Pharmacokinetics of procaterol in thoroughbred horses.

The research article analyzes how procaterol (PCR), a drug used to treat respiratory disease in horses, is processed and eliminated from their bodies. The experiment administered the drug both orally and through intravenous injections and found that oral administration has poor bioavailability and the drug is eliminated slowly.

Introduction to Procaterol

• Procaterol (PCR) is a bronchodilator often used in treating lower respiratory diseases in racehorses, specifically in Japan.
• The purpose of this research was to investigate the pharmacokinetics, or how the horse’s body processes and eliminates the drug.

Study Methodology

• Researchers administered PCR to six thoroughbred horses, both intravenously (0.5 μg/kg) and orally (2.0 μg/kg).
• They then monitored the concentration of PCR in the horses’ plasma and urine, using liquid chromatography-mass spectrometry.

Key Findings

• The researchers found when PCR was administered intravenously, it followed a biphasic elimination pattern from the body. The rate of systemic clearance was 0.47 ± 0.16 L/h/kg, the steady-state volume of distribution was 1.21 ± 0.23 L/kg, and the elimination half-life was 2.85 ± 1.35 hours.
• They observed heart rate increase rapidly after intravenous administration and then decrease gradually. The researchers found a strong correlation between heart rate and plasma concentrations of PCR.
• They also found that when PCR was administered orally, plasma concentrations of the drug couldn’t be quantified at all, suggesting that oral bioavailability of PCR in horses is very poor.
• Urine concentrations of PCR could be quantified after both intravenous and oral administrations up to 32 hours after administration. There was no significant difference in concentrations after 24 hours between the two methods of drug administration.

Conclusion

• The study concludes that PCR, when orally administered, has poor bioavailability in horses, meaning the body could not effectively utilize the drug when administered orally. The drug is also eliminated more slowly, which was proven by the urinary concentrations of PCR.
• This research, being the first of its kind to showcase the pharmacokinetic character of PCR in thoroughbred horses, might impact future doses and administration method of this drug, potentially influencing racehorse health and performance.