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Potassium Iodide

The objective of this article is to provide information about the effective use of potassium iodide (KI) as an adjunct to other protective health measures in the event that radioactive iodine is released into the environment.

What is Potassium Iodide?

Potassium iodide is an inorganic compound of potassium and iodide. Aged pills turn yellow because of oxidation of the iodide to iodine. Potassium iodide is medicinally supplied in both tablets and a "saturated solution of potassium iodide" (SSKI) for emergency purposes. Two (2) drops of U.S.P. SSKI solution is equivalent to one 130 mg KI tablet (100 mg iodide).

How does Potassium Iodide work?

Taking potassium iodide tablets saturates the thyroid gland with non-radioactive iodine. This reduces the ability of the thyroid to absorb additional iodide, including the radioactive iodine (radioiodines) released by radioactive materials in fallout. If the body is exposed to fallout while the thyroid is saturated, the radioactive iodine is excreted in the urine rather than being absorbed by the thyroid. Inhaling radioactive iodine from fallout without the benefit of potassium iodide is known to cause thyroid cancer.

The protective effect of KI lasts approximately 24 hours. KI works best if used within 3-4 hours of exposure.

How long should we take Potassium Iodide?

For maximum protection, KI must be taken daily until the risk of significant exposure to radioiodine by either inhalation or ingestion no longer exists. Not all sources are in agreement on the necessary duration of thyroid blockade.

Can potassium iodide (KI) be used to protect against radiation from fallout other than radioactive iodine?

No, potassium iodide (KI) works only to prevent the thyroid from absorbing radioactive iodine. It does not protect from other types of fallout or radioactive exposure.

Who needs to take potassium iodide?

After determining the risk for radioiodine-induced thyroid cancer, the FDA has set priorities for groups based on age.
  • The highest risk groups are infants, children, pregnant women, and nursing mothers. The FDA recommends treating those in this group at the lowest threshold (with respect to predicted radioactive dose to the thyroid).
  • Anyone between the age of 18 and 40 should be treated at a slightly higher threshold.
  • Those over 40 should be treated with KI only if the predicted exposure is high enough to destroy the thyroid and induce lifelong hypothyroidism (thyroid deficiency).

What potassium iodide (KI) products are currently available?

If you live in the USA, the only KI products legally available are those approved by FDA. As of January 2005, only 3 KI products have FDA approval: Iosat, ThyroSafe, and ThyroShield.

These products are distributed by state, local and federal agencies, as well as the following businesses:
  • Anbex, Inc. for Iosat Tablets (130 mg) at 212-580-2810 (M-F 9am-5pm), at 1-866-463-6754 (other times)
  • ThyroSafe Tablets (65 mg) at 1-866-849-7672
  • Fleming & Company, Pharmaceuticals for ThyroShield Solution at 636-343-8200
In an emergency situation these sources will quickly sell out so plan ahead.

How much do we need to take?

 Predicted Thyroid gland exposure (cGy)KI dose (mg)     Number or fraction of 130 mg tablets Number or fraction of 65 mg tablets Milliliters (mL) of oral solution, 65 mg/mL
Adults over
40 years
> 500 130 1 2 2 mL
Adults over
18 through 40 years
> 10 1301 22 mL
Pregnant or
Lactating Women
> 5 1301 22 mL
Adolescents,
12 through
18 years*

> 5

65½11 mL
Children over
3 years through 12 years
> 5 65 ½1 1 mL
Children 1
month through 3 years
> 5 32 Use KI oral solution** ½ 0.5 mL
Infants birth through 1
month
> 5 16 Use KI oral solution** Use KI oral solution** 0.25 mL
*     Adolescents approaching adult size (> 150 lbs) should receive the full adult dose (130 mg)
**   Potassium iodide oral solution is supplied in 1 oz (30 mL) bottles with a dropper marked for 1, 0.5, and 0.25 mL dosing.  each mL contains 65 mg potassium iodide.

Note: cGy is an abbreviation of "centigray per hour" which is a unit of measurement for tha amount of radiation absorbed. (one centigray equals one rad).

Side effects of Potassium Iodide

Thyroidal side effects of KI at recommended doses rarely occur in iodine-sufficient populations such as the U.S.A. The risk of thyroidal side effects is generally related to dose and to the presence of underlying thyroid disease (e.g., goiter, thyroiditis, Graves'). As a general rule, the risks of KI are far outweighed by the benefits with regard to prevention of thyroid cancer in susceptible individuals.

There are some reports that treatment with potassium iodide caused swelling of the parotid gland (one of the three glands which secrete saliva), due to its stimulatory effects on saliva production. (Source: McCance; Huether. "Pathophysiology: The biological basis for disease in Adults and Children". 5th Edition. Elsievier Publishing)

Taking potassium iodide (KI) to prevent thyroid cancer during a nuclear emergency may produce the following side effects: acne, loss of appetite, or upset stomach (especially during the first several days, as the body adjusts to the medication).

Although rare, more severe side effects are possible, which require notification of treatment by a physician: fever, weakness, unusual tiredness, swelling in the neck or throat, mouth sores, a metallic taste in the mouth, skin rash, nausea, vomiting, stomach pains, irregular heartbeat, numbness or tingling of the hands or feet.

Potassium iodide (KI) is a mild irritant so you may want to wear gloves. Chronic overexposure can have adverse effects on the thyroid. Potassium iodide is a possible teratogen or cause of biological growth deformities.

Do I need a prescription for KI?

No, potassium iodide is available over-the-counter (OTC) and no prescription is necessary. However, if you have any health concerns or questions, you should check with your doctor.

Who should not take potassium iodide (KI)?

Those with a known sensitivity to iodine should avoid KI, as should those with dermatitis herpetiformis and hypocomplementemic vasculitis. These are extremely rare conditions associated with an increased risk of iodine hypersensitivity. Individuals with Graves' disease, multinodular goiter, and autoimmune thyroiditis should be treated with caution, especially if dosing extends beyond a few days.

Notes on Potassium Iodide

The potassium iodide in iodized salt (table salt) will not provide sufficient protection because 80 tablespoons would be needed to equal one tablet of potassium iodide.

Of all the fallout products, radioactive iodide ( 131I ) is one of the most common and is particularly dangerous to the thyroid gland because it is known to lead to thyroid cancer.

Radioactive iodine has a half-life of just over 8 days (8.0197). This means that the amount of radiation given off by radioactive iodide decreases by half every eight days. Source: Nuclear Safety Commission [safety measures for nuclear facilities] revised August 2010.

Nature's warning system: Consider growing Spiderwort. This plant is Nature's gieger counter. Spiderwort normally has very dark purple flowers but when they are exposed to radiation or near an area where radiation is high, the flowers turn pink. Planting these somewhere in your yard where you can see them from a window would be one way to monitor excess radiation.

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Date: 3/16/2016
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This consumer advocate website is protected by copyright 2011 Askdocweb, Inc. All Rights Reserved. This is a layman's report on Potassium Iodide and is not intended to replace discussions with a health care provider. Do not use the information on this forum as a substitute for your doctor's advice. Always consult your doctor before taking any drug and follow your doctor's directions. Source material: Food and Drug Administration, Medline, Physician's Desk Reference, and the largest community of people in the world, those who are concerned about side effects and healthcare.
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