The detection of piroxicam, tenoxicam and their metabolites in equine urine by electrospray ionisation ion trap mass spectrometry.

The research is revolved around how horses metabolize two common veterinary drugs, piroxicam and tenoxicam,4 and what these drugs become once broken down in the horse’s body. This knowledge can help scientists and veterinarians better understand drug excretion in horses and develop more accurate drug tests for the sport.

Research Objectives and Methods

• The primary aim of the study was to observe the metabolism and excretive process of two orally administered drugs (piroxicam and tenoxicam) in horses.
• The researchers checked these components in horse urine for up to 72 hours after the administration of the drugs.
• The mass spectral characteristics of the drugs and their metabolites were examined using ion trap mass spectrometry, a method allowing for very precise measurements of chemical substances.

Key Findings

• After the administration of piroxicam, the major component found in the horse’s urine was 5′-hydroxypiroxicam, which was observable up to 24 hours post-administration. Piroxicam itself was found only as a minor component.
• In the case of tenoxicam, the drug was the major component found in the urine, and it was detectable for up to 72 hours post-administration. Its metabolite, 5′-hydroxytenoxicam, was found only in small amounts.
• The study also found that the phase of metabolism that involves conjugation with glucuronic acid (Phase II beta-glucuronide conjugation) was negligible in the breakdown of both drugs.

Implications

• The findings contribute to our understanding of how these drugs are broken down and excreted in equine physiology. By showing how long the drug and its metabolites remain in the horse’s system, the results could help in designing drug tests or informing dosage guidelines for horses.
• The negligible conjugation with glucuronic acid suggests that these two drugs follow a different metabolic pathway than some other drugs.