Potassium iodide
Overview
Potassium iodide is an inorganic compound
Inorganic compound
Inorganic compounds have traditionally been considered to be of inanimate, non-biological origin. In contrast, organic compounds have an explicit biological origin. However, over the past century, the classification of inorganic vs organic compounds has become less important to scientists,...

 with the chemical formula
Chemical formula
A chemical formula or molecular formula is a way of expressing information about the atoms that constitute a particular chemical compound....

 K
Potassium
Potassium is the chemical element with the symbol K and atomic number 19. Elemental potassium is a soft silvery-white alkali metal that oxidizes rapidly in air and is very reactive with water, generating sufficient heat to ignite the hydrogen emitted in the reaction.Potassium and sodium are...

I
Iodide
An iodide ion is the ion I−. Compounds with iodine in formal oxidation state −1 are called iodides. This page is for the iodide ion and its salts. For information on organoiodides, see organohalides. In everyday life, iodide is most commonly encountered as a component of iodized salt,...

. This white salt is the most commercially significant iodide compound, with approximately 37,000 tons produced in 1985. It is less hygroscopic (absorbs water less readily) than sodium iodide
Sodium iodide
Sodium iodide is a white, crystalline salt with chemical formula NaI used in radiation detection, treatment of iodine deficiency, and as a reactant in the Finkelstein reaction.-Uses:Sodium iodide is commonly used to treat and prevent iodine deficiency....

, making it easier to work with. Aged and impure samples are yellow because of aerial oxidation of the iodide
Iodide
An iodide ion is the ion I−. Compounds with iodine in formal oxidation state −1 are called iodides. This page is for the iodide ion and its salts. For information on organoiodides, see organohalides. In everyday life, iodide is most commonly encountered as a component of iodized salt,...

 to elemental iodine
Iodine
Iodine is a chemical element with the symbol I and atomic number 53. The name is pronounced , , or . The name is from the , meaning violet or purple, due to the color of elemental iodine vapor....

.
4 KI + 2 CO2 + O2 → 2 K2CO3 + 2 I2


Potassium iodide is medicinally supplied in 130 mg tablets for emergency purposes.
Encyclopedia
Potassium iodide is an inorganic compound
Inorganic compound
Inorganic compounds have traditionally been considered to be of inanimate, non-biological origin. In contrast, organic compounds have an explicit biological origin. However, over the past century, the classification of inorganic vs organic compounds has become less important to scientists,...

 with the chemical formula
Chemical formula
A chemical formula or molecular formula is a way of expressing information about the atoms that constitute a particular chemical compound....

 K
Potassium
Potassium is the chemical element with the symbol K and atomic number 19. Elemental potassium is a soft silvery-white alkali metal that oxidizes rapidly in air and is very reactive with water, generating sufficient heat to ignite the hydrogen emitted in the reaction.Potassium and sodium are...

I
Iodide
An iodide ion is the ion I−. Compounds with iodine in formal oxidation state −1 are called iodides. This page is for the iodide ion and its salts. For information on organoiodides, see organohalides. In everyday life, iodide is most commonly encountered as a component of iodized salt,...

. This white salt is the most commercially significant iodide compound, with approximately 37,000 tons produced in 1985. It is less hygroscopic (absorbs water less readily) than sodium iodide
Sodium iodide
Sodium iodide is a white, crystalline salt with chemical formula NaI used in radiation detection, treatment of iodine deficiency, and as a reactant in the Finkelstein reaction.-Uses:Sodium iodide is commonly used to treat and prevent iodine deficiency....

, making it easier to work with. Aged and impure samples are yellow because of aerial oxidation of the iodide
Iodide
An iodide ion is the ion I−. Compounds with iodine in formal oxidation state −1 are called iodides. This page is for the iodide ion and its salts. For information on organoiodides, see organohalides. In everyday life, iodide is most commonly encountered as a component of iodized salt,...

 to elemental iodine
Iodine
Iodine is a chemical element with the symbol I and atomic number 53. The name is pronounced , , or . The name is from the , meaning violet or purple, due to the color of elemental iodine vapor....

.
4 KI + 2 CO2 + O2 → 2 K2CO3 + 2 I2


Potassium iodide is medicinally supplied in 130 mg tablets for emergency purposes. Potassium iodide may also be administered as a "saturated solution of potassium iodide" (SSKI) which in the U.S.P. generic formulation contains 1000 mg of KI per mL of solution. This represents 333 mg KI and about 250 mg iodide (I -) in a typical adult dose of 5 drops, assumed to be ⅓ mL. Because SSKI is a viscous liquid, it is normally assumed to contain 15 drops/milliliter, not 20 drops/milliliter as is often assumed for water. Thus, each drop of U.S.P. SSKI is assumed to contain about 50 mg iodine as iodide, I -. Thus, two (2) drops of U.S.P. SSKI solution is equivalent to one 130 mg KI tablet (100 mg iodide).

