From the Guidelines
Methimazole is the preferred antithyroid medication for treating hyperthyroidism in pregnancy, as it has been found to have similar rates of fetal anomalies and no cases of aplasia cutis compared to propylthiouracil, as reported in the 2002 American College of Obstetricians and Gynecologists (ACOG) practice bulletin on thyroid disease in pregnancy 1. The goal of treatment with methimazole is to maintain FT4 or FTI in the high-normal range using the lowest possible dosage, with regular monitoring of thyroid function every two to four weeks.
- Key considerations for methimazole treatment include:
- Starting dose: typically ranges from 5 to 30 mg daily, depending on the severity of hyperthyroidism
- Maintenance therapy: 5-15 mg daily is common
- Side effects: rash, itching, joint pain, and rarely, more serious effects like agranulocytosis (decreased white blood cells)
- Monitoring: regular blood tests are necessary to monitor thyroid function and potential side effects Methimazole is often used to prepare patients for thyroid surgery or radioactive iodine therapy, or as a long-term treatment option, and its use in pregnant women is supported by the ACOG practice bulletin 1.
From the FDA Drug Label
Methimazole tablets, USP are indicated: In patients with Graves’ disease with hyperthyroidism or toxic multinodular goiter for whom surgery or radioactive iodine therapy is not an appropriate treatment option. To ameliorate symptoms of hyperthyroidism in preparation for thyroidectomy or radioactive iodine therapy. Methimazole inhibits the synthesis of thyroid hormones and thus is effective in the treatment of hyperthyroidism. Methinazole is used to treat hyperthyroidism caused by Graves’ disease or toxic multinodular goiter. The main mechanism of action is to inhibit the synthesis of thyroid hormones [2] [3].
From the Research
Methinazole Overview
- Methinazole, also known as MMI, is a medication used to treat hyperthyroidism, a condition where the thyroid gland produces excess thyroid hormones 4.
- It works by reducing the production of thyroid hormones in the thyroid gland.
Comparison with Propylthiouracil (PTU)
- Studies have compared the efficacy and safety of methinazole with propylthiouracil (PTU) in treating hyperthyroidism 5, 6, 7, 8.
- Methinazole has been found to be more effective in reducing thyroid hormone levels and has a lower risk of liver function damage compared to PTU 8.
- However, methinazole may have a higher risk of hypothyroidism compared to PTU 8.
Pregnancy Considerations
- Methinazole has been used to treat hyperthyroidism during pregnancy, but its use is generally recommended after the first trimester due to the risk of birth defects 5, 6.
- Propylthiouracil (PTU) is often recommended during the first trimester of pregnancy due to its lower risk of birth defects, but it may have a higher risk of liver injury 5, 6.