Attenuation by phenylbutazone of the renal effects and excretion of frusemide in horses.

This study investigated how pre-treatment with phenylbutazone, an anti-inflammatory drug, impacts the distribution and removal of frusemide, a diuretic medication, in horses. The results showed that phenylbutazone reduces the excretion of frusemide and the increase it causes in urinary sodium and chloride, but it does not affect frusemide’s intrarenal activity.

Objectives and Methodology

• The researchers aimed to determine the impact of premedication with phenylbutazone on the pharmacokinetics (how a drug is absorbed, distributed, metabolized, and excreted) and urinary excretion of frusemide in horses.
• They also wanted to assess phenylbutazone’s effect on the changes in urinary electrolyte (like sodium, potassium, and chloride) excretion brought on by frusemide.
• Using six Standardbred mares in a 3-way crossover design, the team studied the pharmacokinetics and renal effects of frusemide with and without phenylbutazone premedication. They also had a control group that received a saline treatment.

Findings and Conclusion

• The administration of frusemide without phenylbutazone resulted in diuresis (increased urine production), natriuresis (excess sodium in urine), kaliuresis (excess potassium in urine), and chloruresis (excess chloride in urine), and changed the ratio of sodium:chloride excretion from 0.4 to 1.0 in the first hour of diuresis.
• When frusemide and phenylbutazone were given together, sodium and chloride excretion in the first hour decreased significantly compared to the administration of frusemide without phenylbutazone.
• The clearance of sodium and chloride was also notably reduced with the combination of phenylbutazone and frusemide. However, potassium excretion, potassium clearance, and the ratio of sodium to chloride excretion remained unaffected.
• Phenylbutazone did not influence frusemide’s efficiency regarding electrolyte excretion during peak diuresis, nor did it impact the plasma disposition of frusemide. However, it reduced the renal excretion of frusemide by about 25%.
• In conclusion, the researchers state that the diminished urinary excretion of frusemide due to phenylbutazone results in a decreased rise in urinary sodium and chloride excretion. However, phenylbutazone does not inhibit the intrarenal activity of frusemide in horses.