What is Potassium Iodide (KI)?
KI (potassium iodide) is a salt of stable (not radioactive) iodine that can help block radioactive iodine from being absorbed by the thyroid gland, thus protecting this gland from radiation injury. The thyroid gland is the part of the body that is most sensitive to radioactive iodine. People should take KI (potassium iodide) only on the advice of public health or emergency management officials.
There are health risks associated with taking KI. KI (potassium iodide) does not keep radioactive iodine from entering the body and cannot reverse the health effects caused by radioactive iodine once the thyroid is damaged. KI (potassium iodide) only protects the thyroid, not other parts of the body, from radioactive iodine. KI (potassium iodide) cannot protect the body from radioactive elements other than radioactive iodine—if radioactive iodine is not present, taking KI is not protective and could cause harm. Table salt and foods rich in iodine do not contain enough iodine to block radioactive iodine from getting into your thyroid gland. Do not use table salt or food as a substitute for KI. Do not use dietary supplements that contain iodine in the place of KI (potassium iodide). They can be harmful and non-efficacious. Only use products that have been approved by the U.S. Food and Drug Administration (FDA).
How does KI (potassium iodide) work?
The thyroid gland cannot tell the difference between stable and radioactive iodine. It will absorb both.
KI (potassium iodide) blocks radioactive iodine from entering the thyroid. When a person takes KI, the stable iodine in the medicine gets absorbed by the thyroid. Because KI contains so much stable iodine, the thyroid gland becomes “full” and cannot absorb any more iodine—either stable or radioactive—for the next 24 hours.
KI (potassium iodide) may not give a person 100% protection against radioactive iodine. Protection will increase depending on three factors.
- Time after contamination: The sooner a person takes KI, the more time the thyroid will have to “fill up” with stable iodine.
- Absorption: The amount of stable iodine that gets to the thyroid depends on how fast KI is absorbed into the blood.
- Dose of radioactive iodine: Minimizing the total amount of radioactive iodine a person is exposed to will lower the amount of harmful radioactive iodine the thyroid can absorb.
Before taking potassium iodide:
- tell your doctor and pharmacist if you are allergic to potassium iodide, iodine, any other medications, or any of the ingredients in potassium iodide tablets or liquid. Ask your pharmacist or check the package label for a list of the ingredients.
- tell your doctor and pharmacist what prescription and nonprescription medications, vitamins, nutritional supplements, and herbal products you are taking or plan to take. If you are unable to reach your doctor, you may take potassium iodide along with your other medications.
- tell your doctor if you have dermatitis herpetiformis (an ongoing skin disease that causes groups of itchy blisters to form on the body), hypocomplementemic vasculitis (an ongoing condition that causes frequent outbreaks of hives and other symptoms such as swelling and joint pain), or if you have both multinodular thyroid disease (many lumps in the thyroid gland) and heart disease. You should not take potassium iodide if you have any of these conditions.
- if you have or have ever had a thyroid condition such as Graves disease (condition where the body attacks the thyroid gland causing it to be overactive) or Hashimoto's thyroiditis (swelling of the thyroid gland that causes its function to decrease), you may take potassium iodide if you are told to so in an emergency. However, you should call your doctor if you need to take potassium iodide for more than a few days.
- tell your doctor if you are pregnant, plan to become pregnant, or are breast-feeding. If you are pregnant or breast-feeding, you may take potassium iodide if you are told to do so in an emergency, but you should call your doctor as soon as possible. Your doctor will probably monitor you carefully, and will want you to avoid taking more than one dose of potassium iodide if possible.
- if you give potassium iodide to a baby younger than one month of age, call the baby's doctor as soon as possible. The baby's doctor will monitor the baby carefully and will want you to avoid giving the baby more than one dose of potassium iodide if possible.
Who can take KI (potassium iodide)?
The thyroid glands of a fetus and of an infant are most at risk of injury from radioactive iodine. Young children and people with low amounts of iodine in their thyroid are also at risk of thyroid injury.
Infants (including breast-fed infants)
Infants have the highest risk of getting thyroid cancer after being exposed to radioactive iodine. All infants, including breast-fed infants need to be given the dosage of KI (potassium iodide) recommended for infants.
- Infants (particularly newborns) should receive a single dose of KI. More than a single dose may lead to later problems with normal development. Other protective measures should be used.
- In cases where more than one dose is necessary, medical follow up may be necessary.
Children
The U.S. Food and Drug Administration (FDA) recommends that all children internally contaminated with (or likely to be internally contaminated with) radioactive iodine take KI (potassium iodide), unless they have known allergies to iodine (contraindications).
Young Adults
The FDA recommends that young adults (between the ages of 18 and 40 years) internally contaminated with (or likely to be internally contaminated with) radioactive iodine take the recommended dose of KI (potassium iodide). Young adults are less sensitive to the effects of radioactive iodine than are children.
