Potassium Iodine
   HOME

TheInfoList



OR:

Potassium iodide is a
chemical compound A chemical compound is a chemical substance composed of many identical molecules (or molecular entities) containing atoms from more than one chemical element held together by chemical bonds. A molecule consisting of atoms of only one element ...
,
medication Medication (also called medicament, medicine, pharmaceutical drug, medicinal product, medicinal drug or simply drug) is a drug used to medical diagnosis, diagnose, cure, treat, or preventive medicine, prevent disease. Drug therapy (pharmaco ...
, and
dietary supplement A dietary supplement is a manufactured product intended to supplement a person's diet by taking a pill (pharmacy), pill, capsule (pharmacy), capsule, tablet (pharmacy), tablet, powder, or liquid. A supplement can provide nutrients eithe ...
. It is a medication used for treating
hyperthyroidism Hyperthyroidism is a endocrine disease in which the thyroid gland produces excessive amounts of thyroid hormones. Thyrotoxicosis is a condition that occurs due to elevated levels of thyroid hormones of any cause and therefore includes hyperth ...
, in radiation emergencies, and for protecting the
thyroid gland The thyroid, or thyroid gland, is an endocrine gland in vertebrates. In humans, it is a butterfly-shaped gland located in the neck below the Adam's apple. It consists of two connected lobes. The lower two thirds of the lobes are connected by ...
when certain types of
radiopharmaceutical Radiopharmaceuticals, or medicinal radiocompounds, are a group of pharmaceutical drugs containing radioactive isotopes. Radiopharmaceuticals can be used as diagnostic and therapeutic agents. Radiopharmaceuticals emit radiation themselves, which ...
s are used. It is also used for treating skin sporotrichosis and phycomycosis. It is a supplement used by people with low dietary intake of
iodine Iodine is a chemical element; it has symbol I and atomic number 53. The heaviest of the stable halogens, it exists at standard conditions as a semi-lustrous, non-metallic solid that melts to form a deep violet liquid at , and boils to a vi ...
. It is administered orally. Common side effects include vomiting, diarrhea, abdominal pain, rash, and swelling of the
salivary gland The salivary glands in many vertebrates including mammals are exocrine glands that produce saliva through a system of ducts. Humans have three paired major salivary glands ( parotid, submandibular, and sublingual), as well as hundreds of min ...
s. Other side effects include
allergic reactions Allergies, also known as allergic diseases, are various conditions caused by hypersensitivity of the immune system to typically harmless substances in the environment. These diseases include hay fever, food allergies, atopic dermatitis, alle ...
,
headache A headache, also known as cephalalgia, is the symptom of pain in the face, head, or neck. It can occur as a migraine, tension-type headache, or cluster headache. There is an increased risk of Depression (mood), depression in those with severe ...
,
goitre A goitre (British English), or goiter (American English), is a swelling in the neck resulting from an enlarged thyroid gland. A goitre can be associated with a thyroid that is not functioning properly. Worldwide, over 90% of goitre cases are ...
, and depression. While use during
pregnancy Pregnancy is the time during which one or more offspring gestation, gestates inside a woman's uterus. A multiple birth, multiple pregnancy involves more than one offspring, such as with twins. Conception (biology), Conception usually occurs ...
may harm the baby, its use is still recommended in radiation emergencies. Potassium iodide has the
chemical formula A chemical formula is a way of presenting information about the chemical proportions of atoms that constitute a particular chemical compound or molecule, using chemical element symbols, numbers, and sometimes also other symbols, such as pare ...
K I. Commercially it is made by mixing
potassium hydroxide Potassium hydroxide is an inorganic compound with the formula K OH, and is commonly called caustic potash. Along with sodium hydroxide (NaOH), KOH is a prototypical strong base. It has many industrial and niche applications, most of which utili ...
with iodine. Potassium iodide has been used medically since at least 1820. It is on the
World Health Organization's List of Essential Medicines The WHO Model List of Essential Medicines (aka Essential Medicines List or EML), published by the World Health Organization (WHO), contains the medications considered to be most effective and safe to meet the most important needs in a health s ...
. Potassium iodide is available as a
generic medication A generic drug is a pharmaceutical drug that contains the same chemical substance as a drug that was originally protected by chemical patents. Generic drugs are allowed for sale after the patents on the original drugs expire. Because the active ch ...
and
over the counter Over-the-counter (OTC) drugs are medicines sold directly to a consumer without a requirement for a prescription from a healthcare professional, as opposed to prescription drugs, which may be supplied only to consumers possessing a valid pres ...
. Potassium iodide is also used for the
iodization of salt Iodised salt (American and British English spelling differences#-ise, -ize (-isation, -ization), also spelled iodized salt) is Salt#Edible salt, table salt mixed with a minute amount of various iodine salts. The ingestion of iodine prevents iod ...
.


