Antithyroid drug therapy includes medications that reduce the symptoms of thyrotoxicosis and decrease the synthesis and release of thyroid hormone. The most common definitive therapy for hyperthyroidism is ablation of the hyperactive thyroid with an oral dose of radioactive iodine (131 I). In some cases, the patient is treated with antithyroid medication to return thyroid hormone levels to normal. Often post antithyroid therapies, some patients (e.g., those with a toxic multinodular goiter or toxic adenoma) are treated immediately with radioactive iodine, while patients with autoimmune Graves’ disease may be treated for 12–18 months with antithyroid medications because of the possibility that the patient will go into remission. Patients with other forms of hyperthyroidism, including toxic multinodular goiter and toxic adenoma, continue to be thyrotoxic indefinitely. Remissions with antithyroid medications are not expected.