Excretion mass balance evaluation, metabolite profile analysis and metabolite identification in plasma and excreta after oral administration of [14C]-meloxicam to the male cat: preliminary study.

The objective of this study was to investigate the metabolic pathways and routes of excretion of oral meloxicam in the cat. [(14)C]-meloxicam was administered orally to three fasted male cats. Urine, faeces, vomit and cage washes were collected over the following 144 h period. Blood was collected predosing and at 3 and 12 h postdosing. Metabolites were identified by HPLC/MS/MS. When possible a metabolic structure was proposed for each metabolite detected. Only unchanged meloxicam was identified in plasma. Five major metabolites were detected in urine and four in faeces, which were identified by HPLC/MS/MS as products of oxidative metabolism. No conjugated metabolites were detected. Elimination occurred early (61% during the first 48 h). A total of 21% of the recovered dose was eliminated in urine (2% as unchanged meloxicam, 19% as metabolites) and 79% in the faeces (49% as unchanged meloxicam, 30% as metabolites). The results indicate that after oral administration the major route of excretion of meloxicam in the cat is faecal and that the main pathway of biotransformation of meloxicam in the cat is oxidation.