Studies of meclofenamic acid and two metabolites in horses–pharmacokinetics and effects on exercise tolerance.

The research investigates the pharmacokinetics of the anti-inflammatory drug meclofenamic acid in Seven Standardbred horses and its impact on their treadmill exercise performance. The decline in plasma concentration, absorption rate, and effects on exercise tolerance were analyzed.

Study Design and Process

• The study involved seven Standardbred horses. The anti-inflammatory drug meclofenamic acid was administered to the horses through either a single intravenous dose or oral doses. The study intended to evaluate the pharmacokinetics, i.e., how the drug moves within the horse’s body and how the drug affects the horse’s exercise ability.
• Post a single intravenous dose of meclofenamic acid; the plasma concentration declines were described using a two-compartment open model. The researchers used this to calculate the average elimination half-life, apparent volume of distribution, and plasma clearance.
• The researchers also analyzed the pharmacokinetics of two metabolites of meclofenamic acid from two horses, comparing their elimination half-lives.

Results and Findings

• The study found that the absorption of the drug was the rate-limiting step post its oral administration. A non-compartmental analysis showed a mean absorption time of 4.3 h.
• The average elimination half-life, which is the time it takes for the drug’s concentration in the body to reduce by half, was 1.4 hours. The apparent volume of distribution was 0.14 l/kg, and the plasma clearance was 0.12 l/h kg.
• The elimination half-lives of the two metabolites were found to be virtually identical in each horse, being 3.0 hours and 3.4 hours respectively.
• The research also studied the impact of this drug on the horses’ exercise regime. The blood lactate response to exercise was significantly reduced post meclofenamic acid treatment, indicating a reduced utilization of the glycolytic, anaerobic, energy contribution during exercise. Meaning the medication potentially decreases the need for the anaerobic process that occurs during intense physical exercise.
• There was no apparent effect on the circulatory capacity of the horses after the medication, with the heart rate response remaining unchanged during exercise.