Medical uses


Dietary supplement

Potassium iodide is a nutritional supplement in animal feeds and also in the human diet. In humans it is the most common additive used for iodizing
table salt In common usage, salt is a mineral composed primarily of sodium chloride (NaCl). When used in food, especially in granulated form, it is more formally called table salt. In the form of a natural crystalline mineral, salt is also known as ro ...
(a public health measure to prevent
iodine deficiency Iodine deficiency is a lack of the trace element iodine, an essential nutrient in the diet. It may result in metabolic problems such as goiter, sometimes as an endemic goiter as well as congenital iodine deficiency syndrome due to untreated ...
in populations that get little seafood). The oxidation of iodide causes slow loss of iodine content from
iodised salt Iodised salt (American and British English spelling differences#-ise, -ize (-isation, -ization), also spelled iodized salt) is Salt#Edible salt, table salt mixed with a minute amount of various iodine salts. The ingestion of iodine prevents iod ...
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 iod''ate'' ( K I O3) is used to iodize some salts so that the iodine is not lost by oxidation.
Dextrose Glucose is a sugar with the molecular formula , which is often abbreviated as Glc. It is overall the most abundant monosaccharide, a subcategory of carbohydrates. It is mainly made by plants and most algae during photosynthesis from water an ...
or
sodium thiosulfate Sodium thiosulfate (sodium thiosulphate) is an inorganic compound with the formula . Typically it is available as the white or colorless pentahydrate (x = 5), which is a white solid that dissolves well in water. The compound is a reducing agent an ...
are often added to iodized table salt to stabilize potassium iodide thus reducing loss of the volatile chemical.


