An interlaboratory study of the pharmacokinetics of testosterone following intramuscular administration to Thoroughbred horses.
Abstract: Testosterone is an anabolic androgenic steroid (AAS) that is endogenously produced by both male and female horses that also has the potential for abuse when administered exogenously to race horses. To recommend appropriate withdrawal guidelines so that veterinarians can discontinue therapeutic use prior to competition, the pharmacokinetics and elimination of testosterone were investigated. An aqueous testosterone suspension was administered intramuscularly in the neck of Thoroughbred horses (n = 20). The disposition of testosterone from this formulation was characterized by an initial, rapid absorption phase followed by a much more variable secondary absorption phase. The median terminal half-life was 39 h. A second focus of this study was to compare the testosterone concentrations determined by two different laboratories using a percentage similarity model with a coefficient of variation of 16.5% showing good agreement between the two laboratories results. Based on the results of this study, a withdrawal period of 30 days for aqueous testosterone administered IM is recommended.
© 2011 Blackwell Publishing Ltd.
Publication Date: 2011-03-02 PubMed ID: 21366623DOI: 10.1111/j.1365-2885.2011.01277.xGoogle Scholar: Lookup
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- Journal Article
Summary
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The research is focused on studying how testosterone, a steroid, is absorbed and eliminated from racehorses bodies after it’s injected. Findings suggest a safe withdrawal period of 30 days before competition for horses to ensure there are no hormones left in systems that could give them an artificial edge during racing.
Research Purpose
- The paper aims to evaluate the pharmacokinetics (the study of how drugs move within the body) and elimination of testosterone in Thoroughbred racehorses after it is administered to them.
- Testosterone, an anabolic androgenic steroid, is naturally produced by both male and female horses but can be artificially injected to enhance the horse’s performance. This study aims at recommending suitable withdrawal periods for such horses so they can compete fairly in races.
Methodology
- The researchers injected an aqueous testosterone suspension into the necks of 20 Thoroughbred horses.
- The team observed how this formulation was absorbed into the horses’ bodies, with the absorption process having an initial fast phase that was followed by a more variable secondary phase.
- A secondary target of the study was the comparison of testosterone concentrations as evaluated by two different laboratories. They used a percentage similarity model for this comparison.
Findings
- The median terminal half-life of the testosterone was found to be 39 hours. Half-life refers to the time it takes for the concentration of a substance to decrease by half in the body.
- The results from the two different laboratories were similar with a coefficient of variation of 16.5%, showing good agreement between them.
Recommendations
- Based on these findings, the authors suggest a withdrawal period of 30 days for horses who have received an intramuscular administration of aqueous testosterone. This recommendation is made in order to ensure the raced horses are not benefiting from any exogenous testosterone advantage.
Cite This Article
APA
Moeller BC, Sams RA, Guinjab-Cagmat J, Szabo NJ, Colahan P, Stanley SD.
(2011).
An interlaboratory study of the pharmacokinetics of testosterone following intramuscular administration to Thoroughbred horses.
J Vet Pharmacol Ther, 34(6), 588-593.
https://doi.org/10.1111/j.1365-2885.2011.01277.x Publication
Researcher Affiliations
- K.L. Maddy Equine Analytical Chemistry Laboratory, California Animal Health and Food Safety Laboratory, School of Veterinary Medicine, University of California at Davis, USA.
MeSH Terms
- Androgens / administration & dosage
- Androgens / blood
- Androgens / pharmacokinetics
- Animals
- Chromatography, High Pressure Liquid / veterinary
- Female
- Half-Life
- Horses / blood
- Injections, Intramuscular / veterinary
- Male
- Reproducibility of Results
- Tandem Mass Spectrometry / veterinary
- Testosterone / administration & dosage
- Testosterone / blood
- Testosterone / pharmacokinetics
Citations
This article has been cited 1 times.- Bi Y, Perry PJ, Ellerby M, Murry DJ. Population Pharmacokinetic/Pharmacodynamic Modeling of Depot Testosterone Cypionate in Healthy Male Subjects. CPT Pharmacometrics Syst Pharmacol 2018 Apr;7(4):259-268.
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