04:24 pm
March 14, 2011
Children in Kawamata, Japan, take potassium iodide on Monday to protect against thyroid cancer after being evacuated from the vicinity of the Fukushima Daiichi Nuclear Power Plant.
![]()
Asahi Shimbun via Getty Images
Children in Kawamata, Japan, take potassium iodide on Monday to protect against thyroid cancer after being evacuated from the vicinity of the Fukushima Daiichi Nuclear Power Plant.
Just in case, Japan has distributed a whole bunch of potassium iodide to evacuation centers near the troubled Fukushima Daiichi and Fukushima Daini nuclear power plants.
The International Atomic Energy Agency said in a statement that 230,000 units (the stuff comes in tablets and as a liquid) are at the ready.
Why is that important? Well, one of the substances that can be released in a nuclear accident is radioactive iodine (I-131, if you're interested in the details). And some radioactive iodine has already been detected by Japanese authorities.
You need a little bit of iodine so the thyroid gland in your neck can make hormones to regulate your metabolism. But your body can't tell the difference between the normal iodine found in salt or seafood and the radioactive variety from a wayward nuclear power station.
So the thyroid, which concentrates iodine, can get a hefty dose of radiation from I-131 that makes it into the food supply after a nuclear incident. The radiation can hike the risk for subsequent thyroid cancer.
"Iodine is the building block for thyroid hormone," Nestor Rigual, a head and neck surgeon at Roswell Park Cancer Center explains to Shots. "The thyroid tissue has a very specific and strong affinity for absorbing iodine." Potassium tablets can saturate the gland and crowd out the radioactive iodine in a chemcial competition, he says. "In that way, the radioactive iodine doesn't have as high a chance of damaging the gland."
Iodine tablets can prevent the absorption of radioactive iodine for up to 24 hours, according to the Centers for Disease Control and Prevention. The amount of iodine you can get from iodized salt or your regular diet isn't enough to protect you.
Young children and fetuses are most vulnerable to radioactive iodine, the CDC says. Older people aren't at as much risk, and CDC says people older than 40 shouldn't take preventive iodine supplements "unless a very large dose of radioactive iodine is expected" and public health officials recommend it.
Roswell Park's Dr. Rigual says even relatively modest doses of radiation can increase the risk that a person will develop thyroid cancer at some point in life. There's a delay between exposure and cancer that can run 10 to 20 years, he says.
The supplemental iodine isn't a complete guarantee of protection. A lag in taking the pills after exposure can reduce the supplement's effectiveness, for instance. Also, the iodine pills only offer work against radioactive iodine — not other radioactive elements, such as cesium, which has also been detected.
And some people allergic to iodine or with certain skin conditions may not be able to tolerate the supplements, the CDC says.
Separately, ProPublica revisits the Bush administration's controversial decision in 2008 to scrap plans to distribute potassium iodide to people in a zone extending between 10 and 20 miles from the site of a nuclear incident. A White Memo says there are more effective responses, including evacuation, for people that far out. The government policy, according to the memo, would still support the use of the potassium pills in an emergency zone within 10 miles of radioactive trouble.
March 14, 2011
Children in Kawamata, Japan, take potassium iodide on Monday to protect against thyroid cancer after being evacuated from the vicinity of the Fukushima Daiichi Nuclear Power Plant.
Children in Kawamata, Japan, take potassium iodide on Monday to protect against thyroid cancer after being evacuated from the vicinity of the Fukushima Daiichi Nuclear Power Plant.
Just in case, Japan has distributed a whole bunch of potassium iodide to evacuation centers near the troubled Fukushima Daiichi and Fukushima Daini nuclear power plants.
The International Atomic Energy Agency said in a statement that 230,000 units (the stuff comes in tablets and as a liquid) are at the ready.
Why is that important? Well, one of the substances that can be released in a nuclear accident is radioactive iodine (I-131, if you're interested in the details). And some radioactive iodine has already been detected by Japanese authorities.
