Manouchehr Saljoughian, PharmD, PhDDepartment that Pharmacy, Alta Bates Summit medical Center, Berkeley, California


US Pharm.

You are watching: How much potassium iodide to protect from radiation

2011;36(6):HS-25-HS-28.

Potassium iodide (KI) is an inorganic compound the is easily accessible from three manufacturers under various brand names as an antidote come radiation exposure. Native a chemistry point of view, it is made from potassium hydroxide and also iodine, and it is the most produced iodide link in the world. The is wanted over salt iodide salt due to the fact that it is much less hygroscopic and easier to handle; the is an odorless and stable white crystalline powder. Among its other applications, the is supplied in the photography market to form silver iodide and in chemical laboratories as a resource of iodide in essential synthesis. KI is likewise used in biomedical study as a fluorescence quencher v its iodide ion. Upon expanded exposure come air, KI becomes yellow as a an outcome of the liberation the iodine, and tiny quantities the iodate might be formed as result of oxidation.1

Although KI has actually several medical and also nutritional applications, that most vital application is together an antidote to radiation. Recently, KI has been in high need in the joined States as result of the warning about remote radiation exposure native the recent Japanese nuclear tree radioactive releases.2 For medical purposes, a saturated systems of KI is provided to law lung congestion (as one expectorant) and sporotrichosis (a fungal infection) and as an antiseptic in sick throats.

KI"s worth as a radiation protective or antithyroid agent was demonstrated at the time of the Chernobyl nuclear accident when Russian authorities dispersed KI in a 30-km zone approximately the plant. The purpose was to defend residents indigenous the radiation iodine, the many abundant and also highly carcinogenic material found in nuclear reactors, that had actually been exit by the damaged reactors.2,3

KI is offered as 130-mg tablets for emergency purposes. That may additionally be administered together a viscous saturated solution of potassium iodide (SSKI). This formulation offers 250 mg the iodide every each five drops. Follow to the USP, each two drops the this solution (containing 100 mg that iodide) have actually the same amount of iodide as a 130-mg tablet of KI (130 mg = 100 mg iodide).2

Thyroid security After atom Accidents/Events

KI was authorized by the FDA in 1982 to protect the thyroid gland from radioactive iodine released accidentally native nuclear strength plants or during a nuclear attack. In these events, plenty of radionuclide products may be discharged come the atmosphere. Of these products, I131 is among the most common, and also it is particularly dangerous come the thyroid gland.1

By saturating the body v a source of secure iodide such as KI before exposure, inhaled or ingested I131 will be excreted indigenous the body, and also as a result, radioiodine absorb by the thyroid gland will certainly not take it place. The protective impact of KI lasts about 24 hours. For optimal prophylaxis, KI have to be dosed day-to-day until the threat of far-ranging exposure to radioiodine by either inhalation or sloop down no longer exists.

Doses that 130 mg KI provide 100 mg iodide, which is roughly 700 times better than the common nutritional require for iodine of 150 mcg (0.15 mg, as iodide) per day for an adult. The KI in iodized salt is poor for this use, as 80 tablespoons would be essential to same one tablet. Watch TABLE 1 for the encourage FDA dosing regimen for humans.2 KI cannot protect against any other causes of radiation poisoning or against radionuclide other than radioisotopes the iodine.

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Dosing Equivalency: For defense of the thyroid versus I131 contamination, the convenient traditional 130-mg KI pill is used, if available. As noted, the tantamount two drops of SSKI might be used for this purpose if the pills room not available.

Protecting Effect: When KI is administered at the same time with radiation exposure, the protective result is about 97%. KI given 12 and also 24 hours prior to exposure returns a 90% and 70% security effect, respectively. However, KI administered 1 and 3 hrs after exposure outcomes in one 85% and also 50% security effect, respectively. KI administered an ext than 6 hrs after exposure is believed to have a negligible security effect.4

It was reported on in march 16, 2011, the KI tablet computers were provided prophylactically to U.S. Naval wait crewmembers flying within 70 miles of the Fukushima Daiichi nuclear plant damaged in the substantial Japanese earthquake (8.9/9.0 magnitude) and also ensuing tsunami on march 11, 2011. The measures were viewed as precautions, and the Pentagon stated no U.S. Forces have presented signs that radiation poisoning. By march 20, the U.S. Marine had additionally instructed personnel coming in ~ 100 miles of the reactor to take the pills as a preventative measure.5,6

Radionuclide Iodine in nuclear Medicine

As opposed to the harmful release of I131 in atom disasters, an iodide radionuclide in different radiopharmaceutical forms (and not necessarily as KI) is offered in nuclear medication for diagnostic and therapeutic purposes.7 The thyroid gland absorbs nearly all of the iodine in the blood. When enough of the medical kind of I131 is taken into the thyroid, the can ruin the thyroid gland and any various other thyroid cell (including cancer cells) the take up iodine, with small effect on the remainder of the body. The radiation iodine is usually provided as a capsule or liquid. This treatment have the right to be provided to destroy any type of thyroid organization not eliminated by surgical treatment or to treat thyroid cancer that has spread come lymph nodes and other parts of the body.

