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Iodine

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Iodine (I)

Background

Iodine is an element (atomic number 53), which is required by humans for the synthesis of thyroid hormones (triiodothyronine/T3 and thyroxine/T4).

Chronic iodine deficiency can lead to numerous health problems in children and adults, including thyroid gland dysfunction (including goiter) and various neurologic, gastrointestinal, and skin abnormalities. Iodine deficiency in pregnant or nursing mothers can lead to significant neurocognitive deficits in their infants. "Cretinism" or severe mental retardation is a rare outcome of severe iodine deficiency during early development. Growth stunting, apathy, impaired movement, or speech/hearing problems may occur. Many individuals living in developing countries may be at risk of iodine deficiency and its complications, and iodine deficiency is considered to be a preventable cause of mental retardation.

Iodine deficiency is rare in industrialized countries such as the United States, due to enrichment of table salt and cattle feed with iodine. But deficiency is common in developing countries, where supplementation may be considered.

Humans obtain iodine from their diets. The amount of iodine in food or water depends upon the amount of iodine in the local soil. Areas with mountainous (glacier) water or heavy rainfall tend to be low in iodine content, increasing the risk of iodine deficiency.

This review does not discuss medical uses of radioactive iodine or iodine contrast agents used for imaging studies such as computerized tomography (CT scanning).

Synonyms

Atomic number 53, Betadine®, cadexomer iodine, I, Iodin, iodine-125, iodine-131, iodized poppy seed oil, iodized salt, iodothyronine, iodotyrosine, KI, Licartin, Lipiodol®, Lugol solution, potassium iodide (KI), polyvinylpyrrolidone-iodine, povidone-iodine, PVP-I, radioiodine, SKI, strong iodine, tincture of iodine.

Note: This review does not discuss medical uses of radioactive iodine or iodine contrast agents used for imaging studies such as computerized tomography (CT scanning).

Evidence

These uses have been tested in humans or animals. Safety and effectiveness have not always been proven. Some of these conditions are potentially serious, and should be evaluated by a qualified healthcare provider.