You need a little bit of iodine so the thyroid gland in your neck can make hormones to regulate your metabolism. But your body can't tell the difference between the normal iodine found in salt or seafood and the radioactive variety from a wayward nuclear power station.
So the thyroid, which concentrates iodine, can get a hefty dose of radiation from I-131 that makes it into the food supply after a nuclear incident. The radiation can hike the risk for subsequent thyroid cancer.
"Iodine is the building block for thyroid hormone," Nestor Rigual, a head and neck surgeon at Roswell Park Cancer Center explains to Shots. "The thyroid tissue has a very specific and strong affinity for absorbing iodine." Potassium tablets can saturate the gland and crowd out the radioactive iodine in a chemcial competition, he says. "In that way, the radioactive iodine doesn't have as high a chance of damaging the gland."
Iodine tablets can prevent the absorption of radioactive iodine for up to 24 hours, according to the Centers for Disease Control and Prevention. The amount of iodine you can get from iodized salt or your regular diet isn't enough to protect you.
Young children and fetuses are most vulnerable to radioactive iodine, the CDC says. Older people aren't at as much risk, and CDC says people older than 40 shouldn't take preventive iodine supplements "unless a very large dose of radioactive iodine is expected" and public health officials recommend it.
Roswell Park's Dr. Rigual says even relatively modest doses of radiation can increase the risk that a person will develop thyroid cancer at some point in life. There's a delay between exposure and cancer that can run 10 to 20 years, he says.
The supplemental iodine isn't a complete guarantee of protection. A lag in taking the pills after exposure can reduce the supplement's effectiveness, for instance. Also, the iodine pills only offer work against radioactive iodine — not other radioactive elements, such as cesium, which has also been detected.
And some people allergic to iodine or with certain skin conditions may not be able to tolerate the supplements, the CDC says.
Separately, ProPublica revisits the Bush administration's controversial decision in 2008 to scrap plans to distribute potassium iodide to people in a zone extending between 10 and 20 miles from the site of a nuclear incident. A White Memo says there are more effective responses, including evacuation, for people that far out. The government policy, according to the memo, would still support the use of the potassium pills in an emergency zone within 10 miles of radioactive trouble.
----------------------------------------------------
CDC (Centers for Disease Control and Prevention in the U.S.)on Potassium Iodide (KI)
http://www.bt.cdc.gov/radiation/ki.asp
What is Potassium Iodide (KI)?
Potassium iodide (also called KI) is a salt of stable (not radioactive) iodine. Stable iodine is an important chemical needed by the body to make thyroid hormones. Most of the stable iodine in our bodies comes from the food we eat. KI is stable iodine in a medicine form. This fact sheet from the Centers for Disease Control and Prevention (CDC) gives you some basic information about KI. It explains what you should think about before you or a family member takes KI.
What does KI do?
Following a radiological or nuclear event, radioactive iodine may be released into the air and then be breathed into the lungs. Radioactive iodine may also contaminate the local food supply and get into the body through food or through drink. When radioactive materials get into the body through breathing, eating, or drinking, we say that “internal contamination” has occurred. In the case of internal contamination with radioactive iodine, the thyroid gland quickly absorbs this chemical. Radioactive iodine absorbed by the thyroid can then injure the gland. Because non-radioactive KI acts to block radioactive iodine from being taken into the thyroid gland, it can help protect this gland from injury.
What KI cannot do
Knowing what KI cannot do is also important. KI cannot prevent radioactive iodine from entering the body. KI canprotect only the thyroid from radioactive iodine, not other parts of the body. KI cannot reverse the health effects caused by radioactive iodine once damage to the thyroid has occurred. KI cannotprotect the body from radioactive elements other than radioactive iodine—if radioactive iodine is not present, taking KI is not protective.
How does KI work?
The thyroid gland cannot tell the difference between stable and radioactive iodine and will absorb both. KI works by blocking 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.
