The onset of inhibition is rapid and is readily demonstrated 30 minutes after oral administration. An important factor in obtaining satisfactory acute block of radioiodine uptake is the speed of iodide administration after exposure to radioiodine. It is clear from standard uptake curves that, after a single pulse of radioiodine, the bulk of it has entered the gland by 10 to 12 hours and little benefit may be expected by blocking beyond this time. For more prolonged iodine 131 exposure, iodide will be useful at any time during the exposure and hence should still be given even if the drug was not given shortly after the release of radioactivity. In case of overdose or allergic reaction, a physician should be contacted.
Thyrotoxicosis is unlikely to occur in iodine sufficient areas.
Patients with nodular goiter have an increased risk of thyrotoxicosis if they receive large doses of iodides for several weeks or longer. Monitor at 4 week intervals if the treatment is prolonged. Iodide goiter is rare after only a few weeks of iodide administration for limited periods of blocking. Respiratory obstruction of the infant by an enlarged thyroid should be looked for during delivery of women treated with iodide for any substantial period during pregnancy. Patients with thyroiditis or other known parenchymal tissue damage or with low thyroid reserve for unknown reasons, should be watched for a propensity to suffer iodide myxedema.