Pharmacokinetics and disposition of clenbuterol in the horse.
Abstract: The pharmacokinetics of clenbuterol (CLB) following a single intravenous (i.v.) and oral (p.o.) administration twice daily for 7 days were investigated in thoroughbred horses. The plasma concentrations of CLB following i.v. administration declined mono-exponentially with a median elimination half-life (t(1/2k)) of 9.2 h, area under the time-concentration curve (AUC) of 12.4 ng.h/mL, and a zero-time concentration of 1.04 ng/mL. Volume of distribution (V(d)) was 1616.0 mL/kg and plasma clearance (Cl) was 120.0 mL/h/kg. The terminal portion of the plasma curve following multiple p.o. administrations also declined mono-exponentially with a median elimination half-life (t(1/2k)) of 12.9 h, a Cl of 94.0 mL/h/kg and V(d) of 1574.7 mL/kg. Following the last p.o. administration the baseline plasma concentration was 537.5 +/- 268.4 and increased to 1302.6 +/- 925.0 pg/mL at 0.25 h, and declined to 18.9 +/- 7.4 pg/mL at 96 h. CLB was still quantifiable in urine at 288 h following the last administration (210.0 +/- 110 pg/mL). The difference between plasma and urinary concentrations of CLB was 100-fold irrespective of the route of administration. This 100-fold urine/plasma difference should be considered when the presence of CLB in urine is reported by equine forensic laboratories.
Publication Date: 2004-04-21 PubMed ID: 15096103DOI: 10.1111/j.1365-2885.2004.00553.xGoogle Scholar: Lookup
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- Journal Article
- Research Support
- Non-U.S. Gov't
Summary
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This research article investigates the pharmacokinetics of a drug called clenbuterol in horses following both intravenous and oral administrations. This study helps define the most accurate way to test for the presence of this drug in racehorses.
Understanding the Study
- The focus of this study is clenbuterol, a drug commonly used in veterinary medicine. Researchers administered the drug to thoroughbred horses both intravenously and orally over a seven-day period to monitor how the drug distributes and leaves the body.
- Pharmacokinetics is a branch of pharmacology that focuses on how the body affects a specific drug after administration. It studies how the drug is absorbed, distributed, metabolized, and excreted from the body.
Key Findings
- The plasma concentration of clenbuterol after intravenous administration declined according to a mono-exponential model, with a half-life of 9.2 hours. The volume of distribution and plasma clearance were found to be relatively high, indicating that the drug spreads easily throughout the horse´s body and is eliminated rather quickly.
- After multiple oral administrations, the drug’s elimination half-life increased to 12.9 hours, indicating a slightly slower rate of elimination. The overall volume of distribution and plasma clearance reduced slightly compared to intravenous administration, suggesting that oral administration led to a slower distribution and elimination.
- The study also found that the concentrations of clenbuterol in urine were about 100 times higher than in plasma. This indicates that urine tests for clenbuterol usage in horses would yield more accurate results than blood tests.
Implications and Applications
- Understanding the pharmacokinetics of clenbuterol in horses is important for veterinarians who prescribe this drugs. Knowledge of how the drug distributes in the horse’s body and how long it stays in the system can help in adjusting the drug dosage for optimum effectiveness.
- The results of the study could also prove useful for regulatory bodies or investigators in horse racing who need to check for misuse of clenbuterol. The finding that clenbuterol concentrations in urine were about 100 times higher than in plasma suggests that urine tests could be more effective in detecting the drug.
Cite This Article
APA
Soma LR, Uboh CE, Guan F, Moate P, Luo Y, Teleis D, Li R, Birks EK, Rudy JA, Tsang DS.
(2004).
Pharmacokinetics and disposition of clenbuterol in the horse.
J Vet Pharmacol Ther, 27(2), 71-77.
https://doi.org/10.1111/j.1365-2885.2004.00553.x Publication
Researcher Affiliations
- School of Veterinary Medicine, University of Pennsylvania, New Bolton Center Campus, West Street Road, Kennett Square, PA 19348, USA. soma@mail.vet.upenn.edu
MeSH Terms
- Administration, Oral
- Animals
- Area Under Curve
- Bronchodilator Agents / administration & dosage
- Bronchodilator Agents / blood
- Bronchodilator Agents / pharmacokinetics
- Clenbuterol / administration & dosage
- Clenbuterol / blood
- Clenbuterol / pharmacokinetics
- Female
- Half-Life
- Horses
- Injections, Intravenous
- Intestinal Absorption
- Metabolic Clearance Rate
- Tissue Distribution
Citations
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