Iodized table salt also contains iodine; iodized table salt contains enough iodine to keep most people healthy under normal conditions. However, table salt does not contain enough iodine to block radioactive iodine from getting into your thyroid gland. You should not use table salt as a substitute for KI.
How well does KI work?
Knowing that KI may not give a person 100% protection against radioactive iodine is important. How well KI blocks radioactive iodine depends on
- how much time passes between contamination with radioactive iodine and the taking of KI (the sooner a person takes KI, the better),
- how fast KI is absorbed into the blood, and
- the total amount of radioactive iodine to which a person is exposed.
Who should take KI?
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 stores of iodine in their thyroid are also at risk of thyroid injury.
Infants (including breast-fed infants): Infants need to be given the recommended dosage of KI for babies (see How much KI should I take?). The amount of KI that gets into breast milk is not enough to protect breast-fed infants from exposure to radioactive iodine. The proper dose of KI given to a nursing infant will help protect it from radioactive iodine that it breathes in or drinks in breast milk.
Children: The United States Food and Drug Administration (FDA) recommends that all children internally contaminated with (or likely to be internally contaminated with) radioactive iodine take KI, unless they have known allergies to iodine. Children from newborn to 18 years of age are the most sensitive to the potentially harmful effects of radioactive iodine.
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. 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 to protect the growing fetus. However, 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 if they have been internally contaminated with (or are likely to be internally contaminated with) radioactive iodine. Because radioactive iodine quickly gets into breast milk, CDC recommends that women internally contaminated with (or are likely to be internally contaminated with) radioactive iodine stop breastfeeding and feed their child baby formula or other food if it is available. If breast milk is the only food available for an infant, nursing should continue.
Adults: Adults older than 40 years should not take KI 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. They also have a greater chance of having allergic reactions to KI.
When should I take KI?
After a radiologic or nuclear event, local public health or emergency management officials will tell the public if KI or other protective actions are needed. For example, public health officials may advise you to remain in your home, school, or place of work (this is known as “shelter-in-place”) or to evacuate. You may also be told not to eat some foods and not to drink some beverages until a safe supply can be brought in from outside the affected area. Following the instructions given to you by these authorities can lower the amount of radioactive iodine that enters your body and lower the risk of serious injury to your thyroid gland.
How much KI should I take?
The FDA has approved two different forms of KI—tablets and liquid—that people can take by mouth after a nuclear radiation emergency. Tablets come in two strengths, 130 milligram (mg) and 65 mg. The tablets are scored so they may be cut into smaller pieces for lower doses. Each milliliter (mL) of the oral liquid solution contains 65 mg of KI.
According to the FDA, the following doses are appropriate to take after internal contamination with (or likely internal contamination with) radioactive iodine:
- 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.
- 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.
- 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.
- 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.
How often should I take KI?
A single dose of KI protects the thyroid gland for 24 hours. A one-time dose at the levels recommended in this fact sheet is usually all that is needed to protect the thyroid gland. In some cases, radioactive iodine might be in the environment for more than 24 hours. If that happens, local emergency management or public health officials may tell you to take one dose of KI every 24 hours for a few days. You should do this only on the advice of emergency management officials, public health officials, or your doctor. Avoid repeat dosing with KI for pregnant and breastfeeding women and newborn infants. Those individuals may need to be evacuated until levels of radioactive iodine in the environment fall.
Taking a higher dose of KI, or taking KI more often than recommended, does not offer more protection and can cause severe illness or death.
Medical conditions that may make it harmful to take KI
Taking KI may be harmful for some people because of the high levels of iodine in this medicine. You should not take KI if
• you know you are allergic to iodine (If you are unsure about this, consult your doctor. A seafood or shellfish allergy does not necessarily mean that you are allergic to iodine.) or
• you have certain skin disorders (such as dermatitis herpetiformis or urticaria vasculitis).
People with thyroid disease (for example, multinodular goiter, Graves’ disease, or autoimmune thyroiditis) may be treated with KI. This should happen under careful supervision of a doctor, especially if dosing lasts for more than a few days.