Uses based on scientific evidence	Grade^*
Goiter prevention Iodine deficiency is one of the causes of goiter (hypertrophy of the thyroid gland as it tries to make more thyroid hormone in the absence of iodine). Physically, goiter appears as an abnormal enlargement of the thyroid gland in the neck. Other causes of goiter include autoimmune thyroiditis, excess iodine, other hormonal disorders, radiation exposure, infectious causes, or inborn errors of metabolism. Although goiter due to low iodine intake is rare in developed countries, it may occur in regions with endemic low iodine levels. To avoid iodine deficiency in the United States, table salt is enriched with iodine ("iodized" salt), and iodine is added to cattle feed and used as a dough conditioner. Iodine supplementation is generally not recommended in developed countries where sufficient iodine intake is common, and excess iodine can actually cause medical complications (including goiter).Iodine supplementation should be considered in cases of known iodine deficiency, and should be administered with medical supervision if possible. Notably, the treatment of goiter usually involves administration of thyroid hormone, most commonly levothyroxine sodium (Synthroid®, Levoxyl®, Levothroid®). Iodine generally does not play a role in the acute management of this condition.	A
Iodine deficiency In regions with low iodine intake or cases of known deficiency, iodine enrichment of foods or supplementation should be considered. To avoid iodine deficiency in the United States, table salt is enriched with iodine ("iodized" salt), and iodine is added to cattle feed and used as a dough conditioner. Iodine deficiency is uncommon in developed countries, but is common in other parts of the world. When considering iodine enrichment or supplementation, supervision by medical personnel or public health officials is recommended due to the potential complications involved with iodine replacement in the setting of previous deprivation, particularly if considering supplementation in pregnant women or children.	A
Radiation emergency (potassium iodide thyroid protection) Potassium iodide (KI) can be taken in the setting of radiation exposure in order to reduce levels of radioactive iodine uptake by the thyroid, thus reducing the risk of later development of thyroid cancer. It is important to note that KI does not provide immediate protection from radiation damage, and does not have protective effects against other complications of radiation exposure. KI can serve as a part of a general strategy in cases of radiation emergencies, in conjunction with shelter and control of foodstuffs. Many radiation emergency kits include KI.	A
Skin disinfectant/sterilization Iodine is commonly used in topical disinfectant preparations for cleaning wounds, sterilizing skin before surgical/invasive procedures, or sterilizing catheter entry sites. Betadine solution, for example, contains povidone-iodine. Other topical disinfectants include alcohol and antibiotics, and iodine is sometimes used in combination with these. Commercially prepared iodine products are recommended in order to assure appropriate concentrations.	A
Water purification Iodine can be used as an antimicrobial agent for the emergency purification of water. Tablets and solutions are commercially available. Effects generally occur within 15 minutes.	A
Bacterial conjunctivitis Povidone-iodine solutions have been used in the management of childhood bacterial conjunctivitis, and may be as effective as other anti-bacterial solutions such as neomycin-polymyxin B-gramicidin. This is not an effective treatment for viral conjunctivitis. Medical supervision is recommended.	B
Graves disease (adjunct iodine/iodides) Graves disease is an immune-mediated disorder that causes hyperthyroidism. Thyroid-stimulating immunoglobulins bind to the thyroid stimulating hormone (TSH) receptor and mimic the action of thyroid TSH, and stimulate thyroid growth and thyroid hormone overproduction. Standard treatments for Graves disease target the thyroid gland (rather than the source of the disorder), and include antithyroid drugs such as propylthiouracil or methimazole, radioactive iodine to ablate (destroy) thyroid cells, or surgery to remove thyroid tissue. Beta-blocker drugs may be used to control symptoms. Iodide preparations can be used to suppress thyroid hormone release from the thyroid, such as strong iodine solution (Lugol solution), potassium iodide (SSKI), and iodinated radiographic contrast agents (sodium ipodate). Patients undergoing thyroid surgery are commonly treated preoperatively with antithyroid drugs to achieve a euthyroid state, then SSKI.	B
Hearing loss (iodine deficiency) Auditory disturbances may be present in iodine deficient children, and continuous iodine supplementation may improve the auditory thresholds.	B
Ocular surgery infection prevention / cataract surgery antisepsis Topical iodine solutions such as povidone-iodine are used preoperatively to sterilize prior to ophthalmologic procedures. For example, povidone-iodine solution has been studied and used preoperatively for cataract surgery antisepsis.	B
Ophthalmia neonatorum prevention "Ophthalmia neonatorum" is defined as conjunctivitis with eye discharge that occurs during the first month of life. Various bacteria can cause this condition, including gonococcus and Chlamydia trachomatis . Several agents have been used as drops in the eyes to prevent this condition in infants, including erythromycin, silver nitrate, gentamicin, and povidone-iodine. Tetracycline and penicillin drops have also been used. Although this condition is now uncommon in industrialized nations, it remains a problem in the developing world with an incidence as high as 20-30% and cases of blindness reported in Africa each year.Povidone-iodine ophthalmic solution appears to have broad-spectrum activity against bacteria, and is less expensive than many antibiotics. It therefore may be a cost-effective option in some populations.	B
