Efficacy of single daily dosage of methimazole vs. propylthiouracil in theinduction of euthyroidism

OBJECTIVE Previous studies of the treatment of hyperthyroidism with a singl e daily dose of antithyroid drugs have demonstrated a favourable result wit h methimazole (MMI). However, the efficacy of a single daily dose of propyl thiouracil (PTU) was inconsistent. The present prospective randomized study was conducted to compare the efficacy of a single daily dose of MMI and PT U in the induction of euthyroidism in patients with Graves' disease. SUBJECTS Seventy-one patients with newly diagnosed Graves' disease were stu died. METHODS AND MEASUREMENTS Patients were randomized to two groups to receive once daily dose of either 15 mg MMI or 150 mg PTU for 12 weeks. The therape utic efficacy was determined biochemically by serum total T3, total T4 and TSH levels at baseline and at 4, 8 and 12 weeks during the study period. RESULTS There was no significant difference in baseline characteristics. Se rum total T3 levels of the MMI group were significantly lower than those of the PTU group after four weeks of the treatment (3.54 +/- 0.72 vs. 5.49 +/ - 2.74 nmol/l, P < 0.05) through the end of the study (2.22 +/- 1.42 vs. 4. 30 +/- 1.78 nmol/l, P < 0.05). The changes in serum total T4 levels occurre d in the same direction as serum total T3 levels but a significant differen ce was observed only after eight weeks of the treatment (MMI vs. PTU; 101.6 7 +/- 54.05 vs. 176.32 +/- 66.92 nmol/l, P < 0.05). At the end of the study , more patients in the MMI group had both serum total T3 and T4 levels less than the upper limit of the normal range compared to the PTU group (77.1% vs. 19.4%). Hypothyroidism was observed in 31.4% of the patients in the MMI group but not in the PTU group. CONCLUSIONS During 12-weeks' treatment of Graves' hyperthyroidism, a single daily dose of 15 mg of MMI was much more effective in the induction of eut hyroidism than a single daily dose of 150 mg of PTU. Once daily regimen of MMI not only decreased serum T3 and T4 levels more rapidly but also induced euthyroidism four times more effectively than did the once daily regimen o f PTU. In the doses used in this study, MMI is preferable to PTU when a onc e-daily regimen of antithyroid drug is considered for the treatment of hype rthyroidism.