Characterization of in vivo plasma metabolites of tepoxalin in horses using LC-MS-MS.

The study investigated the metabolic pathway of tepoxalin, a veterinary drug, in horses using liquid chromatography-mass spectrometry (LC-MS-MS) techniques.

Introduction to Tepoxalin

• Tepoxalin is a dual inhibitor veterinary drug that acts via blocking the cyclooxygenase-5 lipoxygenase pathway. It is registered for usage in dogs.
• In horses, tepoxalin primarily acts by inhibiting cyclooxygenase, an activity believed to be triggered by its metabolites.
• Out of the tepoxalin metabolites in horses, only RWJ-20142 is well-known, with little to no information available about the other in vivo metabolites.
• Understanding the primary metabolic pathway of tepoxalin in horses is crucial for better comprehension of its clinical activity.

Methodology

• The research utilized a suitable high-performance liquid chromatography (HPLC) method which was applied to LC-MS-MS for identification and characterization of the main metabolites.
• This was performed with horses orally given tepoxalin, and the main metabolites in their plasma were investigated.
• Mass spectrometry was employed in full scan, product ion scan, and precursor ion scan modes which assisted in identifying most parts of the unknown metabolite structures.

Findings and Implications

• The discovered structures of unknown metabolites were found to be closely related to that of tepoxalin, the parent drug.
• It was speculated that one of the metabolites might be a structural isomer of tepoxalin.
• The discoveries from this research add valuable knowledge to comprehend the pharmacology of tepoxalin in horses.
• The findings could potentially inform veterinary medicine use and administration, ensuring maximum efficacy and safety.