Oral mucositis There is limited research to suggest that iodine mouth rinses may decrease the severity of mucositis in the mouth related to cancer chemotherapy or radiation therapy. The management of mucositis should be discussed with the cancer care team.	B
Thyrotoxicosis / thyroid storm (adjunct iodides) Hyperthyroid crisis (thyroid storm) is a medical emergency caused by excessive release of thyroid hormones into the circulation. Initial management of this condition involves inhibition of thyroid function with thioamide drugs such as propylthiouracil or methimazole. Iodides (such as potassium iodide) can then be administered to block the release of thyroid hormone, but should only be given an hour after thioamides to assure that the iodide is not used by the thyroid to make more thyroid hormone and worsen symptoms. Caution is warranted, because iodide preparations carry a risk of causing serum sickness. Iodides should not be used for long-term treatment of thyrotoxicosis.	B
Bladder irrigation Povidone-iodine bladder irrigation has been suggested prior to catheter removal, or prior to prostatectomy surgery, to reduce the risk of infection. There is limited research in this area.	C
Bowel irrigation Povidone-iodine irrigation before large bowel resection has been suggested as a sterilization technique.	C
Cancer The potential role of non-radioactive iodine in cancer care remains unknown. Antioxidant and anti-tumor effects have been proposed based on laboratory research. In contrast, some scientists have asserted that tumors may uptake more iodine than normal tissues. It has been suggested that high rates of gastric (stomach) cancer or low rates of breast cancer in coastal Japan may be due to high iodine intake, although this has not been demonstrated scientifically. Povidone-iodine solutions have been used as a part of alternative cancer regimens, such as the Hoxsey formula. Preliminary study has also indicated povidone-iodone solution as a potential rectal washout for rectal cancer. Overall, no clear conclusion can be drawn based on the currently available evidence.	C
Cognitive function Iodine is required for the production of thyroid hormones, which are necessary for normal brain development and cognition. One study showed that oral iodized oil significantly improved performance on cognitive tests in 10-12 year-old school children. Further study is needed to confirm these results.	C
Corpus vitreous degeneration Topical administration of iodine eye drops may reduce corpus vitreous degeneration. Further study is needed to confirm these results.	C
Goiter treatment Iodine deficiency can cause goiter (hypertrophy of the thyroid gland). Other causes of goiter should be considered in patients with this condition, such as autoimmune thyroiditis, excess iodine, other hormonal disorders, radiation exposure, infectious causes, or inborn errors of metabolism. Although goiter due to low iodine intake is rare in developed countries, it may occur in regions with endemic low iodine levels.Initial management of goiter should involve a medical evaluation to identify the underlying cause, and assessment of levels of thyroid hormones in the body. Treatment usually involves administration of thyroid hormone, most commonly levothyroxine sodium (Synthroid, Levoxyl, Levothroid). Iodine plays a role in goiter prevention, but not in acute management of this condition. Iodine deficiency should be corrected if found, with supplementation.	C
Lymphedema (filarial) Footcare with betadine may help in the management of filarial lymphoedema.	C
Molluscum contagiosum Povidone-iodine has been suggested as a topical treatment for molluscum. There is limited research in this area.	C
Oral intubation Gargling with povidone-iodine before oral intubation reduces the transport of bacteria into the trachea.	C
Pelvic infection Vaginal douching with aqueous povidone iodine followed by normal saline irrigation immediately before oocyte retrieval seems effective in preventing the pelvic infection without compromising the outcome of in vitro fertilization treatment.	C
Periodontitis / gingivitis Povidone-iodine mouthwash has been suggested to reduce mouth flora in the setting of periodontitis or around oral surgery. Evidence in this area is not conclusive.	C
Pneumonia Based on one prospective randomized study regular oropharyngeal application of povidone-iodine may decrease the prevalence of ventilator-associated pneumonia in patients with severe head trauma. Evidence in this area is not conclusive.	C
Postcesarean endometritis Preoperative vaginal scrub with povidone-iodine decreases the incidence of postcesarean endometritis. This intervention does not seem to decrease the overall risk of postoperative fever or wound infection.	C
Renal Pelvic Instillation Sclerotherapy (RPIS) Povidone iodine 0.2% has been shown to be as effective for RPIS as 1% silver nitrate.	C
Wound healing It is not clear if healing of wounds or skin ulcers is improved with the application of topical iodine solutions. Iodine solutions may assist with sterilization as a part of a larger approach to the healing process.	C
Visual outcomes in corneal ulceration The addition of povidone-iodine to standard antibiotic therapy did not improve visual outcomes in corneal ulceration patients in one study.	D

