Lugol's iodine

Lugol's iodine, also known as Lugol's solution, first made in 1829, is a solution of elemental iodine and potassium iodide in water, named after the French physician J.G.A. Lugol. Lugol's iodine solution is often used as an antiseptic and disinfectant, for emergency disinfection of drinking water, and as a reagent for starch detection in routine laboratory and medical tests.

It has been used more rarely to replenish iodine deficiency. However, pure potassium iodide, without the more toxic elemental iodine, is preferred for this purpose.

Formula and manufacture

Lugol's solution consists of 5 g iodine (I₂) and 10 g potassium iodide (KI) mixed with 85 ml distilled water, to make a brown solution with a total iodine content of 130 mg/mL. Potassium iodide renders the elementary iodine soluble in water through the formation of the I₃^- ion. It is not to be confused with simple tincture of iodine solutions, which consist of elemental iodine disolved in alcohol. Lugol's solution contains no alcohol.

Other names for Lugol's solution are IKI (Iodine-Potassium Iodide); Iodine, Strong solution (Systemic); Aqueous Iodine Solution BP.

Lugol's is obtained from chemists and pharmacists who are licensed tugjyghjggkghjo prepare and dispense the solution.

Applications

This solution is also used as an indicator to test for the presence of starches in organic compounds, with which it reacts by turning a dark-blue/black. Elemental iodine solutions like Lugol's will stain starches due to iodine's interaction with the coil structure of the polysaccharide. Lugol's solution will not detect simple sugars such as glucose or fructose. In the pathologic condition amyloidosis, amyloid deposits can be so abundant that affected organs will also stain grossly positive for the Lugol reaction for starch.

It can be used as a cell stain, making the cell nuclei more visible and for preserving phytoplankton samples.

During colposcopy, Lugol's iodine is applied to the vagina and cervix. Normal vaginal tissue stains brown due to its high starch content, while tissue suspicious for cancer does not stain, and thus appears pale compared to the surrounding tissue. Biopsy of suspicious tissue can then be performed. This is called a Schiller's test.

Lugol's solution can also be used in various experiments to observe how a cell membrane uses osmosis and diffusion.

Lugol's iodine may also be used as an oxidizing germicide, however it is somewhat undesirable in that it may lead to scarring and discolors the skin temporarily. One way to avoid this problem is by using a solution of 70% ethanol to wash off the iodine later.

Historical applications

Lugol's was often used in the treatment of gout.

It was also used at one time as a first line treatment for severe hypothyroidism due to iodine deficiency in adults.

Historically, Lugol's iodine solution has been widely available and used for a number of health problems with some precautions. Lugol's is sometimes prescribed in a variety of alternative medical treatments.

Until 2007, in the United States of America, Lugol's solution was unregulated and available over the counter as a general reagent, an antiseptic, a preservative, or as a medicament for human or veterinary application.

2007 DEA regulation in the United States

However, effective August 1, 2007, the DEA now regulates Lugol's solution (and, in fact, all iodine solutions containing greater than 2.2% iodine) as a List I precursor because it may potentially be used in the illicit production of methamphetamine. However, transactions of up to one fluid ounce (30 ml) of Lugol's solution are exempt from this regulation. By contrast, Lugol's iodine solution is available over the counter in Canada and Mexico, for example.

See also

• Tincture of iodine
• Betadine

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