Pregnant Women
Because all forms of iodine cross the placenta, pregnant women should take KI (potassium iodide) to protect the growing fetus. Pregnant women should take only one dose of KI following internal contamination with (or likely internal contamination with) radioactive iodine.
Breastfeeding Women
Women who are breastfeeding should take only one dose of KI (potassium iodide) if they have been internally contaminated with (or are likely to be internally contaminated with) radioactive iodine. They should be prioritized to receive other protective action measures.
Adults
Adults older than 40 years should not take KI (potassium iodide) unless public health or emergency management officials say that contamination with a very large dose of radioactive iodine is expected.
- Adults older than 40 years have the lowest chance of developing thyroid cancer or thyroid injury after contamination with radioactive iodine.
- Adults older than 40 are more likely to have allergic reactions to or adverse effects from KI.
How is KI (potassium iodide) given?
The FDA has approved two different forms of KI (potassium iodide), tablets and liquid, that people can take by mouth after a radiation emergency involving radioactive iodine.
Tablets come in two strengths, 130 milligram (mg) and 65 mg. The tablets have lines on them so that they may be cut into smaller pieces for lower doses.
For the oral liquid solution, each milliliter (mL) contains 65 mg of KI (potassium iodide).
According to the FDA, the following doses are appropriate to take after internal contamination with (or likely internal contamination with) radioactive iodine:
- Newborns from birth to 1 month of age should be given 16 mg (¼ of a 65 mg tablet or ¼ mL of solution). This dose is for both nursing and non-nursing newborn infants.
- Infants and children between 1 month and 3 years of age should take 32 mg (½ of a 65 mg tablet OR ½ mL of solution). This dose is for both nursing and non-nursing infants and children.
- Children between 3 and 18 years of age should take 65 mg (one 65 mg tablet OR 1 mL of solution). Children who are adult size (greater than or equal to 150 pounds) should take the full adult dose, regardless of their age.
- Adults should take 130 mg (one 130 mg tablet OR two 65 mg tablets OR two mL of solution).
- Women who are breastfeeding should take the adult dose of 130 mg.
How often should KI (potassium iodide) be taken?
Taking a stronger dose of KI (potassium iodide), or taking KI more often than recommended, does not offer more protection and can cause severe illness or death.
A single dose of KI (potassium iodide) protects the thyroid gland for 24 hours. A one-time dose at recommended levels is usually all that is needed to protect the thyroid gland.
In some cases, people can be exposed to radioactive iodine for more than 24 hours. If that happens, public health or emergency management officials may tell you to take one dose of KI (potassium iodide) every 24 hours for a few days.
Avoid repeat dosing with KI (potassium iodide) for pregnant and breastfeeding women and newborn infants.
What are the side effects of KI (potassium iodide)?
Side effects of KI (potassium iodide) may include stomach or gastro-intestinal upset, allergic reactions, rashes, and inflammation of the salivary glands.
When taken as recommended, KI (potassium iodide) can cause rare adverse health effects related to the thyroid gland.
These rare adverse effects are more likely if a person:
- Takes a higher than recommended dose of KI
- Takes the drug for several days
- Has a pre-existing thyroid disease.
Newborn infants (less than 1 month old) who receive more than one dose of KI (potassium iodide) are at risk for developing a condition known as hypothyroidism (thyroid hormone levels that are too low). If not treated, hypothyroidism can cause brain damage.
- Infants who receive more than a single dose of KI should have their thyroid hormone levels checked and monitored by a doctor.
- Avoid repeat dosing of KI to newborns.
Where can I get KI (potassium iodide)?
KI (potassium iodide) is available without a prescription in pharmacy. The Food and Drug Administration (FDA)external icon External Web Site Icon has approved some brands of KI.
People should only take KI (potassium iodide) on the advice of public health or emergency management officials. There are health risks associated with taking KI.
More detailed information on KI (potassium iodide) can be found at the FDA Website.
What should I know about storage and disposal of this medication?
Keep this medication in the container it came in, tightly closed, and out of reach of children. Store it at room temperature and away from light, excess heat and moisture (not in the bathroom). Some bottles of potassium iodide may be safe to use after the expiration date stamped on the bottle; ask your doctor or pharmacist for more information.
Unneeded medications should be disposed of in special ways to ensure that pets, children, and other people cannot consume them. However, you should not flush this medication down the toilet. Instead, the best way to dispose of your medication is through a medicine take-back program. Talk to your pharmacist or contact your local garbage/recycling department to learn about take-back programs in your community. See the FDA's Safe Disposal of Medicines website (http://goo.gl/c4Rm4p) for more information if you do not have access to a take-back program.
Sources:
https://www.health.ny.gov/environmental/radiological/potassium_iodide/fact_sheet.htm
https://www.cdc.gov/nceh/radiation/emergencies/ki.htm
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