*Key to grades

A: Strong scientific evidence for this use;

B: Good scientific evidence for this use;

C: Unclear scientific evidence for this use;

D: Fair scientific evidence against this use;

F: Strong scientific evidence against this use.

Grading rationale

Uses based on tradition or theory

The below uses are based on tradition or scientific theories. They often have not been thoroughly tested in humans, and safety and effectiveness have not always been proven. Some of these conditions are potentially serious, and should be evaluated by a qualified healthcare provider.

Anemia,Ascaris lumbricoides, burn wound healing, chronic otitis media, circulation enhancement, cutaneous sporotrichosis, dendritic keratitis, diabetic foot ulcers, energy level enhancement, fibrocystic breast disease, hookworm, hyperlipidemia,infant mortality improvement, Kashin-Beck osteoarthropathy, keratoconjuctivitis, renal impairment, respiratory congestion, thyroid adenoma,Trichuris trichiura,Schistosoma mansoni, vaginitis, venous leg ulcers, weight loss, wound infection.

Dosing

The below doses are based on scientific research, publications, traditional use, or expert opinion. Many herbs and supplements have not been thoroughly tested, and safety and effectiveness may not be proven. Brands may be made differently, with variable ingredients, even within the same brand. The below doses may not apply to all products. You should read product labels, and discuss doses with a qualified healthcare provider before starting therapy.

Adults (18 years and older):

U.S. Recommended Daily Allowance (RDA): 150 micrograms daily in adults ages 18 and older (220 micrograms daily for pregnant women, 290 micrograms daily for breastfeeding women).

Tolerable Upper Intake Levels (UL): For adults ages 18 and older, 1,100 micrograms daily.

Cataract surgery antisepsis: 1% povidone-iodine solution used preoperatively. Eye drops containing 0.8% povidone-iodine solution have been used three times every five minutes prior to surgery.

Chronic suppurative otitis media: 5% povidone-iodine ear drops, three drops taken three times daily for 10 days has been used, although other approaches such as antibiotics should be considered and discussed with a supervising healthcare professional.

Goiter: In those with goiter induced by iodine deficiency, correction may not be practical, and treatment should involve thyroid hormone replacement with levothyroxine sodium (Synthroid, Levoxyl, Levothroid). If practical, iodine deficiency can be corrected, although iodine deficiency is rare in industrialized countries due to supplementation of table salt and cattle feed with iodine. See above dosing for iodine deficiency. Other causes of goiter should also be considered, under the supervision of a licensed healthcare professional. For endemic goiter, 400 micrograms of iodine dialy as di-iodotyrosine has been used, or 150 micrograms iodine/500 micrograms iodide with levothyroxine has been used. For gestational goiter, under medical supervision, doses of 50-200 micrograms of iodide daily has been used.

Hyperthyroidism, Graves disease, thyroid storm: As an adjunct to prescription drug inhibitors of thyroid function (such as propylthiouracil or methimazole), saturated solution of potassium iodide (SSKI, PIMA) 1-5 gtt by mouth every 8 hours, or Lugol solution (8 milligrams iodide per drop) 2-6 gtt (1 milliliter) every 8 hours has been used. For thyrotoxicosis, parenteral treatment may be used, and sodium iodide 1 gram by slow intravenous drip every 8-12 hours has been given. Management should be under the supervision of a licensed healthcare professional. Lower doses may be used in pregnancy.

Iodine deficiency: Iodine deficiency is rare in industrialized countries due to supplementation of table salt and cattle feed with iodine. In areas of endemic iodine deficiency, various doses of iodine have been used as prevention or treatment, including 200 milligrams or 2 milliliters of iodized oil daily by mouth. For prolonged supplementation, a single annual intramuscular injection with 1 milliliter Lipiodol UF (480 milligrams of iodine) or 570 milligrams of oral iodine has been used. In those with goiter induced by iodine deficiency, correction may not be practical, and treatment should involve thyroid hormone replacement with levothyroxine sodium (Synthroid, Levoxyl, Levothroid).

Mouthwash: As an antibacterial mouthwash, 10-20 milliliters of povidone-iodine mouthwash has been used as a rinse and gingival sulcus irrigant. For prevention of plaque and gingivitis, mouth rinses have been used up to twice daily. For chemotherapy mucositis prevention, povidone-iodine rinses have been used up to four times daily.

Pneumonia: 20 milliliters of a 10% povidone-iodine aqueous solution, reconstituted in a 60 milliliters solution with sterile water has been used as a nasopharynx and oropharynx rinse in patients with pneumonia and head trauma.