SSKI can also be prepared by truly saturating water with KI. This preparation can be made without a measuring scale. Since the solubility of KI in water at room temperature is about 1.40 to 1.48 grams per mL pure water, and the resulting solution has a density of about 1.72 g/mL, this process also results in a final concentration) of KI of about 1000 mg KI per mL of saturated KI solution, and also contains essentially the same concentration of iodide per drop as does the U.S.P. formulation.

Neither SSKI or KI tablets are used as nutritional supplements, since the nutritional requirement for iodine is only 150 micrograms or 0.15 mg of iodide per day. Thus, a drop of SSKI provides 50/0.15 = 333 times the daily iodine requirement, and a standard KI tablet provides twice this much.

Kelp
Kelp
Kelps are large seaweeds belonging to the brown algae in the order Laminariales. There are about 30 different genera....

 is a natural KI source. The iodide content can range from 89 µg
Microgram
In the metric system, a microgram is a unit of mass equal to one millionth of a gram , or 1/1000 of a milligram. It is one of the smallest units of mass commonly used...

/g to 8165 µg/g in Asian varieties, making prepared foods content difficult to estimate. Eating 3-5 grams of most dried, unrinsed seaweeds will provide the 100-150 micrograms iodide recommended daily allowance for nutritional purposes.

Structure, production, properties

Potassium iodide is ion
Ion
An ion is an atom or molecule in which the total number of electrons is not equal to the total number of protons, giving it a net positive or negative electrical charge. The name was given by physicist Michael Faraday for the substances that allow a current to pass between electrodes in a...

ic, K+I. It crystallises in the sodium chloride
Sodium chloride
Sodium chloride, also known as salt, common salt, table salt or halite, is an inorganic compound with the formula NaCl. Sodium chloride is the salt most responsible for the salinity of the ocean and of the extracellular fluid of many multicellular organisms...

 structure. It is produced industrially by treating KOH with iodine.

Inorganic chemistry

Since the iodide
Iodide
An iodide ion is the ion I−. Compounds with iodine in formal oxidation state −1 are called iodides. This page is for the iodide ion and its salts. For information on organoiodides, see organohalides. In everyday life, iodide is most commonly encountered as a component of iodized salt,...

 ion is a mild reducing agent
Redox
Redox reactions describe all chemical reactions in which atoms have their oxidation state changed....

, I is easily oxidised to I2
Iodine
Iodine is a chemical element with the symbol I and atomic number 53. The name is pronounced , , or . The name is from the , meaning violet or purple, due to the color of elemental iodine vapor....

 by powerful oxidising agents
Redox
Redox reactions describe all chemical reactions in which atoms have their oxidation state changed....

 such as chlorine
Chlorine
Chlorine is the chemical element with atomic number 17 and symbol Cl. It is the second lightest halogen, found in the periodic table in group 17. The element forms diatomic molecules under standard conditions, called dichlorine...

:
2 KI(aq) + Cl2(aq) → 2 KCl
Potassium chloride
The chemical compound potassium chloride is a metal halide salt composed of potassium and chlorine. In its pure state, it is odorless and has a white or colorless vitreous crystal appearance, with a crystal structure that cleaves easily in three directions. Potassium chloride crystals are...

  + I2(aq)

This reaction is employed in the isolation of iodine from natural sources. Air will oxidize iodide, as evidenced by the observation of a purple extract when aged samples of KI are rinsed with dichloromethane
Dichloromethane
Dichloromethane is an organic compound with the formula CH2Cl2. This colorless, volatile liquid with a moderately sweet aroma is widely used as a solvent. Although it is not miscible with water, it is miscible with many organic solvents...

. As formed under acidic conditions, hydroiodic acid (HI) is a stronger reducing agent.

Like other iodide salts, KI forms I3
Triiodide
In chemistry, triiodide can have several meanings. Triiodide primarily refers to the triiodide ion, I3−, a polyatomic anion composed of three iodine atoms. For some chemical compounds, triiodide indicates a salt of the named cation with the triiodide anion. Examples include sodium triiodide, ...

 when combined with elemental iodine
Iodine
Iodine is a chemical element with the symbol I and atomic number 53. The name is pronounced , , or . The name is from the , meaning violet or purple, due to the color of elemental iodine vapor....

