Efficacy of different starting doses of methimazole (mercazolil) in the treatment of diffuse toxic goiter
The purpose of this study was to investigate the effects of two different starting doses of methimazole (MMI) on the clinical and biochemical characteristics of patients with Grave's disease and, specifically, to elucidate the effects of various independent factors on the efficacy of MMI. Sixty untreated hyperthyroid patients were enrolled in the trial. Forty-six cases were newly diagnosed, 6 patients presented with relapse following prior therapy or surgery. Eight patients previously treated with MMI in a dose of 30 mg had to interrupt the treatment because of grave side effects; in our study they were administered the drug in a dose of 15 mg. All patients were residents of Russia, living in areas with moderate and mild iodine deficiency; they were divided in two equal groups, A and В with the starting daily doses of 15 and 30 mg MMI, respectively. Free T4 levels in the serum were measured and clinical examinations carried out 3, 4, and 5 weeks after the beginning of MMI therapy. In group A, 86.7% (26/30) patients were euthyroid after 3 weeks and 100% after 4 weeks versus 93.3 (28/30) and 96.7% (29/30) in group B. The time of euthyroidism onset did not depend on the starting dose of the drug (3.130.11 weeks in group A vs. 3.100.12 weeks in group B). No correlation could be traced between the dose efficacy and patients' age, disease standing, size of the thyroid, or presence of endocrine ophthalmopathy. Euthyroidism was attained significantly earlier in group В in comparison with group В (3.00 vs. 4.40.3 weeks) only in patients with very high initial levels of free T4 (75 pmole/liter). There was only one case with minor complications in group A and two cases in group B. In addition, 8 patients in group A with a history of side effects of therapy with MMI in a dose of 30 mg were administered the drug in a dose reduced by half without adverse effects. Our data confirm the previous results that response to thyroid drugs depends mainly on the pretreatment free T4 levels. The majority of patients with Graves' disease from regions with iodine deficiency can be effectively controlled by small starting doses of MMI (e.g., 15 mg) with a lower risk of dose-dependent side effects.