Potassium iodide is used to treat overactive thyroid and to protect the thyroid gland from the effects of radiation from inhaled or swallowed radioactive iodine. It may be used before and after administration of medicine containing radioactive iodine or after accidental exposure to radioactive iodine (for example, from nuclear power plant accidents that involved release of radioactivity to the environment).
Potassium Iodide is a white crystalline solid that is present in iodized salt, similar to table salt. Its chemical symbol is KI. It is routinely added to table salt to make it "iodized." Potassium iodide, if taken within the appropriate time and at the appropriate dosage, blocks the thyroid gland's uptake of radioactive iodine and thus reduces the risk of thyroid cancers and other diseases that might otherwise be caused by thyroid uptake of radioactive iodine that could be dispersed in a severe reactor accident.
Potassium iodide is an expectorant. It thins mucus secretions in the respiratory tract that may be caused by chronic respiratory problems such as asthma, chronic bronchitis, and emphysema. Potassium iodide is also used to protect the thyroid gland from radiation injury before and following administration of radioactive iodide (e.g., for diagnostic purposes) and in radiation emergencies (e.g., accidental exposure to radiation). The effectiveness of KI as a specific blocker of thyroid radioiodine uptake is well established. When administered in the recommended dose, KI is effective in reducing the risk of thyroid cancer in individuals or populations at risk for inhalation or ingestion of radioiodines. KI floods the thyroid with non-radioactive iodine and prevents the uptake of the radioactive molecules, which are subsequently excreted in the urine.
The thyroid is especially vulnerable during nuclear emergencies. Radioactive iodine is a major constituent used in nuclear power plants as well as in the fallout from nuclear detonation. Carried for hundreds of miles on the winds, if radioiodine is taken into the body through breathing or consumption of contaminated food, it is collected and retained by the thyroid gland. There, this concentration of radioactive material results in a variety of life-threatening illnesses including cancers and leukemia. Children -- born and unborn -- are particularly at risk due to their small physical size and weight. Potassium iodide saturates the thyroid with a safe, stable form of iodine, thus preventing the uptake of radioactive iodine. Potassium iodide is the only FDA approved thyroid-blocking agent and is approved for over the counter sale.