Effects of clenbuterol hydrochloride on certain respiratory and cardiovascular parameters in horses performing treadmill exercise.

This study investigated how using the drug clenbuterol hydrochloride affects respiratory and cardiovascular responses in horses during and after exercise. The researchers found that while the drug caused some temporary changes in heart rate and blood gases, it did not have any detrimental effects on the horses’ circulatory systems.

Study Methodology

• The study involved five standardbred geldings (a breed of horse). These horses were given intravenous injections of clenbuterol hydrochloride and saline in a crossover experiment.
• The horses performed a four-step treadmill exercise at varying speeds, with each step lasting for two minutes, apart from step four which lasted four minutes.
• Before exercise, and at various points during and after the exercise, the researchers collected data on various cardiorespiratory parameters. These included arterial and mixed venous blood gases, mean arterial pressure, mean pulmonary artery pressure, electrocardiogram, and respiratory rate.

Findings

• After receiving clenbuterol, the horses experienced a brief drop in mean arterial pressure which returned to normal levels after 90 seconds.
• There was no observed change in mean pulmonary artery pressure.
• During exercise, the heart rate of the horses was significantly higher at the end of certain stages, and after 10 minutes of recovery. This was apparent when comparing the results of horses given clenbuterol and those given saline.
• There were no noticeable negative effects on the horses’ electrocardiograms (the record of electrical activity in the heart).
• The results showed that clenbuterol caused an increase in arterial oxygen tension (PaO2) and a decrease in arterial carbon dioxide pressure (PaCO2) one minute after exercise, compared to the saline group.

Conclusion

• The study concluded that there was no evidence of significant negative effects of clenbuterol on the circulatory system of horses during exercise. While the drug did cause some changes in cardiorespiratory parameters, these were transient and did not indicate detrimental health effects.