l-METHYL-2-MERCAPTOIMIDAZOLE: A NEW ACTIVE ANTITHYROID AGENT*

Abstract

Tapazole (1-methyl-2-mercaptoimidazole), was found to be an effective antithyroid agent. Clinically it was found to be 10 times (or slightly more) as active as propylthiouracil. The suggested daily dose of Tapazole is 20 to 30 mg. for patients with primary hyperthyroidism and 30 to 40 mg. for patients with adenomatous goiters, the size of the goiter determining the size of the dose. There were 6 reactions from Tapazole in the 100 patients receiving treatment. In 3 patients treatment had to be withdrawn but in 3 patients further treatment with Tapazole was possible by altering the dose or by adding an antihistaminic drug. This experience with Tapazole indicates that it is an active antithyroid substance. The incidence of reactions is higher than with propylthiouracil (6% as compared with 1.6%), but none of the reactions was serious and agranulocytosis was not observed in the initial group of 100 patients studied. Since completion of this study, however, 1 case was observed in which severe granulocytopenia (15%) developed, indicating that this antithyroid drug also has toxic potentialities.