.
KI(aq) + I2
Iodine
Iodine is a chemical element with the symbol I and atomic number 53. The name is pronounced , , or . The name is from the , meaning violet or purple, due to the color of elemental iodine vapor....

(s
Solid
Solid is one of the three classical states of matter . It is characterized by structural rigidity and resistance to changes of shape or volume. Unlike a liquid, a solid object does not flow to take on the shape of its container, nor does it expand to fill the entire volume available to it like a...

) → KI3(aq)

Unlike I2, I3 salts can be highly water-soluble. Through this reaction iodine
Iodine
Iodine is a chemical element with the symbol I and atomic number 53. The name is pronounced , , or . The name is from the , meaning violet or purple, due to the color of elemental iodine vapor....

 is used in redox
Redox
Redox reactions describe all chemical reactions in which atoms have their oxidation state changed....

 titration
Titration
Titration, also known as titrimetry, is a common laboratory method of quantitative chemical analysis that is used to determine the unknown concentration of an identified analyte. Because volume measurements play a key role in titration, it is also known as volumetric analysis. A reagent, called the...

s. Aqueous KI3, "Lugol's solution," are used as disinfectants and as etchants for gold surfaces.

Potassium iodide is the precursor to silver(I) iodide, which is used for high speed photographic film
Photographic film
Photographic film is a sheet of plastic coated with an emulsion containing light-sensitive silver halide salts with variable crystal sizes that determine the sensitivity, contrast and resolution of the film...

:
KI(aq) + AgNO3
Silver nitrate
Silver nitrate is an inorganic compound with chemical formula . This compound is a versatile precursor to many other silver compounds, such as those used in photography. It is far less sensitive to light than the halides...

(aq) → AgI(s) + KNO3
Potassium nitrate
Potassium nitrate is a chemical compound with the formula KNO3. It is an ionic salt of potassium ions K+ and nitrate ions NO3−.It occurs as a mineral niter and is a natural solid source of nitrogen. Its common names include saltpetre , from medieval Latin sal petræ: "stone salt" or possibly "Salt...

(aq)

Organic chemistry

KI serves as a source of iodide in organic synthesis
Organic synthesis
Organic synthesis is a special branch of chemical synthesis and is concerned with the construction of organic compounds via organic reactions. Organic molecules can often contain a higher level of complexity compared to purely inorganic compounds, so the synthesis of organic compounds has...

. A useful application is in the preparation of aryl iodides from arenediazonium salts. For example:



KI, acting as a source of iodide, may also act as a nucleophilic catalyst for the alkylation of alkyl chlorides, bromides, or mesylates.

Industry

KI is a precursor to silver iodide
Silver iodide
Silver iodide is a yellow, inorganic, photosensitive iodide of silver used in photography, in medicine as an antiseptic, and in rainmaking for cloud seeding.-Crystal structure:...

 (AgI) an important chemical in photography. KI is a component in some disinfectants and hair treatment chemicals. KI is also used as a fluorescence quenching agent in biomedical research, an application that takes advantage of collisional quenching of fluorescent substances by the iodide ion. However, for several fluorophores addition of KI in µM-mM concentrations results in increase of fluorescence intensity, and Iodide acts as fluorescence enhancer. Potassium iodide is a component in the electrolyte of dye sensitized solar cells (DSSC) along with iodine.

Nutrition

The major uses of KI include use as a nutritional supplement in animal feeds and also the human diet. For the latter, it is the most common additive used to "iodize" table salt
Sodium chloride
Sodium chloride, also known as salt, common salt, table salt or halite, is an inorganic compound with the formula NaCl. Sodium chloride is the salt most responsible for the salinity of the ocean and of the extracellular fluid of many multicellular organisms...

 (a public health measure to prevent iodine deficiency
Iodine deficiency
Iodine is an essential trace element; the thyroid hormones thyroxine and triiodotyronine contain iodine. In areas where there is little iodine in the diet—typically remote inlandareas where no marine foods are eaten—iodine deficiency gives rise to...

 in populations which get little seafood). The oxidation of iodide causes slow loss of iodine content from iodised salt
Iodised salt
Iodised salt is table salt mixed with a minute amount of various iodine-containing salts. The ingestion of iodide prevents iodine deficiency. Worldwide, iodine deficiency affects about two billion people and is the leading preventable cause of mental retardation. It also causes thyroid gland...

s that are exposed to excess air. The alkali metal iodide salt, over time and exposure to excess oxygen and carbon dioxide, slowly oxidizes to metal carbonate and elemental iodine, which then evaporates. Potassium iodate
Potassium iodate
Potassium iodate is a chemical compound. It is ionic, made up of K+ ions and IO3- ions in a 1:1 ratio.-Chemical properties:Potassium iodate is an oxidizing agent and as such it can cause fires if in contact with combustible materials or reducing agents...

 is used to add iodine to some salts so that the iodine is not lost by oxidation.