In all cases, talk to your doctor if you are not sure whether to take KI.
What are the possible risks and side effects of KI?
When public health or emergency management officials tell the public to take KI following a radiologic or nuclear event, the benefits of taking this drug outweigh the risks. This is true for all age groups. Some general side effects caused by KI may include intestinal upset, allergic reactions (possibly severe), rashes, and inflammation of the salivary glands.
When taken as recommended, KI causes only rare adverse health effects that specifically involve the thyroid gland. In general, you are more likely to have an adverse health effect involving the thyroid gland if you
- take a higher than recommended dose of KI,
- take the drug for several days, or
- have pre-existing thyroid disease.
Newborn infants (less than 1 month old) who receive more than one dose of KI are at particular 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 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?
KI is available without a prescription. You should talk to your pharmacist to get KI and for directions about how to take it correctly. Your pharmacist can sell you KI brands that have been approved by the FDA.
Other Sources of Information
--------------------------------------------------------------------
FDA on requently Asked Questions on Potassium Iodide (KI)
http://www.fda.gov/Drugs/EmergencyPreparedness/BioterrorismandDrugPreparedness/ucm072265.htm
In December 2001, the Food and Drug Administration (FDA) issued a final Guidance on Potassium Iodide as a Thyroid Blocking Agent in Radiation Emergencies1. The objective of the document is to provide guidance to other Federal agencies, including the Environmental Protection Agency (EPA) and the Nuclear Regulatory Commission (NRC), and to state and local governments regarding the safe and effective use of potassium iodide (KI) as an adjunct to other public health protective measures in the event that radioactive iodine is released into the environment. The adoption and implementation of the recommendations are at the discretion of the state and local governments responsible for developing regional emergency-response plans related to radiation emergencies. The recommendations in the guidance address KI dosage and the projected radiation exposure at which the drug should be used. This guidance updates FDA’s 1982 recommendations.
- What does potassium iodide (KI) do?
- Can potassium iodide ( KI) be used to protect against radiation from bombs other than radioactive iodine?
- Who really needs to take potassium iodide (KI) after a nuclear radiation release?
- What potassium iodide (KI) products are currently available?
- How are these products available?
- What dosages of potassium iodide ( KI) should be taken for specific exposure levels?
- How long should potassium iodide ( KI) be taken?
- Who should not take potassium iodide ( KI) or have restricted use?
- What are the possible risks and side effects of taking potassium iodide ( KI)?
- Should I check with my doctor first?
- As a doctor, should I be recommending potassium iodide ( KI) for my patients who request it?
- Should I go out and buy potassium iodide ( KI) to keep on hand?
- How do I know that potassium iodide ( KI) will be available in case of an emergency?
1. What does potassium iodide (KI) do?
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.
2. Can potassium iodide (KI) be used to protect against radiation from bombs other than radioactive iodine?
Potassium iodide ( KI) works only to prevent the thyroid from uptaking radioactive iodine. It is not a general radioprotective agent.
3. Who really needs to take potassium iodide (KI) after a nuclear radiation release?
The FDA guidance prioritizes groups based on age, which primarily determines risk for radioiodine-induced thyroid cancer. Those at highest risk are infants and children, as well as pregnant and nursing females, and the recommendation is to treat them at the lowest threshold (with respect to predicted radioactive dose to the thyroid). Anyone over age 18 and up to age 40 should be treated at a slightly higher threshold. Finally, anyone 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).
4. What potassium iodide (KI) products are currently available?
As of January 2005, Iosat, ThyroSafe, and ThyroShield are FDA approved KI products. You can find out more about these products at Drugs@FDA2. Please be aware that only the KI products approved by FDA may be legally marketed in the United States.
