Pharmacology of furosemide in the horse: a review.

The study reviews the pharmacological effects of furosemide, a diuretic drug, in horses. The drug is often used to prevent exercise-induced lung bleeding and for treating conditions like acute kidney failure and heart failure. Despite its common use, the study claims that definitive evidence of its efficacy in preventing lung bleeds associated with exercise or enhancing athletic performance is still lacking.

Pharmacology of Furosemide

• Furosemide is a diuretic drug extensively used in horses, especially those engaged in strenuous exercises. Its primary function is to increase the urinary excretion rate of sodium, chloride, and hydrogen ions. As a result, this reduces fluid retention in the body, thereby assisting in conditions like heart and kidney failures.
• The drug also affects plasma potassium concentration, which usually decreases post its administration. However, the impact on the urinary potassium excretion in horses is negligible.
• Furosemide is also known to increase renal blood flow. This effect indicates that the drug has direct influences on the functioning of the kidneys.

Systemic and Renal Hemodynamic Effects

• Furosemide impacts the overall hemodynamics of the body system. It brings about an increase in venous compliance and a decrease in right atrial pressure, pulmonary artery pressure, pulmonary artery wedge pressure, and pulmonary blood volume.
• The systemic effects of furosemide, however, only become apparent when the kidneys are fully functional. These impacts can occur even when the body does not produce urine, which underscores the significance of furosemide’s extra-renal effects, which depend on functional kidneys.
• The renal and systemic effects of furosemide can be modified if the horse has been previously treated with nonsteroidal anti-inflammatory drugs.

Furosemide’s Efficacy

• Furosemide’s utility extends to mitigating exercise-induced increases in various pressure parameters inside horses, like right atrial, aortic, and pulmonary artery pressures.
• In human subjects, furosemide is effective in preventing bronchoconstriction (narrowing of airways in the lungs) triggered by exercise and allergens. Additionally, it can decrease the total pulmonary resistance in ponies afflicted with recurrent obstructive airway disease.
• However, despite the commonly perceived benefits, the research indicates that conclusive evidence is still missing on furosemide’s actual efficacy in preventing exercise-induced lung bleeds or enhancing athletic performance in horses. Thus, more rigorous studies might be required before making a final judgment about its application.