What is the first medication typically used to treat thyrotoxicosis in pregnancy?

The first medication typically used to treat thyrotoxicosis in pregnancy is propylthiouracil (PTU). This choice is based on PTU's effectiveness in controlling hyperthyroidism while being relatively safe for use during pregnancy, especially during the first trimester.

Thyrotoxicosis in pregnancy is often related to conditions such as Graves’ disease, and managing this condition is crucial to ensure the health of both the mother and the developing fetus. PTU works by inhibiting the synthesis of thyroid hormones and has a lower risk of crossing the placenta compared to methimazole, making it a preferred choice particularly in early pregnancy.

While methimazole is also used to manage hyperthyroidism, its association with congenital malformations when taken in early pregnancy has led to a preference for PTU during this critical time in gestation. Levothyroxine, on the other hand, is a thyroid hormone replacement and is not indicated for treating hyperthyroidism. Thyroid hormone replacement therapy would not be appropriate for thyrotoxicosis since the aim is to reduce thyroid hormone levels rather than replace them.