Thyroid protection in nuclear accidents

Thyroid iodine uptake blockade with potassium iodide is used in
nuclear medicine Nuclear medicine (nuclear radiology, nucleology), is a medical specialty involving the application of radioactivity, radioactive substances in the diagnosis and treatment of disease. Nuclear imaging is, in a sense, ''radiology done inside out'', ...
scintigraphy Scintigraphy (from Latin ''scintilla'', "spark"), also known as a gamma scan, is a diagnostic test in nuclear medicine, where radioisotopes attached to drugs that travel to a specific organ or tissue (radiopharmaceuticals) are taken internally a ...
and therapy with some radioiodinated compounds that are not targeted to the thyroid, such as iobenguane (
MIBG Iobenguane, or MIBG, is an aralkylguanidine analog of the adrenergic neurotransmitter norepinephrine (noradrenaline), typically used as a radiopharmaceutical. It acts as a blocking agent for adrenergic neurons. When radiolabeled, it can be use ...
), which is used to image or treat neural tissue tumors, or iodinated
fibrinogen Fibrinogen (coagulation factor I) is a glycoprotein protein complex, complex, produced in the liver, that circulates in the blood of all vertebrates. During tissue and vascular injury, it is converted Enzyme, enzymatically by thrombin to fibrin ...
, which is used in fibrinogen scans to investigate clotting. These compounds contain iodine, but not in the iodide form. 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 thyroid for iodide. The World Health Organization (WHO) provides guidelines for potassium iodide use following a nuclear accident. The dosage of potassium iodide is age-dependent: neonates (<1 month) require 16 mg/day; children aged 1 month to 3 years need 32 mg/day; those aged 3-12 years need 65 mg/day; and individuals over 12 years and adults require 130 mg/day. These dosages list mass of potassium iodide rather than elemental iodine. Potassium iodide can be administered as tablets or as Lugol's iodine solution. The same dosage is recommended by the US
Food and Drug Administration The United States Food and Drug Administration (FDA or US FDA) is a List of United States federal agencies, federal agency of the United States Department of Health and Human Services, Department of Health and Human Services. The FDA is respo ...
.Kowalsky RJ, Falen, SW. Radiopharmaceuticals in Nuclear Pharmacy and Nuclear Medicine. 2nd ed. Washington DC: American Pharmacists Association; 2004. A single daily dose is typically sufficient for 24-hour protection. However, in cases of prolonged or repeated exposure, health authorities may recommend multiple daily doses. Priority for prophylaxis is given to the most sensitive groups: pregnant and breastfeeding women, infants, and children under 18 years. The recommended doses of potassium iodide, which contains a stable isotope of iodine, only protect the thyroid gland from radioactive iodine. It does not offer protection against other radioactive substances. 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 Nuclear medicine (nuclear radiology, nucleology), is a medical specialty involving the application of radioactive substances in the diagnosis and treatment of disease. Nuclear imaging is, in a sense, ''radiology done inside out'', because it reco ...
and therapeutic applications of iobenguane. Commercially available iobenguane is labeled with
iodine-123 Iodine-123 (123I) is a radioactive isotope of iodine used in nuclear medicine imaging, including single-photon emission computed tomography (SPECT) or SPECT/CT exams. The isotope's half-life is 13.2232 hours; the decay by electron capture to t ...
, and product labeling recommends administration of potassium iodide 1 hour prior to administration of the radiopharmaceutical for all age groups, while the European Association 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 Iodine-131 (131I, I-131) is an important radioisotope of iodine discovered by Glenn Seaborg and John Livingood in 1938 at the University of California, Berkeley. It has a radioactive decay half-life of about eight days. It is associated with nu ...
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. In 1982, the U.S.
Food and Drug Administration The United States Food and Drug Administration (FDA or US FDA) is a List of United States federal agencies, federal agency of the United States Department of Health and Human Services, Department of Health and Human Services. The FDA is respo ...
approved potassium iodide to protect
thyroid The thyroid, or thyroid gland, is an endocrine gland in vertebrates. In humans, it is a butterfly-shaped gland located in the neck below the Adam's apple. It consists of two connected lobes. The lower two thirds of the lobes are connected by ...
glands from
radioactive iodine There are 40 known isotopes of iodine (53I) from 108I to 147I; all undergo radioactive decay except 127I, which is stable. Iodine is thus a monoisotopic element. Its longest-lived radioactive isotope, 129I, has a half-life of 16.14 million year ...
involving accidents or fission emergencies. In an accidental event or attack on a
nuclear power plant A nuclear power plant (NPP), also known as a nuclear power station (NPS), nuclear generating station (NGS) or atomic power station (APS) is a thermal power station in which the heat source is a nuclear reactor. As is typical of thermal power st ...
, or in nuclear bomb fallout, volatile
fission product Nuclear fission products are the atomic fragments left after a large atomic nucleus undergoes nuclear fission. Typically, a large nucleus like that of uranium fissions by splitting into two smaller nuclei, along with a few neutrons, the releas ...
radionuclides A radionuclide (radioactive nuclide, radioisotope or radioactive isotope) is a nuclide that has excess numbers of either neutrons or protons, giving it excess nuclear energy, and making it unstable. This excess energy can be used in one of three ...
may be released. Of these products, (Iodine-131) is one of the most common and is particularly dangerous to the thyroid gland because it may lead to
thyroid cancer Thyroid cancer is cancer that develops from the tissues of the thyroid gland. It is a disease in which cells grow abnormally and have the potential to spread to other parts of the body. Symptoms can include swelling or a lump in the neck, ...
. By saturating the body with a source of stable iodide prior to exposure, inhaled or ingested tends to be excreted, which prevents radioiodine uptake by the thyroid. According to one 2000 study "KI administered up to 48 h before exposure can almost completely block thyroid uptake and therefore greatly reduce the thyroid absorbed dose. However, KI administration 96 h or more before exposure has no significant protective effect. In contrast, KI administration after exposure to radioiodine induces a smaller and rapidly decreasing blockade effect." According to the FDA, KI should not be taken as a preventative before radiation exposure. Since KI protects for approximately 24 hours, it must be dosed daily until a risk of significant exposure to radioiodine 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 In the U.S. and Canada, the Reference Daily Intake (RDI) is used in nutrition labeling on food and dietary supplement products to indicate the daily intake level of a nutrient that is considered to be sufficient to meet the requirements of 97â ...
) for iodine, which is 150 micrograms (0.15 mg) of iodine (as iodide) per day for an adult. A typical tablet weighs 160 mg, with 130 mg of potassium iodide and 30 mg of
excipients An excipient is a substance formulated alongside the active ingredient of a medication. They may be used to enhance the active ingredient’s therapeutic properties; to facilitate drug absorption; to reduce viscosity; to enhance solubility; to i ...
, such as binding agents. Potassium iodide cannot protect against any other mechanisms of radiation poisoning, nor can it provide any degree of protection against
dirty bomb A dirty bomb or radiological dispersal device is a radiological weapon that combines radioactive material with conventional explosives. The purpose of the weapon is to contaminate the area around the dispersal agent/conventional explosion with ...
s that produce radionuclides other than those of iodine. The potassium iodide in
iodized salt Iodised salt ( also spelled iodized salt) is table salt mixed with a minute amount of various iodine salts. The ingestion of iodine prevents iodine deficiency. Worldwide, iodine deficiency affects about two billion people and is the leading p ...
is insufficient for this use. A likely
lethal dose In toxicology, the lethal dose (LD) is an indication of the lethal toxicity of a given substance or type of radiation. Because resistance varies from one individual to another, the "lethal dose" represents a dose (usually recorded as dose per kilog ...
of salt (more than a kilogramBy , the maximum allowable concentration of iodine in salt in the U.S. is .01%) would be needed to equal the potassium iodide in one tablet. The
World Health Organization The World Health Organization (WHO) is a list of specialized agencies of the United Nations, specialized agency of the United Nations which coordinates responses to international public health issues and emergencies. It is headquartered in Gen ...
does not recommend KI prophylaxis for adults over 40 years, unless the radiation dose from inhaled radioiodine is expected to threaten thyroid function, because the KI side effects increase 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. Such radiation doses will not occur far away from an accident site." The U.S.
Department of Health and Human Services The United States Department of Health and Human Services (HHS) is a cabinet-level executive branch department of the US federal government created to protect the health of the US people and providing essential human services. Its motto is ...
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 54 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."


