Potassium iodide is used to loosen and break up mucus in the airways. This helps you cough up the mucus so you can breathe more easily if you have long-term lung problems (e.g., asthma, chronic bronchitis, emphysema). This medication is known as an expectorant.
Potassium iodide is also used along with antithyroid medicines to prepare the thyroid gland for surgical removal, to treat certain overactive thyroid conditions (hyperthyroidism), and to protect the thyroid in a radiation exposure emergency. It works by shrinking the size of the thyroid gland and decreasing the number of thyroid hormones produced.
In a radiation emergency, potassium iodide blocks only the thyroid from absorbing radioactive iodine, protecting it from damage and reducing the risk of thyroid cancer. Use this medication along with other emergency measures that will be recommended to you by public health and safety officials (e.g., finding safe shelter, evacuation, controlling food supply).