Lugol’s iodine

Lugol’s Iodine, also known as Lugol’s Solution, firstmade in 1829, is a solution of elemental iodine andpotassium iodide in water, named after the French physi-cian J.G.A. Lugol. Lugol’s iodine solution is often used asan antiseptic and disinfectant, for emergency disinfectionof drinking water, and as a reagent for starch detection inroutine laboratory and medical tests. These uses are pos-sible since the solution is a source of effectively free ele-mental iodine, which is readily generated from the equi-librium between elemental iodine molecules and triiodideion in the solution.[1]

Lugol’s Solution has been used traditionally to replenishiodine deficiency.[2] Likewise, in the Chernobyl disastersome Lugol’s solution was used as an emergency source ofiodide to block radioactive iodine uptake, simply becauseit was widely available as a drinking water decontaminant,and pure potassium iodide without iodine (the preferredagent) was not available.Since the 1970s Lugol’s Solution has been available intablet form, generally buffered. However, compoundingchemists (pharmacists) had probably been creating tabletscontaining Lugol’s Solution since the early 1900s. Thetablet form is generally known as Iodoral.

1 Applications• As a mordant when performing a Gram stain. It isapplied for 1 minute after staining with crystal vi-olet, but before ethanol to ensure that gram posi-tive organisms’ peptidoglycan remains stained, eas-ily identifying it as a gram positive in microscopy.

• This solution is used as an indicator test for the pres-ence of starches in organic compounds, with whichit reacts by turning a dark-blue/black. Elementaliodine solutions like Lugol’s will stain starches dueto iodine’s interaction with the coil structure of thepolysaccharide. Starches include the plant starchesamylose and amylopectin and glycogen in animalcells. Lugol’s solution will not detect simple sugarssuch as glucose or fructose. In the pathologic con-dition amyloidosis, amyloid deposits (i.e., depositsthat stain like starch, but are not) can be so abun-dant that affected organs will also stain grossly pos-itive for the Lugol reaction for starch.

• It can be used as a cell stain, making the cell nu-clei more visible and for preserving phytoplanktonsamples.

• During colposcopy, Lugol’s iodine is applied to thevagina and cervix. Normal vaginal tissue stainsbrown due to its high glycogen content, while tis-sue suspicious for cancer does not stain, and thusappears pale compared to the surrounding tissue.Biopsy of suspicious tissue can then be performed.This is called a Schiller’s test.

• Lugol’s iodine may also be used to better visualizethe mucogingival junction in the mouth. Similar tothe method of staining mentioned above regardinga colposcopy, alveolar mucosa has a high glycogencontent that gives a positive iodine reaction vs. thekeratinized gingiva.[3]

• Lugol’s solution can also be used in various experi-ments to observe how a cell membrane uses osmosisand diffusion.

• Lugol’s iodine may also be used as an oxidizinggermicide, however it is somewhat undesirable inthat it may lead to scarring and discolors the skintemporarily. One way to avoid this problem is byusing a solution of 70% ethanol to wash off the io-dine later.

• Lugol’s solution is also used in the marine aquar-ium industry. Lugol’s solution provides a strongsource of free iodine and iodide to reef inhabitantsand macroalgae. Although the solution is thoughtto be effective when used with stony corals, systemscontaining xenia and soft corals are assumed to beparticularly benefited by the use of Lugol’s solution.Used as a dip for stony and soft or leather corals,Lugol’s may help rid the animals of unwanted par-asites and harmful bacteria. The solution is thoughtto foster improved coloration and possibly preventbleaching of corals due to changes in light intensity,and to enhance coral polyp expansion. The blue col-ors of Acropora spp. are thought to be intensifiedby the use of potassium iodide. Specially packagedsupplements of the product intended for aquariumuse can be purchased at specialty stores and online.

• Preoperative administration of Lugol’s solu-tion decreases intraoperative blood loss duringthyroidectomy in patients with Grave’s disease.[4]However, it appears ineffective in patients whoare already euthyroid on anti-thyroid drugs andlevothyroxine.[5]

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2 6 REFERENCES

2 Historical applications

Lugol’s was often used in the treatment of gout.It was also used at one time as a first line treatment forhyperthyroidism, as the administration of pharmacologicamounts of iodine leads to temporary inhibition of iodineorganification in the thyroid gland, a phenomenon calledthe Wolff-Chaikoff effect. However it is not used to treatcertain autoimmune causes of thyroid disease as iodine-induced blockade of iodine organification may result inhypothyroidism. They are not considered as a first linetherapy because of possible induction of resistant hyper-thyroidism but may be considered as an adjuvant therapywhen used together with other hyperthyrodism medica-tions.Because of its wide availability as a drinking-water de-contaminant, and high content of potassium iodide, emer-gency use of it was at first recommended to the Polishgovernment in 1986, after the Chernobyl disaster to re-place and block any intake of radioactive 131I, even though it was known to be a non-optimal agent,due to its somewhat toxic free-iodine content.[6] Othersources state that pure potassium iodide solution in wa-ter (SSKI) was eventually used for most of the thyroidprotection after this accident.[7] There is “strong scien-tific evidence” for potassium iodide thyroid protection tohelp prevent thyroid cancer. Potassium iodide does notprovide immediate protection but can be a component ofa general strategy in a radiation emergency.[8]

Historically, Lugol’s iodine solution has been widelyavailable and used for a number of health problems withsome precautions.[9] Lugol’s is sometimes prescribed ina variety of alternative medical treatments.[10][11] Onlysince the end of the Cold War has the compound becomesubject to national regulation in the Anglosphere.

