Iodine is a

chemical element A chemical element is a chemical substance whose atoms all have the same number of protons. The number of protons is called the atomic number of that element. For example, oxygen has an atomic number of 8: each oxygen atom has 8 protons in its ...

with many uses in medicine, depending on the form. Elemental iodine and iodophors are topical

antiseptic An antiseptic ( and ) is an antimicrobial substance or compound that is applied to living tissue to reduce the possibility of sepsis, infection, or putrefaction. Antiseptics are generally distinguished from ''antibiotics'' by the latter's abil ...

s. – This article deals with iodine for topical use. The listed brand names (Iodoflex, Iodosorb) are more appropriately attributed to cadexomer iodine, ATC code D03AX01. Iodine, in non-elemental form, functions as an essential nutrient in human biology (see

iodine in biology Iodine is an essential trace element in biological systems. It has the distinction of being the heaviest element commonly needed by living organisms as well as the second-heaviest known to be used by any form of life (only tungsten, a component o ...

). Organic compounds containing iodine are also useful

iodinated contrast Iodinated contrast is a form of water-soluble, intravenous radiocontrast agent containing iodine, which enhances the visibility of vascular structures and organs during radiography, radiographic procedures. Some pathologies, such as cancer, have p ...

agents in X-ray imaging. Common side effects when applied to the skin include irritation and discoloration. Supplementation 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 ...

is recommended in regions where deficiency is common, otherwise it is not recommended. Iodine is an

essential trace element __NOTOC__ A trace element is a chemical element of a minute quantity, a trace amount, especially used in referring to a micronutrient, but is also used to refer to minor elements in the composition of a rock, or other chemical substance. In nutrit ...

. In 1811,

Bernard Courtois Bernard Courtois (), also spelled Barnard Courtois, (8 February 1777 – 27 September 1838) was a French chemist credited with first isolating iodine, making early photography possible. By 1811 the Napoleonic Wars had made the government-contro ...

isolated iodine from

seaweed Seaweed, or macroalgae, refers to thousands of species of macroscopic, multicellular, marine algae. The term includes some types of ''Rhodophyta'' (red), '' Phaeophyta'' (brown) and ''Chlorophyta'' (green) macroalgae. Seaweed species such as ...

while in 1820 Jean-Francois Coindet linked iodine intake to goiter size. It initially came into use as a disinfectant and a treatment for goiter. The following forms of iodine are found 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 Potassium iodide is a chemical compound, medication, and dietary supplement. It is a medication used for treating hyperthyroidism, in radiation emergencies, and for protecting the thyroid gland when certain types of radiopharmaceuticals are u ...

* Amidotrizoate *

Iohexol Iohexol, sold under the trade name Iodaque among others, is a contrast agent used for X-ray imaging. This includes when visualizing arteries, veins, ventricles of the brain, the urinary system, and joints, as well as during computed tomograph ...

* Meglumine iotroxat * Povidone iodine * "Iodine" – less ambiguously known as iodized oil In addition,

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 ...

with non-elemental iodine, known as

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 available in more than 110 countries.

Forms and formulations

Elemental iodine

Elemental iodine is used as an

either as the element, or as the water-soluble

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 ...

anion I₃⁻ generated ''in situ'' by adding

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 ...

to poorly water-soluble elemental iodine (the reverse chemical reaction makes some free elemental iodine available for antisepsis). In the alternative, iodine may be produced from

iodophor An iodophor is a preparation containing iodine complexed with a solubilizing agent, such as a surfactant or water-soluble polymers such as povidone (forming povidone-iodine), The result is a water-soluble material that releases free iodine when ...

s, which contain iodine complexed with a solubilizing agent (the iodide ion may be thought of loosely as the iodophor in triiodide water solutions). Examples of such preparations include: *

Tincture of iodine Tincture of iodine, iodine tincture, or weak iodine solution is an antiseptic. It is usually 2% elemental iodine, along with potassium iodide or sodium iodide, dissolved in a mixture of ethanol and water. Tincture solutions are characterized by ...

: iodine in ethanol, or iodine and

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 ...

in a mixture of ethanol and water. *

Lugol's iodine Lugol's iodine, also known as aqueous iodine and strong iodine solution, is a solution of potassium iodide with iodine in water. It is a medication and disinfectant used for a number of purposes. Taken by mouth it is used to treat thyrotoxic ...

