Cardiopulmonary effects of clenbuterol in the horse.

The research article explores the effects of clenbuterol, a bronchospasmolytic (lung expansion) drug, on the heart and lung function in horses. The observations indicate that the drug significantly reduces the resistance in the lungs and causes a temporary increase in heart rate and decrease in arterial pressure.

Research Methodology

• The study involved the use of eight healthy horses. Four of these had instruments to measure intrapleural pressure and air flow for the purpose of calculating pulmonary resistance, peak flow rates, and tidal volumes. The remaining four were equipped to keep track of pulmonary arterial pressure, carotid arterial pressure, cardiac output, and arterial gas tensions.
• Measurements were taken before and after the administration of clenbuterol to observe changes in the test subjects’ physiological responses. The dosage used for the experiment was 0.8 micrograms per kilogram of body weight for each horse, injected intravenously.

Findings and Observations

• Clenbuterol was found to considerably reduce pulmonary resistance, with a 33.6% reduction being observed just 10 minutes after the drug’s administration. This reduced resistance level was maintained throughout the procedure, showing no sign of returning to pre-administration levels even three hours later.
• There was a marked decrease in carotid arterial pressure, averaging at a 28.2% decrease, within 30 seconds of the clenbuterol injection. This was accompanied by an almost doubling in heart rate.
• However, these changes were short-lived and they returned to their normal, control ranges within two minutes.

Conclusions and Recommendations

• Clenbuterol seems to be effective in reducing the non-elastic resistance of the lung in horses. This implies potential application of such beta 2 agonists in conditions where pulmonary resistance needs to be reduced.
• Despite the promising results, the authors caution against the intravenous administration of clenbuterol to animals with pre-existing cardiovascular or cardiopulmonary diseases, potentially due to recorded transient alterations in arterial pressure and heart rates.