Antithyroid drugs (thionamides)
Antithyroid drugs block the thyroid gland from making thyroid hormone. Methimazole and propylthiouracil treat an overactive thyroid, such as in Graves disease, and prepare people for thyroid surgery or radioactive iodine. Rash, itching, joint pain, and upset stomach are common. A rare but serious drop in white blood cells can lead to severe infection, so a sore throat or fever is reported right away, and propylthiouracil can also cause severe liver injury.