For reasons noted above, therapeutic drops of SSKI, or 130 mg tablets of KI as used for nuclear fission accidents, are not used as nutritional supplements, since an SSKI drop or nuclear-emergency tablet provides 300 to 700 times more iodine than the daily adult nutritional requirement. Dedicated nutritional iodide tablets containing 0.15 mg (150 microgram or mcg) of iodide, from KI or from various other sources (such as kelp extract) are marketed as supplements, but they are not to be confused with the much higher pharmaceutical dose preparations.

Pharmaceutical applications

Potassium iodide can be conveniently prepared as a saturated solution, abbreviated SSKI. This method of delivering potassium iodide does not require a method to weigh out the potassium iodide so it can be used in an emergency situation. KI crystals are simply added to water until no more KI will dissolve and instead sits at the bottom of the container. With pure water, the concentration of KI in the solution depends only on the temperature. Potassium iodide is highly soluble in water so SSKI is a concentrated source of KI. At 20 degrees Celsius the solubility of KI is 140-148 grams per 100 grams of water. Because the volumes of KI and water are approximately additive, the resulting SSKI solution will contain about 1.40 gram (1400 mg) KI per milliliter (mL) of solution. This is 100% weight/volume (note units of mass concentration) of KI (one gram KI per mL solution), which is possible because SSKI is significantly more dense than pure water—about 1.72 g/mL. Because KI is about 76.4% iodide by weight, SSKI contains about 764 mg iodide per mL. This concentration) of iodide allows the calculation of the iodide dose per drop, if one knows the number of drops per milliliter. For SSKI, a solution more viscous than water, there are assumed to be 15 drops per mL; the iodide dose is therefore approximately 51 mg per drop, assuming 15 drops/mL. It is conventionally rounded to 50 mg per drop.

The term SSKI is also used, especially by pharmacists, to refer to a U.S.P. pre-prepared solution formula, made by adding exactly KI to water to prepare a solution containing of 1000 mg KI per mL solution (100% wt/volume KI solution), to closely approximate the concentration of SSKI made by saturation. This is essentially interchangeable with SSKI made by saturation, and also contains about 50 mg iodide per drop.
  • Saturated solutions of potassium iodide can be an emergency treatment for hyperthyroidism
    Hyperthyroidism
    Hyperthyroidism is the term for overactive tissue within the thyroid gland causing an overproduction of thyroid hormones . Hyperthyroidism is thus a cause of thyrotoxicosis, the clinical condition of increased thyroid hormones in the blood. Hyperthyroidism and thyrotoxicosis are not synonymous...

     (so-called thyroid storm), as high amounts of iodide temporarily suppress secretion of thyroxine from the thyroid gland. The dose typically begins with a loading dose, then 1/3 mL SSKI (5 drops or 250 mg iodine as iodide), three times per day.

  • Iodide solutions made from a few drops of SSKI added to drinks have also been used as expectorants to increase the water content of respiratory secretions and encourage effective coughing.

  • SSKI has been proposed as a topical
    Topical
    In medicine, a topical medication is applied to body surfaces such as the skin or mucous membranes such as the vagina, anus, throat, eyes and ears.Many topical medications are epicutaneous, meaning that they are applied directly to the skin...

     treatment for sporotrichosis
    Sporotrichosis
    Sporotrichosis is a disease caused by the infection of the fungus Sporothrix schenckii. This fungal disease usually affects the skin, although other rare forms can affect the lungs, joints, bones, and even the brain...

    , but no trials have been conducted to determine the efficacy or side effects of such treatment.

  • Potassium iodide has been used for symptomatic treatment of erythema nodosum
    Erythema nodosum
    Erythema nodosum is an inflammation of the fat cells under the skin characterized by tender red nodules or lumps that are usually seen on both shins...

     patients for persistent lesions whose cause remains unknown. It has been used in cases of erythema nodosum associated with Crohn's disease
    Crohn's disease
    Crohn's disease, also known as regional enteritis, is a type of inflammatory bowel disease that may affect any part of the gastrointestinal tract from mouth to anus, causing a wide variety of symptoms...

    .