Side effects

There is reason for caution with prescribing the ingestion of high doses of potassium iodide and iodate, because their unnecessary use can cause conditions such as the Jod-Basedow phenomena, trigger and/or worsen
hyperthyroidism Hyperthyroidism is a endocrine disease in which the thyroid gland produces excessive amounts of thyroid hormones. Thyrotoxicosis is a condition that occurs due to elevated levels of thyroid hormones of any cause and therefore includes hyperth ...
and
hypothyroidism Hypothyroidism is an endocrine disease in which the thyroid gland does not produce enough thyroid hormones. It can cause a number of symptoms, such as cold intolerance, poor ability to tolerate cold, fatigue, extreme fatigue, muscle aches, co ...
, and then cause temporary or even permanent thyroid conditions. It can also cause
sialadenitis Sialadenitis (sialoadenitis) is inflammation of salivary glands, usually the major ones, the most common being the parotid gland, followed by submandibular and sublingual glands. It should not be confused with sialadenosis (sialosis) which is a ...
(an inflammation of the salivary gland), gastrointestinal disturbances, and rashes. Potassium iodide is also not recommended for people with
dermatitis herpetiformis Dermatitis herpetiformis (DH) is a chronic autoimmune blistering skin condition, characterised by intensely itchy blisters filled with a watery fluid. DH is a cutaneous manifestation of coeliac disease, although the exact causal mechanism is not ...
and hypocomplementemic vasculitis â€“ conditions that are linked to a risk of iodine sensitivity. There have been some reports of potassium iodide treatment causing swelling of the
parotid gland The parotid gland is a major salivary gland in many animals. In humans, the two parotid glands are present on either side of the mouth and in front of both ears. They are the largest of the salivary glands. Each parotid is wrapped around the m ...
(one of the three
glands A gland is a Cell (biology), cell or an Organ (biology), organ in an animal's body that produces and secretes different substances that the organism needs, either into the bloodstream or into a body cavity or outer surface. A gland may also funct ...
that secrete
saliva Saliva (commonly referred as spit or drool) is an extracellular fluid produced and secreted by salivary glands in the mouth. In humans, saliva is around 99% water, plus electrolytes, mucus, white blood cells, epithelial cells (from which ...
), due to its stimulatory effects on saliva production.McCance; Huether. "Pathophysiology: The biological basis for disease in Adults and Children". 5th Edition. Elsievier Publishing A saturated solution of KI (SSKI) is typically given orally in adult doses several times a day (5 drops of SSKI assumed to be  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 total dose is about one gram KI per day for an adult). The anti-radioiodine doses used for 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 Î¼g 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 nutritional 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 that 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. In the event of a radioiodine release the ingestion of prophylaxis potassium iodide, if available, or even iodate, would rightly take precedence over perchlorate administration, and would be the first line of defence in protecting the population from a radioiodine release. However, in the event of a radioiodine release too massive and widespread to be controlled by the limited stock of iodide and iodate prophylaxis drugs, then the addition of perchlorate ions to the water supply, or distribution of perchlorate tablets would serve as a cheap, efficacious, second line of defense against
carcinogenic A carcinogen () is any agent that promotes the development of cancer. Carcinogens can include synthetic chemicals, naturally occurring substances, physical agents such as ionizing and non-ionizing radiation, and Biological agent, biologic agent ...
radioiodine bioaccumulation. The ingestion of goitrogen drugs is, much like potassium iodide also not without its dangers, such as
hypothyroidism Hypothyroidism is an endocrine disease in which the thyroid gland does not produce enough thyroid hormones. It can cause a number of symptoms, such as cold intolerance, poor ability to tolerate cold, fatigue, extreme fatigue, muscle aches, co ...
. In all these cases however, despite the risks, the prophylaxis benefits of intervention with iodide, iodate or perchlorate outweigh the serious cancer risk from radioiodine
bioaccumulation Bioaccumulation is the gradual accumulation of substances, such as pesticides or other chemicals, in an organism. Bioaccumulation occurs when an organism absorbs a substance faster than it can be lost or eliminated by catabolism and excretion. T ...
in regions where radioiodine has sufficiently contaminated the environment.


