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Iodine (I)

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Also listed as: Povidone-iodine, Betadine
Related terms
Background
Evidencetable
Tradition
Dosing
Safety
Interactions
Attribution
Bibliography

Related Terms
  • 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, Lugol's iodine, PI, polyvinylpyrrolidone-iodine, potassium iodide, povidone-iodine, PVP-I, radioiodine, SKI, strong iodine, tincture of iodine.
  • Note: This review does not discuss the medical uses of radioactive iodine or iodine contrast agents for imaging studies such as computerized tomography (CT scanning).

Background
  • Iodine is an element (atomic number 53) that is required by humans for the synthesis of thyroid hormones (triiodothyronine and thyroxine, or T3 and T4, respectively).
  • 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 or 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 the enrichment of table salt and cattle feed with iodine. But deficiency is common in developing countries, where a supplementation program may be considered useful.
  • 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.
  • Iodine has antimicrobial properties and is commonly used as a topical antiseptic.
  • This review does not discuss medical uses of radioactive iodine or iodine contrast agents for imaging studies such as computerized tomography (CT scanning).

Evidence Table

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. GRADE *


Iodine is commonly used in topical disinfectant preparations for cleaning wounds, sterilizing skin before surgical or 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. Iodine is also used as a surgical hand scrub and to disinfect medical equipment. Commercially prepared iodine products are recommended in order to assure appropriate concentrations. Iodine can be used as an antimicrobial agent for the emergency purification of water. Tablets and solutions are available. Effects generally occur within 15 minutes.

A


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. 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 the 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


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. While iodine deficiency is not common in developed countries, it 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 after previous deprivation, particularly if considering supplementation in pregnant women or children.

A


Iodine-131 is a component of nuclear fallout and is dangerous because the thyroid gland concentrates ingested iodine. Nonradioactive potassium iodide (KI) tablets may be taken by individuals at risk for 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


Iodine is required for the production of thyroid hormones, which are necessary for normal brain development and cognition. In children, prolonged iodine deficiency leads to learning disabilities, a lower intelligence quotient (IQ), and poor motivation to achieve. There is evidence that iodine supplementation improves perceptual reasoning, information processing, fine motor skills, and visual problem solving in iodine-deficient children. For this reason, it is important for pregnant and lactating women, as well as children, to have sufficient iodine intake.

B


Povidone-iodine solutions have been used in the management of childhood bacterial conjunctivitis (pinkeye) and may be as effective as other antibacterial solutions such as neomycin-polymyxin B-gramicidin. A combination of povidone-iodine and dexamethasone has been used to treat adenoviral conjunctivitis. It turns the surface of the eye brown for a few minutes. Medical supervision is advised.

B


Fibrocystic breast disease is a benign form of iodine deficiency characterized by lumpy, painful breasts and palpable fibrosis. Iodine supplementation has reduced pain and other symptoms associated with this condition.

B


Graves' disease is an immune-mediated disorder that causes hyperthyroidism. Thyroid-stimulating immunoglobulins bind to the thyroid-stimulating hormone (TSH) receptor, 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), saturated solution of 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 (normal) state, then with SSKI.

B


Auditory disturbances may be present in iodine-deficient children. Continuous iodine supplementation may improve the auditory thresholds.

B


Topical iodine solutions, such as povidone-iodine, are used preoperatively for sterilization prior to ophthalmologic procedures. For example, povidone-iodine solution has been studied and used as an antiseptic before cataract surgery.

B


Ophthalmia neonatorum is 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


Povidone-iodine mouthwash has been suggested to reduce mouth flora from periodontitis or around oral surgery. There is evidence that the use of povidone-iodine during scaling and root planning (deep cleaning performed by a dentist or dental hygienist) reduces the depth of gum pockets where cavities may form.

B


Post-Cesarean endometritis occurs when uterine tissue starts to grow at the incision site following a Cesarean section. Preoperative vaginal scrub with povidone-iodine solution immediately before Cesarean delivery reduces the risk of postoperative endometritis, especially for women undergoing Cesarean delivery with ruptured membranes. This intervention does not seem to decrease the overall risk of postoperative fever or wound infection.

