Metabolism of 6-methyl-2-thiouracil was studied in rats by using 14C-labeled compound. Following the oral administration of 6-methyl-2-thiouracil [2-14C] (490 mg/kg), the about 68% of the administered radioactivity was excreted in urine, 27% in feces, and 1.2% in respiratory CO2 within 72 hr. After oral ingestion of the radioactive compound, radioactive substances excreted in urine after 48 hr were 6-methyl-2-thiouracil, 6-methyl-uracil, 6-methyl-2-methylthiouracil, 6-methyl-4-oxo-pyrimidine, 2-amino-6-methyl-4-oxopyrimidine, and urea which were present in about 46.2, 9.1, 1.6, 1.8, 0.2, and 0.8% of total radioactivity in the urine, respectively. In in vitro tests using rat liver slices, radioactivity was also detected in 5, 6-dihydro-6-methyluracil along with the above metabolites.
