Comparison of antithyroid drug metabolism in the rat and guinea pig

Abstract

The thyroid accumulation, metabolism and urine excretion of (35S) propylthiouracil was compared in the guinea pig and the rat. Per gram thyroid tissue, the guinea pig thyroid took up much less drug than the rat, metabolised it faster and had a shorter t 1/2 for total 35S and free (35S) propylthiouracil. Liver metabolism, clearance of the drug from the serum and excretion in the urine were also considerably faster in the guinea pig. It is likely that a much larger dose of propylthiouracil would need to be administered to induce goitre in the guinea pig than is necessary in the rat.