The isolation and identification of 14C-sulfamethazine (4-amino-n-(4,6-dimethyl-2-pyrimidinyl)[14C]benzenesulfonamide) metabolites in the tissues and excreta of swine

Pigs were given a single oral dose of 14C-sulfamethazine (4-amino-N(I4,6-dimethyl-2-pyrimidinyl)14C]benzenesulfonamide). Approximately 78% of the 14C was eliminated in the urine and 18% was eliminated in the feces within 192 hr after dosing. The percentage of the 14C remaining in the animals after dosing was as follows: 6 hr, 88%; 24 hr, 49%; 48 hr, 14%; 192 hr, less than 1%. The 14C-labeled compounds in the tissues and excreta were isolated by solvent extraction and by conventional and high-pressure liquid chromatography, and then derivatized and characterized by infrared and mass-spectral analysis. Chemical structures were confirmed by synthesis. The major 14C-labeled compounds in the skeletal muscle, liver and kidney were identified as sulfamethazine, N4-acetylsulfamethazine, the N4-glucose conjugate of sulfamethazine, and N-(4,6-dimethyl-2-pyrimidinyl)benzenesulfonamide (desaminosulfamethazine). The major 14C-labeled compounds in the urine and feces were identified as sulfamethazine and N4-acetylsulfamethazine.