Industrial uses

KI is used with silver nitrate to make
silver iodide Silver iodide is an inorganic compound with the formula Ag I. The compound is a bright yellow solid, but samples almost always contain impurities of metallic silver that give a grey colouration. The silver contamination arises because some samp ...
(AgI), an important chemical in film 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 sensitised solar cells (DSSC) along with iodine. Potassium iodide finds its most important applications in organic synthesis mainly in the preparation of aryl iodides in the Sandmeyer reaction, starting from aryl amines. Aryl iodides are in turn used to attach aryl groups to other organics by nucleophilic substitution, with iodide ion as the leaving group.


Chemistry

Potassium iodide is an
ionic compound In chemistry, a salt or ionic compound is a chemical compound consisting of an assembly of positively charged ions (Cation, cations) and negatively charged ions (Anion, anions), which results in a compound with no net electric charge (electrica ...
which is made of the following
ion An ion () is an atom or molecule with a net electrical charge. The charge of an electron is considered to be negative by convention and this charge is equal and opposite to the charge of a proton, which is considered to be positive by convent ...
s: . It crystallises in the
sodium chloride Sodium chloride , commonly known as Salt#Edible salt, edible salt, is an ionic compound with the chemical formula NaCl, representing a 1:1 ratio of sodium and chloride ions. It is transparent or translucent, brittle, hygroscopic, and occurs a ...
structure. It is produced industrially by treating KOH with iodine. It is a white
salt In common usage, salt is a mineral composed primarily of sodium chloride (NaCl). When used in food, especially in granulated form, it is more formally called table salt. In the form of a natural crystalline mineral, salt is also known as r ...
, which is the most commercially significant iodide compound, with approximately 37,000 tons produced in 1985. It absorbs water less readily than
sodium iodide Sodium iodide (chemical formula NaI) is an ionic compound formed from the chemical reaction of sodium metal and iodine. Under standard conditions, it is a white, water-soluble solid comprising a 1:1 mix of sodium cations (Na+) and iodide anions ...
, making it easier to work with. Aged and impure samples are yellow because of the slow
oxidation Redox ( , , reduction–oxidation or oxidation–reduction) is a type of chemical reaction in which the oxidation states of the reactants change. Oxidation is the loss of electrons or an increase in the oxidation state, while reduction is ...
of the salt to
potassium carbonate Potassium carbonate is the inorganic compound with the formula . It is a white salt, which is soluble in water and forms a strongly alkaline solution. It is deliquescent, often appearing as a damp or wet solid. Potassium carbonate is mainly used ...
and elemental
iodine Iodine is a chemical element; it has symbol I and atomic number 53. The heaviest of the stable halogens, it exists at standard conditions as a semi-lustrous, non-metallic solid that melts to form a deep violet liquid at , and boils to a vi ...
. :