Thyroid protection during medical treatment

Thyroid iodine uptake blockade with potassium iodide is used in nuclear medicine
Nuclear medicine
In nuclear medicine procedures, elemental radionuclides are combined with other elements to form chemical compounds, or else combined with existing pharmaceutical compounds, to form radiopharmaceuticals. These radiopharmaceuticals, once administered to the patient, can localize to specific organs...

 scintigraphy
Scintigraphy
Scintigraphy is a form of diagnostic test used in nuclear medicine, wherein radioisotopes are taken internally, and the emitted radiation is captured by external detectors to form two-dimensional images...

 and therapy with some radioiodinated compounds that are not targeted to the thyroid, such as iobenguane
Iobenguane
Iobenguane, also known as metaiodobenzylguanidine or mIBG, or MIBG is a radiopharmaceutical, used in a scintigraphy method called MIBG scan...

 (MIBG), which is used to image or treat neural tissue tumors, or iodinated fibrinogen
Fibrinogen
Fibrinogen is a soluble plasma glycoprotein, synthesised by the liver, that is converted by thrombin into fibrin during blood coagulation. This is achieved through processes in the coagulation cascade that activate the zymogen prothrombin to the serine protease thrombin, which is responsible for...

, which is used in fibrinogen scans to investigate clotting. These compounds contain iodine, but not in the iodide form. However, since they may be ultimately metabolized or break down to radioactive iodide, it is common to administer non-radioactive potassium iodide to ensure that iodide from these radiopharmaceuticals is not sequestered by the normal affinity of the thryoid for iodide.

U.S. Food and Drug Administration
Food and Drug Administration
The Food and Drug Administration is an agency of the United States Department of Health and Human Services, one of the United States federal executive departments...

-approved dosing of potassium iodide for this purpose with iobenguane, is as follows (per 24 hours): infants less than 1 month old, 16 mg; children 1 month to 3 years, 32 mg; children 3 years to 18 years, 65 mg; adults 130 mg. However, some sources recommend alternative dosing regimens.

Not all sources are in agreement on the necessary duration of thyroid blockade, although agreement appears to have been reached about the necessity of blockade for both scintigraphic and therapeutic applications of iobenguane. Commercially available iobenguane is labeled with iodine-123
Iodine-123
Iodine-123 is a radioactive isotope of iodine used in nuclear medicine imaging, including single photon emission computed tomography . The isotope's half-life is 13.22 hours; the decay by electron capture to tellurium-123 emits gamma radiation with predominant energies of 159 keV and 127 keV...

, and product labeling recommends administration of potassium iodide 1 hour prior to administration of the radiopharmaceutical for all age groups, while the European Associated of Nuclear Medicine recommends (for iobenguane labeled with either isotope,) that potassium iodide administration begin one day prior to radiopharmaceutical administration, and continue until the day following the injection, with the exception of new-borns, who do not require potassium iodide doses following radiopharmaceutical injection.

Product labeling for diagnostic iodine-131 iobenguane recommends potassium iodide administration one day before injection and continuing 5 to 7 days following administration, in keeping with the much longer half-life of this isotope and its greater danger to the thyroid. Iodine-131 iobenguane used for therapeutic purposes requires a different pre-medication duration, beginning 24–48 hours prior to iobenguane injection and continuing 10–15 days following injection.

Thyroid protection due to nuclear accidents and emergencies

In 1982, the U.S. Food and Drug Administration
Food and Drug Administration
The Food and Drug Administration is an agency of the United States Department of Health and Human Services, one of the United States federal executive departments...

 approved potassium iodide to protect thyroid
Thyroid
The thyroid gland or simply, the thyroid , in vertebrate anatomy, is one of the largest endocrine glands. The thyroid gland is found in the neck, below the thyroid cartilage...

 glands from radioactive iodine involving accidents or fission emergencies. In an accidental event or attack on a nuclear power plant
Nuclear power plant
A nuclear power plant is a thermal power station in which the heat source is one or more nuclear reactors. As in a conventional thermal power station the heat is used to generate steam which drives a steam turbine connected to a generator which produces electricity.Nuclear power plants are usually...

, or in nuclear bomb fallout
Nuclear fallout
Fallout is the residual radioactive material propelled into the upper atmosphere following a nuclear blast, so called because it "falls out" of the sky after the explosion and shock wave have passed. It commonly refers to the radioactive dust and ash created when a nuclear weapon explodes...

, volatile fission product radionuclides may be released. Of these products, 131I
Iodine-131
Iodine-131 , also called radioiodine , is an important radioisotope of iodine. It has a radioactive decay half-life of about eight days. Its uses are mostly medical and pharmaceutical...

 is one of the most common and is particularly dangerous to the thyroid gland because it may lead to thyroid cancer
Thyroid cancer
Thyroid neoplasm is a neoplasm or tumor of the thyroid. It can be a benign tumor such as thyroid adenoma, or it can be a malignant neoplasm , such as papillary, follicular, medullary or anaplastic thyroid cancer. Most patients are 25 to 65 years of age when first diagnosed; women are more affected...

