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Potassium Iodide for Radiation Exposure

IOSAT Package

Potassium iodide was approved by the Food and Drug Administration(FDA) in 1982 for thyroid protection from radioactive iodine accidents.  Of the many radioactive elements released by nuclear accidents, radioactive Iodine-131 is a major component and a huge risk factor for humans.

Potassium iodide is a salt form of stable iodine (non-radioactive iodine), and works by blocking radioactive iodine uptake and binding in our thyroid tissue.  Non-radioactive potassium iodide is instantly absorbed by the thyroid, binds to the thyroid tissue to saturation, and inhibits the absorption of “radioactive” iodine for up to 24 hours.   However, excess iodine is not without complications, particularly in infants, as it inhibits the production of thyroid hormones and can cause hypothyroidism in infants.   Further, iodine, whether radioactive or non-radioactive is transported to a high level in human or animal milk.  Thus, breastfeeding mothers should use great caution in using potassium iodide.

In the event of a radioactive emergency, the CDC recommends that potassium iodide be taken by the following groups:

Infants (including those who are breastfeeding)- The normal amount of potassium iodide present in breast milk is not sufficient to protect an infant who has been exposed to radioactive Iodine-131.   Thus, infants exposed to environmental radioactive Iodine-131 or other forms of radioactive iodine must receive Potassium Iodide to block uptake of radiation in the infant’s thyroid gland.

Remember, radioactive iodine passes into any form of mammalian milk, and at high levels.  Radioactive iodine exposure in infants (and less so in adults) may lead to higher rates of thyroid cancer.  Infants exposed to excessively high radiation levels, should probably use some form of formula if available along with Potassium Iodide.    If formula is unavailable, the infant should continue to breastfeed, and both mother and infant should receive oral Potassium Iodide supplements as recommended.

Recommended Dose in Infants: 16 mg once daily (<1 month old), 32 mg once daily (1-36 months old).  The duration depends on the level and duration of exposure to radioactive iodine.  Prolonged usage (> 10 days) could lead to hypothyroidism and the infant should be monitored for thyroid function. This is exceedingly important in young infants.

Children- Children between the ages of 0-18 years of age are considered to be at high risk for the potentially harmful effects of radioactive iodine.  It is recommended that they take potassium iodide if they are being exposed to radioactive iodine.  Recommended Dose: 65 mg once daily (ages 3-12 years)

Pregnant Women- Pregnant women should take potassium iodide to protect their fetus because all forms of iodine can cross the placenta.  Pregnant women should only take potassium iodide if they are contaminated with radioactive iodine.  The unnecessary use of potassium iodide by a pregnant woman can suppress the developing thyroid in the fetus.   Recommended Dose: 130 mg once daily

Breastfeeding Women- Women who are breastfeeding should take potassium iodide as well. Breastfeeding women should only take potassium iodide if they are contaminated with radioactive iodine and advised to do so by their governmental agencies.  Radioactive iodine gets into breast milk avidly and therefore can transfer to the breastfed baby.  Recommended Dose: 130 mg once daily.

Adults- Adults over the age of 40 should not take potassium iodide unless officials in the area affected state that there is a very high level of radioactive iodine contamination.  This group is the least likely to develop thyroid cancer or thyroid injury.  This group is also at a higher risk for developing potassium iodide allergies.  Recommended Dose: 130 mg once daily

Potassium iodine should be used cautiously and ONLY in humans exposed to radioactive iodine.  You should follow the guidelines and advice of your governments public health departments.  At present, NO environmental radioactive I-131 has been detected in the USA, or most other countries.  Because potassium iodide has significant risks associated with its use, particularly in breastfed infants and newborns, mothers should avoid using it if at all possible.

Taking a higher dose or more frequent doses can result in adverse health effects and can even be fatal.  Finally, ONLY use potassium iodide if you are advised to by your physician or government health care agency, and ONLY if you are exposed to high levels of radioactive Iodine.


Thomas W. Hale, Ph.D.
Maria Milla, MD

InfantRisk Center
Texas Tech University School of Medicine

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