Mechanism of Action:
Similar to PTU, Methimazole inhibits thyroid peroxidase, thereby preventing the synthesis of thyroid hormones.
However, unlike PTU, Methimazole does not inhibit the peripheral conversion of T4 to T3.
Uses:
Methimazole is commonly used in the treatment of hyperthyroidism, particularly in Graves' disease.
It's preferred over PTU in most cases due to a lower incidence of severe side effects.
Considerations:
While Methimazole is generally safer than PTU, it can still cause side effects like skin rash, joint pain, and in rare cases, agranulocytosis.
It's typically avoided in the first trimester of pregnancy due to a slightly higher risk of congenital abnormalities.
Both medications require careful dosing and regular monitoring, including thyroid function tests and blood cell counts.
The choice between Propylthiouracil and Methimazole depends on the patient’s specific circumstances, including pregnancy status, severity of hyperthyroidism, and potential side effects.
The goal of therapy is to achieve a euthyroid state, where thyroid hormone levels are normal.