Effectiveness of glyceryl trinitrate for enhancing digital submural perfusion in horses.

The research explores the efficacy of topical glyceryl trinitrate (GTN) in promoting blood flow in the lower parts of horse legs. The study found that GTN application did not significantly increase blood flow and rather decreased systemic pressure.

Study Objective and Method

• The study aims to assess how effective GTN is when administered topically to promote blood flow or vasodilation in the digital submural area of horses, a method proposed for preventing or treating laminitis, a painful and potentially debilitating hoof condition in horses.
• Seven adult horses with no foot abnormalities participated in the study. The chosen research design was concurrent-control crossover, intended for obtaining more reliable results by reducing possible confounding variables.
• The horse’s reactions to cold exposure, designed to induce digital vasoconstriction (constriction of blood vessels in horses’ feet), were gauged using instruments that detect wall surface temperature, mean systemic pressure (the pressure within the major circulatory system), and heart rate.
• Following cold exposure and vasoconstriction, GTN ointment was applied in an attempt to trigger digital vasodilation, or an increase in blood flow in the horse’s feet.

Research Findings

• The results did not showcase the desired outcome. Instead of increasing digital submural perfusion (blood flow), the application of GTN failed to bring about any noticeable increase.
• The study noted a mild decrease in mean systemic pressure following GTN application, signifying that the drug did get absorbed into the system.

Conclusion

• The research concluded that the topical application of GTN as a 2% ointment on the skin over the main vasculature near the proximal interphalangeal joint (pastern) of horses did not significantly enhance digital perfusion, contradicting its intended purpose.
• Usage of GTN could potentially result in a decrease in digital submural perfusion due to the induction of peripheral constriction or a decrease in the pressure needed for blood flow in the horse’s feet, which is the exact opposite of what is desired for laminitis prevention and treatment.