. By saturating the body with a source of stable iodide prior to exposure, inhaled or ingested 131I tends to be excreted, which prevents radioiodine uptake by the thyroid. The protective effect of KI lasts approximately 24 hours. For optimal prophylaxis, KI must be dosed daily until a risk of significant exposure to radioiodine by either inhalation or ingestion no longer exists.

Emergency 130 milligrams potassium iodide doses provide 100 mg iodide (the other 30 mg is the potassium in the compound), which is roughly 700 times larger than the normal nutritional need (see recommended dietary allowance) for iodine, which is 150 micrograms (0.15 mg) of iodine (as iodide) per day for an adult.

Potassium iodide cannot protect against any other causes of radiation poisoning
Radiation poisoning
Acute radiation syndrome also known as radiation poisoning, radiation sickness or radiation toxicity, is a constellation of health effects which occur within several months of exposure to high amounts of ionizing radiation...

, nor can it provide any degree of protection against dirty bomb
Dirty bomb
A dirty bomb is a speculative radiological weapon that combines radioactive material with conventional explosives. The purpose of the weapon is to contaminate the area around the explosion with radioactive material, hence the attribute "dirty"....

s that produce radionuclides other than radioisotopes of iodine. See fission products and the external links for more details concerning radionuclides.
WHO Recommended Dosage for Radiological Emergencies involving radioactive iodine
Age KI in mg per day
Over 12 years old 130
3 – 12 years old 65
1 – 36 months old 32
< 1 month old 16


The potassium iodide in iodized salt is insufficient for this use. A likely lethal dose
Lethal dose
A lethal dose is an indication of the lethality of a given substance or type of radiation. Because resistance varies from one individual to another, the 'lethal dose' represents a dose at which a given percentage of subjects will die...

 of salt (more than a kilogram) would be needed to equal the potassium iodide in one tablet.

The World Health Organization
World Health Organization
The World Health Organization is a specialized agency of the United Nations that acts as a coordinating authority on international public health. Established on 7 April 1948, with headquarters in Geneva, Switzerland, the agency inherited the mandate and resources of its predecessor, the Health...

 does not recommend KI prophylaxis for adults over 40 years, unless inhaled radiation dose levels are expected to threaten thyroid function; because, the KI side effects increases with age and may exceed the KI protective effects "...unless doses to the thyroid from inhalation rise to levels threatening thyroid function, that is of the order of about 5 Gy
Gray (unit)
The gray is the SI unit of absorbed radiation dose of ionizing radiation , and is defined as the absorption of one joule of ionizing radiation by one kilogram of matter ....

. Such radiation doses will not occur far away from an accident site."

The U.S. Department of Health and Human Services restated these two years later as "The downward KI (potassium iodide) dose adjustment by age group, based on body size considerations, adheres to the principle of minimum effective dose. The recommended standard (daily) dose of KI for all school-age children is the same (65 mg). However, adolescents approaching adult size (i.e., >70 kg [154 lbs]) should receive the full adult dose (130 mg) for maximal block of thyroid radioiodine uptake. Neonates ideally should receive the lowest dose (16 mg) of KI."

SSKI (i.e., the solution of KI rather than tablets) may be used in radioiodine-contamination emergencies (i.e., nuclear accidents) to "block" the thyroid's uptake of radioiodine, at a dose of two drops of SSKI per day for an adult. This is not the same as blocking the thyroid's release of thyroid hormone, for which the adult dose is different (and is actually higher by a factor of 7 or 8), and for which KI anti-radiation pills (not a common medical treatment form of KI) are not usually available in pharmacies, or normally used in hospitals, or by physicians. Although the two forms of potassium iodide are completely interchangeable, normally in practice the SSKI solution, which is the historical medical form of high dose iodine, is generally used for all medical purposes save for radioiodine prophylaxis. For protection of the thyroid against radioiodine (iodine-131) contamination, the convenient standard 130 mg KI pill is used if available. As noted, the equivalent two drops of SSKI may be used for this purpose, if the pills are not available.

