Urinary and serum concentrations of diclofenac after topical application to horses.

The study investigates the concentrations of diclofenac, a common anti-inflammatory drug, in horse urine and blood serum following the topical application of its liposomal cream formulation for 10 days at various dosages. The results provide insight into the correct withdrawal period needed before a horse racing event to avoid positive drug test results.

Objective and Methodology of the Study

• The primary aim of the study was to determine the presence of diclofenac in the urinary and serum concentrations in horses after its topical application. The subject drug used was the 1% liposomal diclofenac cream, specifically designed for localized areas of inflammation in horses.
• The diclofenac was applied for 10 days, with different experimental groups receiving different dosages – the labeled dosage, double the labeled dosage, and four times the labeled dosage.
• The concentrations of the drug in the urine and blood serum were then quantified and assessed.

Findings of the Study

• The results showed that the absorption and elimination of 1% liposomal diclofenac cream take place slowly in the horses’ bodies.
• As the dosage increased, the urinary and serum concentrations of the drug increased proportionally. However, even at four times the labeled dose, the diclofenac levels remained within the ‘safe’ limits, showing that the formulation is not only effective but also safe.

Implications and Utility of the Study

• The findings of this study are noteworthy, especially in the context of competitive horse racing, where the use of performance-enhancing drugs is monitored and penalized.
• Understanding the timelines required for diclofenac’s absorption and elimination can help estimate the necessary withdrawal time before a competition to prevent an accidental positive drug test.

This research contributes significantly to veterinary medicine and the fair regulation of competitive horse racing by providing an accurate measure of drug absorption and elimination rates within these animals following the use of a commonly applied NSAID (Non-Steroidal Anti-Inflammatory Drug), diclofenac. The data offers a practical and ethical guideline for equestrian sporting events regarding drug usage and withdrawal times.