: iodine and iodide in water alone, forming mostly triiodide. Unlike tincture of iodine, Lugol's iodine has a minimised amount of the free iodine (I₂) component. *

Iodine glycerin 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 viol ...

, a preparation used in dentistry. *

Povidone iodine Povidone-iodine (PVP-I), also known as iodopovidone, is an antiseptic used for skin disinfection before and after surgery. It may be used both to disinfect the hands of healthcare providers and the skin of the person they are caring for. It may ...

(an

). * Iodine-V: iodine (I₂) and

fulvic acid Humic substances (HS) are colored relatively recalcitrant organic compounds naturally formed during long-term decomposition and transformation of biomass residues. The color of humic substances varies from bright yellow to light or dark brown lead ...

form a

clathrate compound A clathrate is a chemical substance consisting of a lattice that traps or contains molecules. The word ''clathrate'' is derived from the Latin (), meaning 'with bars, latticed'. Most clathrate compounds are polymeric and completely envelop the ...

(iodine molecules are "caged" by fulvic acid in this host-guest complex). A water-soluble, solid, stable, crystalline complex. Unlike other iodophors, Iodine-V only contains iodine in molecular (I₂) form. The antimicrobial action of iodine is quick and works at low concentrations, and thus it is used in operating theatres. Its specific mode of action is unknown. It penetrates into microorganisms and attacks particular amino acids (such as

cysteine Cysteine (; symbol Cys or C) is a semiessential proteinogenic amino acid with the chemical formula, formula . The thiol side chain in cysteine enables the formation of Disulfide, disulfide bonds, and often participates in enzymatic reactions as ...

and

methionine Methionine (symbol Met or M) () is an essential amino acid in humans. As the precursor of other non-essential amino acids such as cysteine and taurine, versatile compounds such as SAM-e, and the important antioxidant glutathione, methionine play ...

nucleotides Nucleotides are Organic compound, organic molecules composed of a nitrogenous base, a pentose sugar and a phosphate. They serve as monomeric units of the nucleic acid polymers – deoxyribonucleic acid (DNA) and ribonucleic acid (RNA), both o ...

, and

fatty acid In chemistry, in particular in biochemistry, a fatty acid is a carboxylic acid with an aliphatic chain, which is either saturated and unsaturated compounds#Organic chemistry, saturated or unsaturated. Most naturally occurring fatty acids have an ...

s, ultimately resulting in

cell death Cell death is the event of a biological cell ceasing to carry out its functions. This may be the result of the natural process of old cells dying and being replaced by new ones, as in programmed cell death, or may result from factors such as di ...

. It also has an

antiviral Antiviral drugs are a class of medication used for treating viral infections. Most antivirals target specific viruses, while a broad-spectrum antiviral is effective against a wide range of viruses. Antiviral drugs are a class of antimicrobials ...

action, but nonlipid viruses and

parvovirus Parvoviruses are a family of animal viruses that constitute the family ''Parvoviridae''. They have linear, single-stranded DNA (ssDNA) genomes that typically contain two genes encoding for a replication initiator protein, called NS1, and the p ...

es are less sensitive than lipid enveloped viruses. Iodine probably attacks surface proteins of enveloped viruses, and it may also destabilise membrane fatty acids by reacting with unsaturated carbon bonds.

Iodine-containing salts

As a nutrient, iodine enters cells as the

ion; iodide is also the form of iodine found in food such as kelp. The form of iodide salt most commonly used medically is

potassium iodide Potassium iodide is a chemical compound, medication, and dietary supplement. It is a medication used for treating hyperthyroidism, in radiation emergencies, and for protecting the thyroid gland when certain types of radiopharmaceuticals are u ...

. At low doses, it is one of the options for making iodized salt, along with the more stable

potassium iodate Potassium iodate ( K I O3) is an ionic inorganic compound with the formula . It is a white salt that is soluble in water. Preparation and properties It can be prepared by reacting a potassium-containing base such as potassium hydroxide with iod ...

. A saturated solution of

is used to treat acute

thyrotoxicosis 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 ...

. It is also used to block uptake of

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 ...

in the thyroid gland (see isotopes section above), when this isotope is used as part of radiopharmaceuticals (such as

iobenguane 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 ...

) that are not targeted to the thyroid or thyroid-type tissues. Iodine-131 (usually as iodide) is a component of

nuclear fallout Nuclear fallout is residual radioactive material that is created by the reactions producing a nuclear explosion. It is initially present in the mushroom cloud, radioactive cloud created by the explosion, and "falls out" of the cloud as it is ...