Historical use and analysis

Following the Chernobyl nuclear reactor disaster
Chernobyl disaster
The Chernobyl disaster was a nuclear accident that occurred on 26 April 1986 at the Chernobyl Nuclear Power Plant in Ukraine , which was under the direct jurisdiction of the central authorities in Moscow...

 in April, 1986, a saturated solution of potassium iodide (SSKI) was administered to 10.5 million children and 7 million adults in Poland
Poland
Poland , officially the Republic of Poland , is a country in Central Europe bordered by Germany to the west; the Czech Republic and Slovakia to the south; Ukraine, Belarus and Lithuania to the east; and the Baltic Sea and Kaliningrad Oblast, a Russian exclave, to the north...

 as a prophylactic measure against accumulation of radioactive iodine-131
Iodine-131
Iodine-131 , also called radioiodine , is an important radioisotope of iodine. It has a radioactive decay half-life of about eight days. Its uses are mostly medical and pharmaceutical...

 in the thyroid
Thyroid
The thyroid gland or simply, the thyroid , in vertebrate anatomy, is one of the largest endocrine glands. The thyroid gland is found in the neck, below the thyroid cartilage...

 gland. People in the areas immediately surrounding Chernobyl itself, however, were not given the supplement.

Potassium iodide’s (KI) value as a radiation protective (thyroid blocking) agent was demonstrated at the time of the Chernobyl nuclear accident when Soviet authorities distributed it in a 30 km zone around the plant. The purpose was to protect residents from radioactive iodine, a highly carcinogenic material found in nuclear reactors which had been released by the damaged reactor. Only a limited amount of KI was available, but those who received it were protected. Later, the US Nuclear Regulatory Commission (NRC) reported, “thousands of measurements of I-131 (radioactive iodine) activity...suggest that the observed levels were lower than would have been expected had this prophylactic measure not been taken. The use of KI...was credited with permissible iodine content in 97% of the evacuees tested.”

Poland, 300 miles from Chernobyl, also distributed KI to protect its population. Approximately 18 million doses were distributed, with follow-up studies showing no known thyroid cancer among KI recipients. With the passage of time, people living in irradiated areas where KI was not available have developed thyroid cancer at epidemic levels, which is why the US Food and Drug Administration (FDA) reported “The data clearly demonstrate the risks of thyroid radiation...KI can be used [to] provide safe and effective protection against thyroid cancer caused by irradiation.

Chernobyl also demonstrated that the need to protect the thyroid from radiation was greater than expected. Within ten years of the accident, it became clear that thyroid damage caused by released radioactive iodine was virtually the only adverse health effect that could be measured. As reported by the NRC, studies after the accident showed that “As of 1996, except for thyroid cancer, there has been no confirmed increase in the rates of other cancers, including leukemia, among the...public, that have been attributed to releases from the accident.”

But equally important to the question of KI is the fact that radiation releases are not “local” events. Researchers at the World Health Organization accurately located and counted the cancer victims from Chernobyl and were startled to find that “the increase in incidence [of thyroid cancer] has been documented up to 500 km from the accident site...significant doses from radioactive iodine can occur hundreds of kilometers from the site, beyond emergency planning zones." Consequently, far more people than anticipated were affected by the radiation, which caused the United Nations to report in 2002 that “The number of people with thyroid cancer... has exceeded expectations. Over 11,000 cases have already been reported.”

These findings were consistent with studies of the effects of previous radiation releases. In 1945, millions of Japanese were exposed to radiation from nuclear weapons, and the effects can still be measured. Today, nearly half (44.8%) the survivors of Nagasaki studied have identifiable thyroid disease, with the American Medical Association reporting “it is remarkable that a biological effect from a single brief environmental exposure nearly 60 years in the past is still present and can be detected.” This, as well as the development of thyroid cancer among residents in the North Pacific from radioactive fallout following the United States' nuclear weapons testing
Pacific Proving Grounds
The Pacific Proving Grounds was the name used to describe a number of sites in the Marshall Islands and a few other sites in the Pacific Ocean, used by the United States to conduct nuclear testing at various times between 1946 and 1962...

 in the 1950s (on islands nearly 200 miles downwind of the tests) were instrumental in the decision by the FDA in 1978 to issue a request for the availability of KI for thyroid protection in the event of a release from a commercial nuclear power plant or weapons-related nuclear incident. Noting that KI’s effectiveness was “virtually complete” and finding that iodine in the form of potassium iodide (KI) was substantially superior to other forms including iodate (KIO3)
Potassium iodate
Potassium iodate is a chemical compound. It is ionic, made up of K+ ions and IO3- ions in a 1:1 ratio.-Chemical properties:Potassium iodate is an oxidizing agent and as such it can cause fires if in contact with combustible materials or reducing agents...

 in terms of safety, effectiveness, lack of side effects, and speed of onset, the FDA invited manufacturers to submit applications to produce and market KI.

