A low dose of methimazole is nearly as effective and is safer than a higher dose of methimazole or propylthiouracil in patients with Graves’ hyperthyroidism
(July 2007)
The background of the study. Many patients with hyperthyroidism are treated with methimazole or propylthiouracil. In this study, the efficacy and safety of these drugs was evaluated in patients with hyperthyroidism caused by Graves’ disease.
How the study was done. The study subjects were 303 patients with Graves’ hyperthyroidism (mean age, 40 years). The patients were randomly assigned to treatment with 15 mg of methimazole once daily, 15 mg of methimazole twice daily, or 100 mg of propylthiouracil three times daily for 12 weeks. They were evaluated and liver function and serum free T4 were measured at base line and after treatment for 4, 8, and 12 weeks.
The results of the study. A total of 263 patients completed the 12-week study. The most effective treatment at all times was 30 mg of methimazole daily, but the differences in favor of this dose were small (Table 1).
| Table 1. Frequency of Normal Serum Free T4 Concentrations in Patients with Graves’ Hyperthyroidism Treated with Methimazole or Propylthiouracil.* |
| Dose |
4 Weeks |
8 Weeks |
12 Weeks |
| Methimazole, 15 mg/day |
37% |
70% |
86% |
| Methimazole, 30 mg/day |
53% |
81% |
96% |
| Propylthiouracil, 300 mg/day |
38% |
68% |
78% |
The overall frequency of adverse effects and that of most specific adverse effects were lowest in the patients treated with 15 mg of methimazole daily (Table 2).
| Table 2. Adverse Effects of Methimazole and Propylthiouracil. |
| |
Methimazole 15 mg/day |
Methimazole
30 mg/day |
Propylthiouracil 300 mg/day |
| Total adverse effects |
14% |
30% |
52% |
| Drug changed or stopped |
7% |
22% |
38% |
| Liver toxicity |
7% |
7% |
27% |
| Hives or other skin rash |
7% |
22% |
22% |
The conclusions of the study. Treatment of patients with hyperthyroidism with 15 mg/day of methimazole is almost as effective as and is safer than treatment with 30 mg/day of methimazole or 300 mg/day of propylthiouracil.
The original article. Nakamura H, Noh JY, Itoh K, Fukata S, Miyauchi A, Hamada N. Comparison of methimazole and propylthiouracil in patients with hyperthyroidism caused by Graves’ disease. J Clin Endocrinol Metab 2007;92:2157-62.
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