Radioactive iodine therapy has been presented to enhance the survival price of patients through papillary or follicular thyroid cancer (differentiated thyroid cancer) that has spread come the neck or other body parts, and this therapy is now the standard practice in such cases. Radioactive iodine therapy cannot be provided to act undifferentiated and also medullary thyroid carcinomas due to the fact that these types of cancer execute not take up iodine.

Although this knowingly hypothyroidism is temporary, the often causes symptoms such as tiredness, depression, weight gain, sleepiness, constipation, muscle aches, and also reduced concentration. An injectable form of thyrotropin is now easily accessible that have the right to increase a patient"s thyroid-stimulating hormone level to get rid of some of this symptoms.

Many medical specialists recommend that ladies avoid coming to be pregnant for 6 months to a year after ~ treatment. No ill impacts have been noted in children whose parents received radioactive iodine in the past.

Other clinical Applications

There are a variety of labeled and also unlabeled clinical applications because that KI.

Preoperative Thyroidectomy: KI in sheep of 50 come 250 mg (1-5 drops SSKI) 3 times/day is administered because that 10 days prior to thyroid surgery.8

Thyrotoxic Crisis: SSKI can be an emergency therapy for hyperthyroidism or thyroid storm in sheep of 250 mg (5 drops SSKI) every 6 hours. High amounts of iodide in the interim suppress secretion of thyroxine from the thyroid gland.8

Expectorant: KI is provided for the symptomatic therapy of chronic pulmonary diseases complex by mucus. Iodide options made from a few drops of SSKI added to drinks have been supplied as risk to increase the water contents of respiratory secretions and encourage reliable coughing.

Sporotrichosis (Cutaneous, Lymphocutaneous): Oral: Initially, five drops (SSKI) three times/day; increase to 40 to 50 fall (SSKI) three times/day together tolerated till 2 to 4 weeks ~ lesions have actually resolved (usual term 3-6 months). KI has actually been provided in symptomatic treatment of erythema nodosum because that persistent lesions whose reason remains unknown. The has likewise been offered in cases of erythema nodosum linked with Crohn"s disease.9

Nutritional Applications

As a nutritional supplement, KI is the most common additive come table salt to protect against iodine deficiency in populaces that consume small seafood. Because KI is gradually oxidized from waiting exposure, that is replaced in specific products by potassium iodate, which is not shed by oxidation.10

None that the accessible pharmaceutical formulations (SSKI or KI tablets) are intended for use as nutritional supplements, as result of the an extremely high concentration that iodine. The nutritional requirement for iodine in humans is just 150 mcg (0.15 mg) that iodide every day.

There are herbal sources that iodide because that nutritional purposes. Kelp is a natural KI source. One-quarter cup the kelp supplies just 9 calories and also 276.7% of everyday iodine needs. The iodide contents is about 89 mcg/g in oriental varieties. Another natural resource of iodide is seaweed. Dried, unrinsed seaweed (3-5 g) will administer the recommended everyday allowance of 100 to 150 mcg the iodide for nutritional purposes. Other organic sources room seafood, asparagus, turnip greens, spinach, and also Swiss chard.10

Adverse Reactions

There have been part reports the KI treatment resulting in swelling the the parotid gland (one that the 3 glands that secrete saliva), due to the fact that of the stimulatory effects on saliva production. Various other reported disadvantage reactions reported encompass irregular heartbeat, skin rash, diarrhea, metallic taste, stomach upset, share pain, numbness, and also tingling.

Chronic iodine poisoning from an extensive treatment or high sheep can reason iodism, hypersensitivity reactions the are materialized as angioedema, cutaneous and also mucosal hemorrhage, and also serum sickness-like symptoms.4

Drug Interactions

Potassium salt may improve the hyperkalemic result of angiotensin-converting enzyme inhibitors, angiotensin II receptor blockers, and potassium-sparing diuretics. KI may improve the hypothyroid result of lithium. Antithyroid agents may diminish the anticoagulant result of vitamin K antagonists. In every these cases, therapy should be carefully monitored, and also dosing adjustments should be made.4

Pregnancy/Lactation Considerations

Iodide the cross the placenta and, therefore, may reason hypothyroidism and also goiter in the fetus or newborn. The usage of KI is contraindicated as an expectorant during pregnancy by the American Academy the Pediatrics (AAP). Its use for protection against thyroid cancer secondary to radioactive iodine exposure is thought about acceptable based top top risk-to-benefit ratio, dose, and also duration. The AAP recommends staying clear of breast-feeding following radioactive iodine exposure. That may cause skin rashes in a parenting infant.4

Conclusions

KI cannot prevent radioactive iodine native entering the body. KI can safeguard only the thyroid from radioactive iodine, however not other parts that the body. In addition, KI cannot turning back the health effects caused by radiation iodine once damages to the thyroid has actually happened. KI cannot protect the body from radioactive facets other than radioactive iodine; if radioactive iodine is no present, taking KI is no protective.

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Three service providers (Anbex Inc., Fleming Pharmaceuticals, and Recipharm AB) currently have FDA approval for manufacturing and testing the KI. These companies offer IOSAT (130 mg), Thyroshield (65 mg), and Thyro-Safe (65 mg), respectively.

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