From the FDA Drug Label
DOSAGE AND ADMINISTRATION Methimazole tablets, USP are administered orally. The total daily dosage is usually given in 3 divided doses at approximately 8-hour intervals. Adult The initial daily dosage is 15 mg for mild hyperthyroidism, 30 mg to 40 mg for moderately severe hyperthyroidism and 60 mg for severe hyperthyroidism, divided into 3 doses at 8-hour intervals. The maintenance dosage is 5 mg to 15 mg daily. The typical dose of methimazole for hyperthyroidism is:
- Initial dose:
- 15 mg daily for mild hyperthyroidism
- 30 mg to 40 mg daily for moderately severe hyperthyroidism
- 60 mg daily for severe hyperthyroidism
- Maintenance dose: 5 mg to 15 mg daily 1
From the Research
The typical starting dose of methimazole for hyperthyroidism is 15 mg daily, as this dose has been shown to be effective in inducing euthyroidism while minimizing adverse effects 2. When considering the treatment of hyperthyroidism with methimazole, the dose and administration schedule are crucial for achieving optimal outcomes.
- The severity of hyperthyroidism plays a significant role in determining the initial dose, with mild cases potentially requiring lower doses and severe cases necessitating higher doses.
- Studies have compared the efficacy of once-daily versus divided-daily administration of methimazole, with findings suggesting that a low daily dosage of 15 mg can be effective in inducing euthyroidism, regardless of the administration schedule 2.
- However, the once-daily regimen may be preferable due to a lower risk of hypothyroidism compared to the divided-daily regimen 2.
- Methimazole works by inhibiting thyroid peroxidase, an enzyme essential for thyroid hormone production, thereby reducing thyroid hormone levels and alleviating symptoms of hyperthyroidism.
- Common side effects of methimazole include rash, itching, and gastrointestinal upset, and patients should be monitored regularly with thyroid function tests to adjust the dose as needed and minimize the risk of adverse effects 3, 4, 5.
- It is also important to note that methimazole crosses the placenta and is present in breast milk, so dosing adjustments may be necessary for pregnant or breastfeeding women.
- The goal of treatment is to achieve euthyroidism, which is typically accomplished within 6-12 weeks, after which the dose can be gradually reduced to a maintenance dose of 5-15 mg daily.