Iodine (medical use)

Topical antiseptic and supplement

For "Iodine" (capsule, iodized oil) as found in the WHO Model List of Essential Medicines[1], see Lipiodol.

Iodine is a chemical element with many uses in medicine, depending on the form. Elemental iodine and iodophors are topical antiseptics.[2] Iodine, in non-elemental form, functions as an essential nutrient in human biology (see iodine in biology).[3] Organic compounds containing iodine are also useful iodinated contrast agents in X-ray imaging.[4]

Common side effects when applied to the skin include irritation and discoloration.[2] Supplementation during pregnancy is recommended in regions where deficiency is common, otherwise it is not recommended.[1] Iodine is an essential trace element.[1]

In 1811, Bernard Courtois isolated iodine from seaweed while in 1820 Jean-Francois Coindet linked iodine intake to goiter size.[5] It initially came into use as a disinfectant and a treatment for goiter.[6][7] The following forms of iodine are found on the World Health Organization's List of Essential Medicines:[8]

* Potassium iodide[8]: 18, 42, 43
* Amidotrizoate[8]: 40
* Iohexol[8]: 40
* Meglumine iotroxat[8]: 41
* Povidone iodine[8]: 41
* "Iodine"[8]: 50 - less ambiguously known as iodized oil

In addition, table salt with non-elemental iodine, known as iodized salt, is available in more than 110 countries.[9]

## Forms and formulations

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### Elemental iodine

[edit]

Iodine, elemental

Clinical data
AHFS/Drugs.com| Monograph
License data|

* US DailyMed: Iodine

Routes of
administration| topical
ATC code|

* D08AG03 (WHO)

Legal status
Legal status|

* CA: ℞-only[10]

Identifiers
CAS Number|

* 7553-56-2

UNII|

* 9679TC07X4

Chemical and physical data
Formula| I2

Elemental iodine is used as an antiseptic either as the element, or as the water-soluble triiodide anion I3− generated in situ by adding iodide to poorly water-soluble elemental iodine (the reverse chemical reaction makes some free elemental iodine available for antisepsis).[1]

In the alternative, iodine may be produced from iodophors, 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:[11]

* Tincture of iodine: iodine in ethanol, or iodine and sodium iodide in a mixture of ethanol and water.
* Lugol's iodine: 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, a preparation used in dentistry.
* Povidone iodine (an iodophor).
* Iodine-V: iodine (I2) and fulvic acid form a clathrate compound (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.[12]

The antimicrobial action of iodine is quick and works at low concentrations, and thus it is used in operating theatres.[13] Its specific mode of action is unknown. It penetrates into microorganisms and attacks particular amino acids (such as cysteine and methionine), nucleotides, and fatty acids, ultimately resulting in cell death. It also has an antiviral action, but nonlipid viruses and parvoviruses 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.[14]

### Iodine-containing salts

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As a nutrient, iodine enters cells as the iodide ion;[15] iodide is also the form of iodine found food such as kelp.[16]

The form of iodide salt most commonly used medically is potassium iodide. At low doses, it is one of the options for making iodized salt, along with the more stable potassium iodate. A saturated solution of potassium iodide is used to treat acute thyrotoxicosis. It is also used to block uptake of iodine-131 in the thyroid gland (see isotopes section above), when this isotope is used as part of radiopharmaceuticals (such as iobenguane) that are not targeted to the thyroid or thyroid-type tissues.[17][18]

Iodine-131 (usually as iodide) is a component of nuclear fallout, 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 of order 100 micrograms; see "Dietary Intake" below.) Ingestion of this large dose of non-radioactive iodine minimises the uptake of radioactive iodine by the thyroid gland.[19]

Before the advent of organic chelating agents, salts of iodide were given orally in the treatment of lead or mercury poisoning, such as heavily popularized by Louis Melsens and many nineteenth and early twentieth century doctors.[20][21]

### Organoiodine compounds

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Diatrizoic acid, an iodine-containing radiocontrast agent

As an element with high electron density and atomic number, iodine absorbs X-rays weaker than 33.3 keV due to the photoelectric effect of the innermost electrons.[4] Organoiodine compounds are used with intravenous injection as X-ray radiocontrast agents. This application is often in conjunction with advanced X-ray techniques such as angiography and CT scanning. At present, all water-soluble radiocontrast agents rely on iodine-containing compounds.

* Iohexol (contrast agent)
* Amidotrizoate (contrast agent)
* Meglumine iotroxate (contrast agent)
* Iopanoic acid (contrast agent)

Iodized oil, made by reacting ether esters of fatty acids form vegetable oil with hydroiodic acid, is another important organoiodine preparation. As an iodine supplement, it is given by mouth once per year to prevent endemic goitre in remote communities.[1][22] It is also used as a non-water-soluble radiocontrast.[23]

Other organoiodine drugs include:

* Amiodarone, an antiarrhythmic drug.
* Iodinated glycerol, historically used as a mucolytic.[24]

## See also

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* Isotopes of iodine - lists isotopes with medical uses

