Investigation of the metabolism of azaperone in the horse

Abstract

Urine samples collected from a horse after intramuscular administration of 40 mg of azaperone were extracted at pH 10 before and after acid hydrolysis. The extracts were concentrated and analysed by LC—MS—MS. Two N-dealkylated metabolites, N-despyridinylazaperol and N-despyridinylazaperone, and a low concentration of azaperone were detected in the unhydrolysed urine. Six metabolites; hydroxyazaperol, two hydroxyazaperones, azaperol, N-despyridinylazaperol and N-despyridinylazaperone were detected in the hydrolysed urine extracts. Using XAD-2 resin extraction, three glucuronide conjugated azaperone metabolites (hydroxyazaperol glucuronide, hydroxyazaperone glucuronide and azaperol glucuronide) were detected in the urine. The mass spectra of these metabolites show the same characteristic daughter ions as the unconjugated metabolites. The glucuronide conjugated azaperone metabolites were partially hydrolysed in the heated nebulizer interface to the unconjugated metabolites.