INVESTIGATION OF THE METABOLISM OF AZAPERONE IN THE HORSE

Urine samples collected from a horse after intramuscular administratio n 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. T wo N-dealkylated metabolites, N-despyridinylazaperol and N-despyridiny lazaperone, and a low concentration of azaperone were detected in the unhydrolysed urine. Six metabolites; hydroxyazaperol, two hydroxyazape rones, azaperol, N-despyridinylazaperol and N-despyridinylazaperone we re detected in the hydrolysed urine extracts. Using XAD-2 resin extrac tion, three glucuronide conjugated azaperone metabolites (hydroxyazape rol glucuronide, hydroxyazaperone glucuronide and azaperol glucuronide ) were detected in the urine. The mass spectra of these metabolites sh ow the same characteristic daughter ions as the unconjugated metabolit es. The glucuronide conjugated azaperone metabolites were partially hy drolysed in the heated nebulizer interface to the unconjugated metabol ites.