Inorganic chemistry

Since the
iodide An iodide ion is I−. Compounds with iodine in formal oxidation state −1 are called iodides. In everyday life, iodide is most commonly encountered as a component of iodized salt, which many governments mandate. Worldwide, iodine deficiency ...
ion is a mild
reducing agent In chemistry, a reducing agent (also known as a reductant, reducer, or electron donor) is a chemical species that "donates" an electron to an (called the , , , or ). Examples of substances that are common reducing agents include hydrogen, carbon ...
, is easily oxidised to
iodine Iodine is a chemical element; it has symbol I and atomic number 53. The heaviest of the stable halogens, it exists at standard conditions as a semi-lustrous, non-metallic solid that melts to form a deep violet liquid at , and boils to a vi ...
() by powerful oxidising agents such as
chlorine Chlorine is a chemical element; it has Symbol (chemistry), symbol Cl and atomic number 17. The second-lightest of the halogens, it appears between fluorine and bromine in the periodic table and its properties are mostly intermediate between ...
: : 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 (DCM, methylene chloride, or methylene bichloride) is an organochlorine compound with the formula . This colorless, volatile liquid with a chloroform-like, sweet odor is widely used as a solvent. Although it is not miscible with ...
. As formed under acidic conditions, hydriodic acid (HI) is a stronger reducing agent. Like other iodide salts, KI forms
triiodide In chemistry, triiodide usually refers to the triiodide ion, . This anion, one of the polyhalogen ions, is composed of three iodine atoms. It is formed by combining aqueous solutions of iodide salts and iodine. Some salts of the anion have been ...
() when combined with elemental
iodine Iodine is a chemical element; it has symbol I and atomic number 53. The heaviest of the stable halogens, it exists at standard conditions as a semi-lustrous, non-metallic solid that melts to form a deep violet liquid at , and boils to a vi ...
. : Unlike , salts can be highly water-soluble. Through this reaction,
iodine Iodine is a chemical element; it has symbol I and atomic number 53. The heaviest of the stable halogens, it exists at standard conditions as a semi-lustrous, non-metallic solid that melts to form a deep violet liquid at , and boils to a vi ...
is used in
redox Redox ( , , reduction–oxidation or oxidation–reduction) is a type of chemical reaction in which the oxidation states of the reactants change. Oxidation is the loss of electrons or an increase in the oxidation state, while reduction is t ...
titration Titration (also known as titrimetry and volumetric analysis) is a common laboratory method of Quantitative research, quantitative Analytical chemistry, chemical analysis to determine the concentration of an identified analyte (a substance to be ...
s. Aqueous ( Lugol's iodine) solution is used as a disinfectant and as an etchant for gold surfaces. Potassium iodide and
silver nitrate Silver nitrate is an inorganic compound with chemical formula . It 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. It was once called ''lunar causti ...
are used to make silver(I) iodide, which is used for high speed
photographic film Photographic film is a strip or sheet of transparent film base coated on one side with a gelatin photographic emulsion, emulsion containing microscopically small light-sensitive silver halide crystals. The sizes and other characteristics of the ...
and for
cloud seeding Cloud seeding is a type of weather modification that aims to change the amount or type of precipitation, mitigate hail, or disperse fog. The usual objective is to increase rain or snow, either for its own sake or to prevent precipitation from ...
: :


Organic chemistry

KI serves as a source of iodide in
organic synthesis Organic synthesis is a branch of chemical synthesis concerned with the construction of organic compounds. Organic compounds are molecules consisting of combinations of covalently-linked hydrogen, carbon, oxygen, and nitrogen atoms. Within the gen ...
. A useful application is in the preparation of aryl iodides from arenediazonium salts. : KI, acting as a source of iodide, may also act as a nucleophilic catalyst for the alkylation of alkyl
chloride The term chloride refers to a compound or molecule that contains either a chlorine anion (), which is a negatively charged chlorine atom, or a non-charged chlorine atom covalently bonded to the rest of the molecule by a single bond (). The pr ...
s,
bromide A bromide ion is the negatively charged form (Br−) of the element bromine, a member of the halogens group on the periodic table. Most bromides are colorless. Bromides have many practical roles, being found in anticonvulsants, flame-retard ...
s, or
mesylate In organosulfur chemistry, a mesylate is any salt or ester of methanesulfonic acid (). In salts, the mesylate is present as the anion. When modifying the international nonproprietary name of a pharmaceutical substance containing the gr ...
s.


History

Potassium iodide has been used medically since at least 1820. Some of the earliest uses included cures for
syphilis Syphilis () is a sexually transmitted infection caused by the bacterium ''Treponema pallidum'' subspecies ''pallidum''. The signs and symptoms depend on the stage it presents: primary, secondary, latent syphilis, latent or tertiary. The prim ...
,
lead Lead () is a chemical element; it has Chemical symbol, symbol Pb (from Latin ) and atomic number 82. It is a Heavy metal (elements), heavy metal that is density, denser than most common materials. Lead is Mohs scale, soft and Ductility, malleabl ...
and
mercury poisoning Mercury poisoning is a type of metal poisoning due to exposure to mercury. Symptoms depend upon the type, dose, method, and duration of exposure. They may include muscle weakness, poor coordination, numbness in the hands and feet, skin rashe ...
.