, and is particularly dangerous owing to the thyroid gland's propensity to concentrate ingested iodine and retain it for periods longer than this isotope's radiological half-life of eight days. For this reason, people at risk of exposure to environmental radioactive iodine (iodine-131) in fallout may be instructed to take non-radioactive potassium iodide tablets. The typical adult dose is one 130 mg tablet per 24 hours, supplying 100 mg (100,000 micrograms) of ionic iodine (the typical daily dose of iodine for normal health is on the order of 100 micrograms). Ingestion of this large dose of non-radioactive iodine minimises the uptake of radioactive iodine by the thyroid gland. Before the advent of organic

chelating agent Chelation () is a type of bonding of ions and their molecules to metal ions. It involves the formation or presence of two or more separate coordinate bonds between a polydentate (multiple bonded) ligand and a single central metal atom. These l ...

s, salts of iodide were given orally in the treatment of

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 ...

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 ...

, such as heavily popularized by Louis Melsens and many nineteenth and early twentieth century doctors."On the Employment of Iodide of Potassium as a Remedy for the Affections Caused by Lead and Mercury"
in ''Br Foreign Med Chir Rev.'' 1853 Jan; 11(21): 201–224.

Organoiodine compounds

As an element with high

electron density Electron density or electronic density is the measure of the probability of an electron being present at an infinitesimal element of space surrounding any given point. It is a scalar quantity depending upon three spatial variables and is typical ...

and atomic number, iodine absorbs X-rays weaker than 33.3 keV due to the

photoelectric effect The photoelectric effect is the emission of electrons from a material caused by electromagnetic radiation such as ultraviolet light. Electrons emitted in this manner are called photoelectrons. The phenomenon is studied in condensed matter physi ...

of the innermost electrons. Organoiodine compounds are used with intravenous injection as X-ray

radiocontrast Radiocontrast agents are substances used to enhance the visibility of internal structures in X-ray-based imaging techniques such as computed tomography (contrast CT), projectional radiography, and fluoroscopy. Radiocontrast agents are typically iod ...

agents. This application is often in conjunction with advanced X-ray techniques such as

angiography Angiography or arteriography is a medical imaging technique used to visualize the inside, or lumen, of blood vessels and organs of the body, with particular interest in the arteries, veins, and the heart chambers. Modern angiography is perfo ...

and

CT scan A computed tomography scan (CT scan), formerly called computed axial tomography scan (CAT scan), is a medical imaging technique used to obtain detailed internal images of the body. The personnel that perform CT scans are called radiographers or ...

ning. At present, all water-soluble radiocontrast agents rely on iodine-containing compounds. *

(contrast agent) * Amidotrizoate (contrast agent) * Meglumine iotroxate (contrast agent) *

Iopanoic acid Iopanoic acid is an iodine-containing radiocontrast medium used in cholecystography. Both iopanoic acid and ipodate sodium are potent inhibitors of thyroid hormone release from thyroid gland, as well as of peripheral conversion of thyroxine (T4) ...

(contrast agent) '' Iodized oil'', made by reacting ether

ester In chemistry, an ester is a compound derived from an acid (either organic or inorganic) in which the hydrogen atom (H) of at least one acidic hydroxyl group () of that acid is replaced by an organyl group (R). These compounds contain a distin ...

s of

s form vegetable oil with

hydroiodic acid Hydroiodic acid (or hydriodic acid) is a colorless liquid. It is an aqueous solution of hydrogen iodide with the chemical formula . It is a strong acid, in which hydrogen iodide is ionized completely in an aqueous solution. Concentrated aqueous ...

, is another important organoiodine preparation. As an iodine supplement, it is given by mouth once per year to prevent endemic goitre in remote communities. It is also used as a non-water-soluble radiocontrast. Other organoiodine drugs include: *

Amiodarone Amiodarone is an antiarrhythmic medication used to treat and prevent a number of types of cardiac dysrhythmias. This includes ventricular tachycardia, ventricular fibrillation, and wide complex tachycardia, atrial fibrillation, and paroxys ...

, an antiarrhythmic drug. *

Iodinated glycerol 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 viol ...

, historically used as a mucolytic.

References

{{Portal bar , Medicine World Health Organization essential medicines Wikipedia medicine articles ready to translate Iodine

Forms and formulations

Elemental iodine

Iodine-containing salts

Organoiodine compounds

See also

References