in plasma and 142 ng/mL in urine.
- For theophylline, the EPC was at 3.20 µg/mL, and IPC and IUC were at 6 ng/mL and 75 ng/mL, respectively.
- These irrelevant concentrations determined in the study were used to suggest IRLs for these substances.
Importance and Impact of the Research
- This research paves the way for better doping control in the horseracing competition scene by establishing recommended IRLs for naturally occurring prohibited substances.
- It provides an empirical basis to detect the substance misuse and helps to ensure a fair, secure environment for competition.
Cite This Article
APA
Machnik M, Kaiser S, Koppe S, Kietzmann M, Schenk I, Düe M, Thevis M, Schänzer W, Toutain PL.
(2016).
Control of methylxanthines in the competition horse: pharmacokinetic/pharmacodynamic studies on caffeine, theobromine and theophylline for the assessment of irrelevant concentrations.
Drug Test Anal, 9(9), 1372-1384.
https://doi.org/10.1002/dta.2097 Publication
Researcher Affiliations
- Center for Preventive Doping Research - Institute of Biochemistry, German Sport University Cologne, Cologne, Germany.
- Department of Pharmacology, Toxicology and Pharmacy, University of Veterinary Medicine Hannover, Hannover, Germany.
- Department of Pharmacology, Toxicology and Pharmacy, University of Veterinary Medicine Hannover, Hannover, Germany.
- Department of Pharmacology, Toxicology and Pharmacy, University of Veterinary Medicine Hannover, Hannover, Germany.
- Center for Preventive Doping Research - Institute of Biochemistry, German Sport University Cologne, Cologne, Germany.
- German Equestrian Federation, Warendorf, Germany.
- Center for Preventive Doping Research - Institute of Biochemistry, German Sport University Cologne, Cologne, Germany.
- Center for Preventive Doping Research - Institute of Biochemistry, German Sport University Cologne, Cologne, Germany.
- Department of Experimental Physiopathology and Toxicology, National Veterinary School of Toulouse, Toulouse, France.
MeSH Terms
- Animals
- Caffeine / analysis
- Caffeine / chemistry
- Caffeine / pharmacokinetics
- Chromatography, Liquid / methods
- Horses
- Theobromine / analysis
- Theobromine / chemistry
- Theobromine / pharmacokinetics
- Theophylline / analysis
- Theophylline / chemistry
- Theophylline / pharmacokinetics
- Xanthines / chemistry
- Xanthines / pharmacokinetics
Citations
This article has been cited 4 times.- Eichler F, Poźniak B, Machnik M, Schenk I, Wingender A, Baudisch N, Thevis M, Bäumer W, Lischer C, Ehrle A. Pharmacokinetic modelling of orally administered cannabidiol and implications for medication control in horses. Front Vet Sci 2023;10:1234551.
- Marlier D. Doping in Racing Pigeons (Columba livia domestica): A Review and Actual Situation in Belgium, a Leading Country in This Field. Vet Sci 2022 Jan 22;9(2).
- Cui X, Lin Q, Liang Y. Plant-Derived Antioxidants Protect the Nervous System From Aging by Inhibiting Oxidative Stress. Front Aging Neurosci 2020;12:209.
- Roccaro M, Rinnovati R, Stucchi L, La Rocca F, Cascio G, Peli A. Survey on 9 years of anti-doping controls in horse races in Italy. Equine Vet J 2025 Nov;57(6):1592-1599.
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