Metabolism of thymoxamine. III. Structure elucidation of the metabolites and interspecies comparison.

The structures of six metabolites were elucidated using rat urine after intragastric administration of 14C-thymoxamine by means of enzyme incubations, mass spectrometry and synthesis of metabolites: desacetylthymoxamine, N-demethyl-desacetylthymoxamine, the corresponding sulfates and glucuronides. The nature of the conjugates was confirmed by biosynthesis, i.e., co-administration of unlabelled thymoxamine and 35S-sulfate or 14C-glucose. The system high performance liquid chromatography-radioactivity detection was used for interspecies comparison. All biotransformation pathways are seen in rat and man. In dog and cat demethylation is a very minor reaction. Glucuronidation is not observed in the cat.