3 National Regulation

Until 2007, in the United States, Lugol’s solution wasunregulated and available over the counter as a generalreagent, an antiseptic, a preservative,[12] or as a medica-ment for human or veterinary application.However, effective August 1, 2007, the DEA now reg-ulates Lugol’s solution (and, in fact, all iodine solutionscontaining greater than 2.2% iodine) as a List I precursorbecause it may potentially be used in the illicit produc-tion of methamphetamine.[13] However, transactions ofup to one fluid ounce (30 ml) of Lugol’s solution are ex-empt from this regulation. When buying Lugol’s Solutionon places like Amazon, most sellers fail to indicate theDEA tracking requirement. On the other hand Lugol’sIodine solution is available over the counter in Canadaand Mexico.

4 Toxicity

Because it contains free iodine, Lugol’s solution at 2%or 5% concentration without dilution is irritating and de-structive to mucosa, such as the lining of the esophagusand stomach.Doses of 10 mL of undiluted 5% solution havebeen reported to cause gastric lesions when used inendoscopy.[14] The LD50 for Iodine is 14,000 mg/kg[Rat] and 22,000 mg/kg [Mouse].[15]

Most guidelines accept that anything with an LD50 >2g/kg (or 3-5 g/kg in some countries) can be classed ashaving a low acute toxicity which classifies Iodine ashaving low toxicity. Potassium Iodide is not consideredhazardous.[16]

5 See also

General topic

• Antiseptic

Forms of Iodine

• Betadine

• Cadexomer iodine

• Chlorhexidine

• Iodophor

• Inadine

• Povidone-iodine

• Tincture of iodine

Reagents

• Benedict’s reagent

• Melzer’s reagent

• Verhoeff’s Stain

6 References[1] Turner, Douglas; Flynn, George; Sutin, Norman; Beitz,

James (March 1972). “Laser Raman temperature-jump study of the kinetics of the triiodide equilib-rium. Relaxation times in the 10-8 −10-7 secondrange”. J. Am. Chem. Soc. 94 (5): 1554–1559. doi:10.1021/ja00760a020. Retrieved 16 Novem-ber 2015.

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[2] Higdon, J. (April, 2003) “Micronutrient Information Cen-ter: Iodine,” Linus Pauling Institute/Oregon State Univer-sity (revised by Drake, V.J., July, 2007).

[3] Han, J. Changes in Gingival Dimensions Following Con-nective Tissue Grafts for Root Coverage: Comparison ofTwo Procedures. J Perio 2008;79:1346-1354.

[4] Erbil Y, Ozluk Y, Giriş M, et al. (June 2007). “Effect oflugol solution on thyroid gland blood flow and microvesseldensity in the patients with Graves’ disease”. J. Clin. En-docrinol. Metab. 92 (6): 2182–9. doi:10.1210/jc.2007-0229. PMID 17389702.

[5] Kaur S, Parr JH, Ramsay ID, Hennebry TM, Jarvis KJ,Lester E (May 1988). “Effect of preoperative iodine inpatients with Graves’ disease controlled with antithyroiddrugs and thyroxine”. Ann R Coll Surg Engl 70 (3): 123–7. PMC 2498739. PMID 2457351.

[6] Rotkiewicz, Marcin; Henryk Suchar; Ryszard Kamiñski(14 January 2001). “Chernobyl: the Biggest BLUFF ofthe 20th Century”. Polish weekly Wprost. pp. no 2. Re-trieved 2008-06-18.

[7] US FDA, “Potassium Iodide as a Thyroid Blocking Agentin Radiation Emergencies,” U.S. Department of Healthand Human Services Food and Drug Administration Cen-ter for Drug Evaluation and Research (CDER); Decem-ber, 2001.

[8] “Iodine.” MedlinePlus.

[9] Drugs.com, “Lugol’s Solution”

[10] Optimox.com, “Iodine”

[11] Jcrows.com, “Iodine”

[12] Hawkins; et al. (2005). “Change in cyanobacterial bio-volume due to preservation by Lugol’s Iodine”. HarmfulAlgae 4 (6): 1033–1043. doi:10.1016/j.hal.2005.03.001.

[13] US DEA, “Final Rule: Changes in the Regulation of Io-dine Crystals and Chemical Mixtures Containing Over 2.2Percent Iodine” (July 2, 2007) Federal Register, Volume72, Number 126 (FR Doc E7-12736)

[14] Sreedharan et al. (June 2005). “Acute toxic gas-tric mucosal damage induced by Lugol’s iodine sprayduring chromoendoscopy”. Gut 54 (6): 886–887.doi:10.1136/gut.2004.061739. PMC 1774547. PMID15888800.

[15] Sciencelab.com

[16] Esciencelabs.com

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