Further Studies of the Absorption, Distribution, and Elimination of Thiouracil1

IT IS NOW well established (1–8) that thiouracil is very effective in controlling thyrotoxicosis. However, it has been shown to have toxic effects which interfere with freedom in its use. It is possible that the frequency of complications from this drug can be appreciably reduced when more is known about its metabolism. The establishment of the minimal effective dosage in the treatment of thyrotoxicosis must be made clinically, but this may be hastened by biochemical studies of thiouracil. Although many estimations have been made of the concentration of thiouracil in the thyroid glands of thyro toxic patients (9), the minimal quantity of the drug necessary to cause adequate inhibition of thyroxin production has not been determined. In ascertaining this point it seems reasonable that the dosage of thiouracil should be adequate to keep its concentration in the blood at a fairly even level. In a previous report (10) we have described some of our studies dealing with the absorption, distribution and excretion of thiouracil.