Chernobyl

Potassium iodide's (KI) value as a radiation protective (thyroid blocking) agent was demonstrated following the Chernobyl nuclear reactor disaster in April 1986. A saturated solution of potassium iodide (SSKI) was administered to 10.5 million children and 7 million adults in
Poland Poland, officially the Republic of Poland, is a country in Central Europe. It extends from the Baltic Sea in the north to the Sudetes and Carpathian Mountains in the south, bordered by Lithuania and Russia to the northeast, Belarus and Ukrai ...
as a preventative measure against accumulation of radioactive in the
thyroid The thyroid, or thyroid gland, is an endocrine gland in vertebrates. In humans, it is a butterfly-shaped gland located in the neck below the Adam's apple. It consists of two connected lobes. The lower two thirds of the lobes are connected by ...
gland. Reports differ concerning whether people in the areas immediately surrounding Chernobyl itself were given the supplement. However 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." 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 oprovide 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 radioactivity releases are not "local" events. Researchers at the World Health Organization accurately located and counted the residents with cancer from Chernobyl and were startled to find that "the increase in incidence f thyroid cancerhas 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."


Hiroshima and Nagasaki

The Chernobyl findings were consistent with studies of the effects of previous radioactivity releases. In 1945, several hundreds of thousands of people working and residing in the Japanese cities of
Hiroshima is the capital of Hiroshima Prefecture in Japan. , the city had an estimated population of 1,199,391. The gross domestic product (GDP) in Greater Hiroshima, Hiroshima Urban Employment Area, was US$61.3 billion as of 2010. Kazumi Matsui has b ...
and
Nagasaki , officially , is the capital and the largest Cities of Japan, city of Nagasaki Prefecture on the island of Kyushu in Japan. Founded by the Portuguese, the port of Portuguese_Nagasaki, Nagasaki became the sole Nanban trade, port used for tr ...
were exposed to high levels of radiation after atomic bombs were detonated over the two cities by the United States. Survivors of the A-bombings, also known as ''
hibakusha ' ( or ; or ; or ) is a word of Japanese origin generally designating the people affected by the atomic bombings of Hiroshima and Nagasaki by the United States at the end of World War II. Definition The word is Japanese, originally written i ...
'', have markedly high rates of thyroid disease; a 2006 study of 4091 ''hibakusha'' found nearly half the participants (1833; 44.8%) had an identifiable thyroid disease. An editorial in ''The Journal of the American Medical Association'' regarding thyroid diseases in both ''hibakusha'' and those affected by the Chernobyl disaster reports that " straight line adequately describes the relationship between radiation dose and thyroid cancer incidence" and states "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."


Nuclear weapons testing

The development of thyroid cancer among residents in the
North Pacific The Pacific Ocean is the largest and deepest of Earth's five oceanic divisions. It extends from the Arctic Ocean in the north to the Southern Ocean, or, depending on the definition, to Antarctica in the south, and is bounded by the contine ...
from radioactive fallout following the United States' nuclear weapons testing in the 1950s (on islands nearly 200 miles downwind of the tests) were instrumental in the 1978 decision by the
FDA The United States Food and Drug Administration (FDA or US FDA) is a federal agency of the Department of Health and Human Services. The FDA is responsible for protecting and promoting public health through the control and supervision of food ...
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 KI was substantially superior to other forms including iodate (KIO3) 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.


Fukushima

It was reported on 16 March 2011, that potassium iodide tablets were given preventively to U.S. Naval air crew members flying within 70 nautical miles of the
Fukushima Daiichi Nuclear Power Plant The is a disabled nuclear power plant located on a site in the towns of ÅŒkuma, Fukushima, ÅŒkuma and Futaba, Fukushima, Futaba in Fukushima Prefecture, Japan. The plant Fukushima Daiichi nuclear disaster, suffered major damage from the 201 ...
damaged in the earthquake (8.9/9.0 magnitude) and ensuing tsunami on 11 March 2011. The measures were seen as precautions, and the Pentagon said no U.S. forces have shown signs of radiation poisoning. By 20 March, the US Navy instructed personnel coming within 100 miles of the reactor to take the pills.


