Metabolism of 35S-labelled antithyroid drugs in man.

Differences in the metabolic fate of antithyroid drugs influence the optimal frequency of administration and their therapeutic efficacy. (35)S propylthiouracil differed from the (35)S imidazoles (carbimazole and methimazole) in the more rapid absorption and excretion and the shorter biological half-life in the plasma of the former. Renal function may have a more important influence on the biological half-life of the drugs than thyroid status. Further work is required to determine the optimal frequency of administration for each compound.