Preoperative before thyroidectomy: Lugol solution 5-10 gtt three times daily, or 2-6 gtt twice or three times daily given 10-21 days prior to surgery has been used. Use for longer than 14 days can lead to "iodide escape" with rebound thyrotoxicosis, and should be avoided. In pregnant women there is a risk of fetal goiter, although brief administration of lower doses (6-40 milligrams per day) can be considered. Potassium iodide (SSKI, PIMA) 1-2 gtt three times daily mixed in juice or water has also been given. Administration of these preparations should be under the direction of the operating surgeon.

Radiation emergencies: Potassium iodide (KI) should be taken just prior to, or as soon as possible after exposure. For adults exposed to 10 centigrays (cGy) of radiation or more, KI 130 milligrams is given (for pregnant or lactating women, 120 milligrams KI is administered for radiation exposure of 5cGy or more).

Skin/wound sterilization: Various concentrations of iodine have been used, for example 2% tincture or 2% aqueous solution to affected areas; 10% povidone-iodine applied prior to insertion of catheters; 0.9% iodine ointment for diabetic foot ulcers; and 1% povidone-iodine for wound irrigation. Use as directed.

Upper airway sterilization: 1% povidone-iodine solution inhaled via nebulizer twice daily has been used, with gargle twice daily.

Water sterilization: Salt iodization of water supplies on a large-scale basis can be performed with the addition of iodide or iodate salt with an iodine content varying from 7-100 milligrams per kilogram of salt. For individual use, tincture of iodine 3-10 drops per quart of water has been used, with 15 minutes for anti-microbial effects to occur.

Children (younger than 18 years):

Recommended Daily Allowance (RDA): 50 micrograms daily for infants 0-12 months; 90 micrograms daily for 1-8 years; 120 micrograms daily for 9-13 years; 150 micrograms daily for 14-18 years.

Adequate Intake (AI) for infants: 110 micrograms daily for ages 0-6 months; 130 micrograms daily for 7-12 months.

Tolerable Upper Intake Levels (UL): 200 micrograms per day for ages 1-3 years; 300 micrograms per day for 4-8 years; 600 micrograms per day for 9-13 years; 900 micrograms per day for 14-18 years (including pregnancy and lactation).

Ophthalmia neonatorum prevention: 1 drop of 2.5% povidone-iodine applied at birth has been used. No advantage of a second drop has been found.

Radiation emergencies: Potassium iodide (KI) should be taken just prior to, or as soon as possible after exposure. For infants, babies, and children, KI is administered for exposure of 5 centigrays (cGy) or more. For birth through one month, 16 milligrams can be administered; for one month through three years, 32 milligrams can be administered; for 3-12 years, 65 milligrams can be administered; for adolescents ages 12-18 years, 65 milligrams can be administered (or up to 120 milligrams if the adolescent is approaching adult size).

Skin/wound sterilization: Various concentrations of iodine have been used, for example 2% tincture or 2% aqueous solution to affected areas.

Thyroid disorders: Children should be managed under medical supervision.

Safety

The U.S. Food and Drug Administration does not strictly regulate herbs and supplements. There is no guarantee of strength, purity or safety of products, and effects may vary. You should always read product labels. If you have a medical condition, or are taking other drugs, herbs, or supplements, you should speak with a qualified healthcare provider before starting a new therapy. Consult a healthcare provider immediately if you experience side effects.

Allergies

Some individuals are allergic/hypersensitive to iodide or to organic preparations containing iodine. Hypersensitivity reactions may involve rash, angioedema (throat swelling), cutaneous/mucosal hemorrhage (bleeding), fever, arthralgias (joint pains), eosinophilia (abnormal blood counts), urticaria (hives), thrombotic thrombocytopenic purpura, or severe periarteritis (inflammation around blood vessels). Reactions can be severe and deaths have occurred with exposure. Iodine-based products should be avoided if there is known allergy/hypersensitivity to iodine.

Topical use of iodine preparations may irritate/burn tissues and cause sensitization in some individuals.

This review does not comprehensively cover the use of iodine-based intravenous contrast media for CT scan imaging, although serious life-threatening allergic reactions have been associated with use. Individuals with known or suspected iodine hypersensitivity should inform their physician prior to receiving contrast media.

Notes:

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EditText of this page (last edited February 14, 2008)