The Netherlands

In the Netherlands, the central storage of iodine-pills is located in
Zoetermeer Zoetermeer () is a city in the Western Netherlands, in the province of South Holland. The municipality covers an area of of which is water. A small village until the late 1960s, it had 6,392 inhabitants in 1950. By 2023 this had grown to 126.998 ...
, near
The Hague The Hague ( ) is the capital city of the South Holland province of the Netherlands. With a population of over half a million, it is the third-largest city in the Netherlands. Situated on the west coast facing the North Sea, The Hague is the c ...
. In 2017, the Dutch government distributed pills to hundreds of thousands of residents who lived within a certain distance of nuclear power plants and met some other criteria.


Belgium

By 2020, potassium iodide tablets are made available free of charge for all residents in all pharmacies throughout the country.


Formulations

Three companies (Anbex, Inc., Fleming Co, and Recipharm of Sweden) have met the strict FDA requirements for manufacturing and testing of KI, and they offer products (IOSAT, ThyroShield, and ThyroSafe, respectively) which are available for purchase. In 2012, Fleming Co. sold all its product rights and manufacturing facility to other companies and no longer exists. ThyroShield is currently not in production. Tablets of potassium iodide are supplied for emergency purposes related to blockade of radioiodine uptake, a common form of radiation poisoning due to environmental contamination by the short-lived fission product . Potassium iodide may also be administered pharmaceutically for
thyroid storm Thyroid storm is a rare but severe and life-threatening complication of hyperthyroidism. It occurs when an overactive thyroid leads to hypermetabolism, which can cause death from cardiac arrest or multiple organ failure. It is characterized by ...
. 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 micrograms (μg)) 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. Potassium iodide can be conveniently prepared in a saturated solution, abbreviated SSKI. This method of delivering potassium iodide doesn't require a method to weigh out the potassium iodide, thus allowing it to 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 thus 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 1.00 gram (1000 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 1.67 g/mL. Because KI is about 76.4% iodide by weight, SSKI contains about 764 mg iodide per mL. This
concentration In chemistry, concentration is the abundance of a constituent divided by the total volume of a mixture. Several types of mathematical description can be distinguished: '' mass concentration'', '' molar concentration'', '' number 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. 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 KI to water to prepare a solution containing 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 is a endocrine disease in which the thyroid gland produces excessive amounts of thyroid hormones. Thyrotoxicosis is a condition that occurs due to elevated levels of thyroid hormones of any cause and therefore includes hyperth ...
(so-called
thyroid storm Thyroid storm is a rare but severe and life-threatening complication of hyperthyroidism. It occurs when an overactive thyroid leads to hypermetabolism, which can cause death from cardiac arrest or multiple organ failure. It is characterized by ...
), as high amounts of iodide temporarily suppress secretion of
thyroxine Thyroxine, also known as T4, is a hormone produced by the thyroid gland. It is the primary form of thyroid hormone found in the blood and acts as a prohormone of the more active thyroid hormone, triiodothyronine (T3). Thyroxine and its acti ...
from the thyroid gland. The dose typically begins with a loading dose, then  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
expectorant Mucoactive agents are a class of pharmacologic agents that include expectorants, mucolytics, mucoregulators, and mucokinetics that can affect the volume, viscosity, transportation, and composition of mucus or sputum. They often aid in clearing ...
s to increase the water content of respiratory secretions and encourage effective coughing. *SSKI has been proposed as a
topical A topical medication is a medication that is applied to a particular place on or in the body. Most often topical medication means application to body surfaces such as the skin or mucous membranes to treat ailments via a large range of classes ...
treatment for sporotrichosis, 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 (EN) is an inflammatory condition characterized by inflammation of subcutaneous fat tissue, resulting in painful red/blue lumps or nodules that are usually seen symmetrically on both shins, on the thighs, arms, and elsewhere. I ...
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 is a type of inflammatory bowel disease (IBD) that may affect any segment of the gastrointestinal tract. Symptoms often include abdominal pain, diarrhea, fever, abdominal distension, and weight loss. Complications outside of the ...
. *Due to its high potassium content, SSKI is extremely bitter, and if possible it is administered in a sugar cube or small ball of bread. It may also be mixed into much larger volumes of juices. *Neither SSKI or KI tablets form nutritional supplements, since the nutritional requirement for iodine is only 150 micrograms (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.


References


External links

*
World Health Organization's guidelines for iodine prophylaxis following a nuclear accident
{{DEFAULTSORT:Potassium Iodide Potassium compounds Alkali metal iodides Disaster preparedness Expectorants Iodides Food additives Metal halides Photographic chemicals Radiobiology World Health Organization essential medicines Wikipedia medicine articles ready to translate Rock salt crystal structure Ophthalmology drugs