## References

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1. ^ a b c d e World Health Organization (2009). Stuart MC, Kouimtzi M, Hill SR (eds.). WHO Model Formulary 2008. World Health Organization. p. 499\. hdl:10665/44053. ISBN 9789241547659.
2. ^ a b "Iodine". The American Society of Health-System Pharmacists. Archived from the original on 13 January 2017. Retrieved 8 January 2017. - This article deals with iodine for topical use. The listed brand names (Iodoflex, Iodosorb) are more appropriately attributed to cadexomer iodine, ATC code D03AX01.
3. ^ "Iodine Deficiency". American Thyroid Association. Archived from the original on 18 November 2022. Retrieved 18 November 2022.
4. ^ a b Lancaster JL. "Chapter 4: Physical Determinants of Contrast" (PDF). Physics of Medical X-Ray Imaging. The University of Texas Health Science Center. Archived from the original (PDF) on 10 October 2015.
5. ^ Leung AM, Braverman LE, Pearce EN (November 2012). "History of U.S. iodine fortification and supplementation". Nutrients. 4 (11): 1740–1746. doi:10.3390/nu4111740. PMC 3509517. PMID 23201844.
6. ^ Starke JA (2009). "14. Application of Iodine Water Purification Tablets: Iodine's Efficacy against Cryptosporidium parvum.". In Preedy VR, Burrow GN, Watson RR (eds.). Comprehensive Handbook of Iodine: Nutritional, Biochemical, Pathological and Therapeutic Aspects. Academic Press. p. 135\. ISBN 9780080920863. Archived from the original on 12 August 2017.
7. ^ Sneader W (2005). "Legacy of the Past". Drug Discovery: A History. John Wiley & Sons. ISBN 9780471899792. Archived from the original on 13 January 2017.
8. ^ a b c d e f g World Health Organization (2019). World Health Organization model list of essential medicines: 21st list 2019. Geneva: World Health Organization. hdl:10665/325771. WHO/MVP/EMP/IAU/2019.06. License: CC BY-NC-SA 3.0 IGO.
9. ^ Wesley AS, Horton S (2010). "Economics of Food Fortification". In Watson RR, Gerald JK, Preedy VR (eds.). Nutrients, Dietary Supplements, and Nutriceuticals: Cost Analysis Versus Clinical Benefits. Springer Science & Business Media. p. 37\. ISBN 9781607613084. Archived from the original on 13 January 2017.
10. ^ "Diagnostic agents". Health Canada. 8 May 2018. Retrieved 13 April 2024.
11. ^ Block SS (2001). Disinfection, sterilization, and preservation. Hagerstwon, MD: Lippincott Williams & Wilkins. p. 159\. ISBN 978-0-683-30740-5.
12. ^ Köntös Z (9 July 2021). "Efficacy of "Essential Iodine Drops" against Severe Acute Respiratory Syndrome-Coronavirus 2 (SARS-CoV-2)". PLOS ONE. 16 (7): e0254341. Bibcode:2021PLoSO..1654341K. doi:10.1371/journal.pone.0254341. PMC 8270147. PMID 34242340.
13. ^ Patwardhan N, Kelkar U (2011). "Disinfection, sterilization and operation theater guidelines for dermatosurgical practitioners in India". Indian Journal of Dermatology, Venereology and Leprology. 77 (1): 83–93. doi:10.4103/0378-6323.74965. PMID 21220895.
14. ^ McDonnell G, Russell AD (January 1999). "Antiseptics and disinfectants: activity, action, and resistance". Clinical Microbiology Reviews. 12 (1): 147–179. doi:10.1128/CMR.12.1.147. PMC 88911. PMID 9880479.
15. ^ Eskin BA, Grotkowski CE, Connolly CP, Ghent WR (July 1995). "Different tissue responses for iodine and iodide in rat thyroid and mammary glands". Biological Trace Element Research. 49 (1): 9–19. doi:10.1007/BF02788999. PMID 7577324. S2CID 24230708.
16. ^ Nagataki S, Shizume K, Nakao K (May 1967). "Thyroid function in chronic excess iodide ingestion: comparison of thyroidal absolute iodine uptake and degradation of thyroxine in euthyroid Japanese subjects". The Journal of Clinical Endocrinology and Metabolism. 27 (5): 638–647. doi:10.1210/jcem-27-5-638. PMID 4164900.
17. ^ "Solubility of KI in water". Hazard.com. 21 April 1998. Retrieved 21 January 2013.
18. ^ "EANM procedure guidelines for 131I-meta-iodobenzylguanidine (131I-mIBG) therapy" (PDF). 17 June 2009. Archived from the original (PDF) on 17 June 2009.
19. ^ "CDC Radiation Emergencies", U.S. Centers for Disease Control, 11 October 2006, accessed 14 November 2010.
20. ^ "Sur l'emploi de l'iodure de potassium pour combattre les affections saturnines et mercurielles", in Annales de chimie et de physique, t. 26, 3e série, 1849.
21. ^ "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.
22. ^ Ingenbleek Y, Jung L, Férard G, Bordet F, Goncalves AM, Dechoux L (November 1997). "Iodised rapeseed oil for eradication of severe endemic goitre". Lancet. 350 (9090): 1542–1545. doi:10.1016/s0140-6736(97)02427-6. PMID 9388412.
23. ^ Olliff J, Riley P (2012). "Radiological contrast agents and radiopharmaceuticals". Side Effects of Drugs Annual. 34: 749–760. doi:10.1016/b978-0-444-59499-0.00046-5. ISBN 978-0-444-59499-0.
24. ^ Petty TL (January 1990). "The National Mucolytic Study. Results of a randomized, double-blind, placebo-controlled study of iodinated glycerol in chronic obstructive bronchitis". Chest. 97 (1): 75–83. doi:10.1378/chest.97.1.75. PMID 2403903.

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