Today, three companies (Anbex, Inc., Fleming Co, and Recip of Sweden) have met the strict FDA requirements for manufacturing and testing of KI, and they offer products (IOSAT, ThyroShield, and Thyro-Safe
Thyrosafe
Thyrosafe is a potassium Iodide tablet manufactured by Recipharm AB. The manufacturer describes it as "the only FDA approved 65 mg. Potassium Iodide tablet." It is marketed in boxes of 20 x 65 mg tablets to be stockpiled in the event of an emergency, such as "a nuclear terrorist attack or...

, respectively) which are available for purchase. The Swedish manufacturing facility for Thyrosafe
Thyrosafe
Thyrosafe is a potassium Iodide tablet manufactured by Recipharm AB. The manufacturer describes it as "the only FDA approved 65 mg. Potassium Iodide tablet." It is marketed in boxes of 20 x 65 mg tablets to be stockpiled in the event of an emergency, such as "a nuclear terrorist attack or...

, a potassium iodide tablet for thyroid protection from radiation manufactured by Recipharm
Recipharm
Recipharm AB is a Swedish company, active as a pharmaceutical contract development and manufacturing organization, with production facilities in Sweden, France, the UK and Switzerland and a development site in Sweden. Recipharm employs over 1400 people and operates nine production facilities...

 AB, was mentioned on the secret US 2008 Critical Foreign Dependencies Initiative
Critical Foreign Dependencies Initiative
The Critical Foreign Dependencies Initiative is a strategy and list, maintained by the United States Department of Homeland Security, of foreign infrastructure which "if attacked or destroyed would critically impact the U.S." A copy of the 2008 list was redacted and leaked by WikiLeaks on 5...

 leaked by Wikileaks in 2010.

It was reported on March 16, 2011, that potassium iodide tablets were given prophylactically to U.S. Naval air crew members flying within 70 nautical miles of the Fukushima Daiichi Nuclear plant damaged in the massive Japanese earthquake (8.9/9.0 magnitude) and ensuing tsunami on March 11, 2011. The measures were seen as precautions, and the Pentagon said no U.S. forces have shown signs of radiation poisoning. By March 20, the US Navy instructed personnel coming within 100 miles of the reactor to take the pills.

Adverse reactions

There have been some reports of potassium iodide treatment causing swelling of the parotid gland
Parotid gland
The paired parotid glands are the largest of the salivary glands. They are each found wrapped around the mandibular ramus, and secrete saliva through Stensen's ducts into the oral cavity, to facilitate mastication and swallowing and to begin the digestion of starches.-Location:The parotid glands...

 (one of the three glands which secrete saliva
Saliva
Saliva , referred to in various contexts as spit, spittle, drivel, drool, or slobber, is the watery substance produced in the mouths of humans and most other animals. Saliva is a component of oral fluid. In mammals, saliva is produced in and secreted from the three pairs of major salivary glands,...

), due to its stimulatory effects on saliva production.

A saturated solution of KI (SSKI) is typically given orally in adult doses of about 250 mg iodide several times a day (5 drops of SSKI assumed to be ⅓ ml) for thyroid blockade (to prevent the thyroid from excreting thyroid hormone) and occasionally this dose is also used when iodide is used as an expectorant. The anti-radioiodine doses used for I-131 uptake blockade are lower, and range downward from 100 mg a day for an adult, to less than this for children (see table). All of these doses should be compared with the far lower dose of iodine needed in normal nutrition, which is only 150 μg per day (150 micrograms, not milligrams).

At maximal doses, and sometimes at much lower doses, side effects of iodide used for medical reasons, in doses of 1000 times the normal nutrional need, may include: acne, loss of appetite, or upset stomach (especially during the first several days, as the body adjusts to the medication). More severe side effects which require notification of a physician are: fever, weakness, unusual tiredness, swelling in the neck or throat, mouth sores, skin rash, nausea, vomiting, stomach pains, irregular heartbeat, numbness or tingling of the hands or feet, or a metallic taste in the mouth.

Precautions

Potassium iodide is a mild irritant and should be handled with gloves. Chronic overexposure can have adverse effects on the thyroid. Potassium iodide is a possible teratogen
Teratology
Teratology is the study of abnormalities of physiological development. It is often thought of as the study of human birth defects, but it is much broader than that, taking in other non-birth developmental stages, including puberty; and other non-human life forms, including plants.- Etymology :The...

.

External links

The source of this article is wikipedia, the free encyclopedia.  The text of this article is licensed under the GFDL.
 
x
OK