What further treatment is required after a patient has received a dose of radioactive iodine?

Once a dose of radioactive iodine has been administered, it may take anywhere from a few weeks to several months for it to have its full effect. During this period, patients with severe thyrotoxicosis may continue to report symptoms related to exposure to excess levels of thyroid hormone. As such, they may require treatment with specific medications.

Patients who have been treated with beta blockers prior to the administration of a dose of radioactive iodine may be continued on them for several weeks after the dose has been administered. If treatment with radioactive iodine proves to be effective, doses of beta blockers can usually be decreased as symptoms associated with thyrotoxicosis gradually begin to subside. In most cases, beta blockers can eventually be discontinued altogether once a patient's hyperthyroidism has been brought under control.

Patients who have discontinued treatment with antithyroid drugs prior to the administration of a dose of radioactive iodine may or may not be restarted on them after the dose has been administered. Patients who initially presented with mild hyperthyroidism that proved to be easy to control with low doses of methimazole or propylthiouracil may fare just as well without any further treatment. This may not be the case in patients who initially presented with severe hyperthyroidism that was difficult to control or required treatment with high doses of methimazole or propylthiouracil. These patients may be at much greater risk of developing severe thyrotoxicosis after receiving a dose of radioactive iodine if they are not restarted on an antithyroid drug. In most cases, these patients can usually be restarted on doses that are lower than what they had taken up until the time of treatment. If treatment with radioactive iodine proves to be effective, doses of antithyroid drugs can usually be decreased as thyroid hormone levels begin to fall. In most cases, antithyroid drugs can eventually be discontinued altogether once thyroid hormone levels stabilize within normal ranges.

On occasion, patients who initially presented with severe hyperthyroidism may be started on treatment with a medication called potassium iodide after receiving a dose of radioactive iodine. Potassium iodide works to control hyperthyroidism by blocking the secretion of thyroid hormone from the thyroid gland. It is usually administered as a liquid in the form of a preparation called saturated solution of potassium iodide. Drops of this preparation are usually taken three times a day in a glass of juice. If treatment with radioactive iodine proves to be effective, potassium iodide can usually be discontinued as thyroid hormone levels begin to fall.