5. How are these products available?
In addition to distributing to state, local and federal agencies, Anbex, Inc., has made Iosat Tablets (130 mg) available to the general public via the Internet. For further information on KI products, you can contact these companies as noted below:
- Anbex, Inc. for Iosat Tablets (130 mg) at 212-580-2810 (M-F 9am-5pm), at 1-866-463-6754 (other times), or http://www.anbex.com3
- Recipe for ThyroSafe Tablets (65 mg) at 1-866-849-7672 or http://www.thyrosafe.com/recip.html4
- Fleming & Company, Pharmaceuticals for ThyroShield Solution at 636-343-8200 or http://www.flemingcompany.com5 or http://www.thyroshield.com6
6. What dosages of potassium iodide (KI) should be taken for specific exposure levels?
Exposures greater than 5 cGy:
Birth through 1 mo. - 16 mg.
1 mo. through 3 yrs. - 32 mg.
3 yrs through 18 yrs. - 65 mg. (Adolescents>150 pounds should take adult dose.)
Exposures greater than 10 cGy:
18 yrs through 40 yrs. - 130 mg
Exposures greater than 500 cGy:
Adults over 40 yrs - 130 mg.
7. How long should potassium iodide (KI) be taken?
Since KI protects for approximately 24 hours, it should be dosed daily until the risk no longer exists. Priority with regard to evacuation and sheltering should be given to pregnant females and neonates because of the potential for KI to suppress thyroid function in the fetus and neonate. Unless other protective measures are not available, we do not recommend repeat dosing in pregnant females and neonates.
8. Who should not take potassium iodide (KI) or have restricted use?
Persons with known iodine sensitivity should avoid KI, as should individuals with dermatitis herpetiformis and hypocomplementemic vasculitis, extremely rare conditions associated with an increased risk of iodine hypersensitivity. Individuals with multinodular goiter, Graves' disease, and autoimmune thyroiditis should be treated with caution -- especially if dosing extends beyond a few days.
9. What are the possible risks and side effects of taking potassium iodide (KI)?
Thyroidal side effects of KI at recommended doses rarely occur in iodine-sufficient populations such as the U.S. As a rule, the risk of thyroidal side effects is related to dose and to the presence of underlying thyroid disease (e.g., goiter, thyroiditis, Graves'). FDA recommends adherence to the Guidance on Potassium Iodide as a Thyroid Blocking Agent in Radiation Emergencies7 for intervention threshold and dose, though we recognize that the exigencies of any particular emergency situation may mandate deviations from those recommendations. With that in mind, it should be understood that as a general rule, the risks of KI are far outweighed by the benefits with regard to prevention of thyroid cancer in susceptible individuals.
10. Should I check with my doctor first?
Potassium iodide (KI) is available over-the-counter (OTC). However, if you have any health concerns or questions, you should check with your doctor.
11. As a doctor, should I be recommending potassium iodide (KI) for my patients who request it?
As with any drug, physicians should understand the risks and benefits of KI before recommending it or prescribing it to patients. We recommend that physicians read our guidance for more information. It is available on the FDA Drug Guidances8 web page, under procedural guidance #18. The FDA guidance discusses the rationale and methods of safe and effective use of KI in radiation emergencies. It specifically addresses threshold predicted thyroid radioiodine exposure for intervention and dosing by age group. The recommendations for intervention are based on categories of risk for thyroid cancer, with the young prioritized because of increased sensitivity to the carcinogenic effects of radioiodine.
12. Should I go out and buy potassium iodide (KI) to keep on hand?
KI works best if used within 3-4 hours of exposure. Although FDA has not made specific recommendations for individual purchase or use of KI, the Nuclear Regulatory Commission has contracted to purchase KI for states with nuclear reactors and states that have population within the 10-mile emergency planning zone, e.g., Delaware or West Virginia.
13. How do I know that potassium iodide (KI) will be available in case of an emergency?
FDA will continue to work with interested pharmaceutical manufacturers to assure that high quality, safe, and effective KI products are available for purchase by consumers, by state and local authorities, and by federal government agencies electing to do so.
| 編輯 | 刪除