Effect of phenylbutazone on the haemodynamic, acid-base and eicosanoid responses of horses to sustained submaximal exertion.

This research investigates the effects of phenylbutazone on the cardiovascular and acid-base systems of horses during rest and sustained submaximal exercise. It reveals that phenylbutazone can inhibit the exercise-induced increase in certain blood components but does not have a noticeable impact on the horse’s systemic haemodynamics or acid-base responses.

Study Setup

• The research was conducted on six mares, each of which was administered phenylbutazone (a nonsteroidal anti-inflammatory drug) or a placebo. The drug was administered either 15 minutes before or 30 minutes into a 60-minute submaximal exercise test.
• The exercise test was designed to elicit heart rates approximately 55% of the horse’s maximum. The same protocol was applied to the horses at rest as a control.

Measured Variables

• Various variables such as cardiac output, heart rate, systemic and pulmonary arterial pressures, right atrial and right ventricular pressures, and arterial and mixed venous blood gases, and pH were examined to understand the systemic haemodynamic effects.
• Researchers also studied the concentration of serum sodium, potassium, chloride, and plasma thromboxane B2, 6-keto-prostaglandin F1 alpha (6-keto-PGF1 alpha), and prostaglandin E2 (PGE2) in the blood.

Findings

• The exercise resulted in increased heart rate, cardiac output, mean arterial and right ventricular pressure, while decreasing total peripheral resistance. Furthermore, the horses exhibited respiratory alkalosis as the acid-base response to the exertion.
• In terms of eicosanoid (a type of lipid) responses, the exertion didn’t significantly alter the concentrations of 6-keto-PGF1 alpha or PGE2. However, there was a significant increase in plasma thromboxane B2 concentration post-exercise in untreated horses.
• Interestingly, the administration of phenylbutazone inhibited this exercise-induced increase in plasma thromboxane B2. Nevertheless, phenylbutazone had no detectable effects on the systemic haemodynamic or acid-base variables, regardless of whether the horses were standing or running.

Implications

The study reveals the potential of Phenylbutazone to alter certain blood components related to inflammation and platelet aggregation in the body of horses. However, it does not seem to affect the major cardiovascular and acid-base parameters, rendering it potentially safe and beneficial, particularly in horses engaged in physical exertion. More in-depth studies might be needed to understand its therapeutic potential fully.