B


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 they 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


Povidone-iodine bladder irrigation has been suggested prior to catheter removal, or prior to prostatectomy surgery, to reduce the risk of infection. Research in this area is limited.

C


Early research suggests that povidone-iodine may control bleeding during dental surgery better than saline. Additional research is needed before a conclusion can be made.

C


Povidone-iodine irrigation before large bowel resection has been suggested as a sterilization technique. Further study is warranted.

C


The potential role of nonradioactive iodine in cancer care remains unknown. Antioxidant and antitumor 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 research has also indicated povidone-iodine solution as a potential rectal washout for rectal cancer. Iodine use has been linked to a decrease in prostate and stomach cancers in some populations. Overall, no clear conclusion can be drawn based on the currently available evidence.

C


Topical administration of iodine eye drops may reduce corpus vitreous degeneration. Further research is needed to confirm these results.

C


In patients with early childhood caries, povidone-iodine treatment reduced the risk of further cavities developing. Further studies in this area are warranted.

C


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 the 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 with iodine supplementation, if found.

C


Kashin-Beck disease is an osteoarthropathy found in selenium- and iodine-deficient areas. Iodine supplementation may be effective in the prevention and treatment of this condition. Further research in this area is needed.

C


Iodine has been suggested as a possible treatment for kidney cysts, which are small, fluid-filled sacs in the kidneys. There is conflicting evidence in this area. Further research is needed.

C


Footcare with Betadine® may help in the management of filarial lymphedema. More research is needed in this area.

C


Molluscum contagiosum is a common skin infection that is caused by a pox virus. Povidone-iodine has been suggested as a topical treatment for molluscum. Research in this area is limited.

C


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 patient's cancer care team.

C


Limited evidence shows that gargling with povidone-iodine before oral intubation (opening airways with a tube) reduces the transport of bacteria into the trachea. More research is needed in this area.

C


Vaginal douching with aqueous povidone-iodine followed by normal saline irrigation immediately before egg cell retrieval seems effective in preventing pelvic infection, without compromising the outcome of in vitro fertilization treatment. There is evidence that the application of povidone-iodine vaginal gel at the beginning of abdominal hysterectomy may prevent infection.

C


There is limited evidence that regular oropharyngeal (in the mouth and pharynx) 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 at this time.

C


There is limited evidence that povidone-iodine is as effective as 1% silver nitrate for RPIS. More research is needed in this area.

C


Rinsing with povidone-iodine before dental procedures may help reduce the incidence and severity of bacterial infections of the blood. More research is needed in this area.

C


Routine iodine supplementation may be useful for preventing recurrent nodular thyroid disease in patients from iodine-deficient regions. More research is needed in this area.

C


Antibiotic therapy with povidone-iodine does not seem to improve visual outcomes in corneal ulceration. The effects of povidone-iodine alone are not clear.

C


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. Further research in this area is needed.

C


Iodine is essential for the production of thyroid hormones, which are needed for brain development in newborns. Preterm infants often have low levels of iodine and thyroid hormones in the first few weeks after birth. Infant formula and human breast milk contain insufficient iodine to meet recommended intakes for preterm infants. However, there is limited evidence suggesting that dietary supplementation with iodine does not benefit preterm infants.

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 for this use (it may not work)
F: Strong scientific evidence against this use (it likley does not work)


Tradition / Theory

The below uses are based on tradition, scientific theories, or limited research. 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. There may be other proposed uses that are not listed below.

  • Anemia, antifungal (cutaneous sporotrichosis), blood circulation improvement, burn wound healing, cardiovascular disease, chronic otitis media, cyclic mastalgia (breast pain), diabetes, diabetic foot ulcers, energy level enhancement, fungal skin infections, hyperlipidemia immune enhancement, infant mortality improvement, keratitis, keratoconjuctivitis, parasites, respiratory congestion, thyroid adenoma, vaginitis, venous leg ulcers, weight loss.

Dosing

Adults (18 years and older)

  • The U.S. recommended dietary allowance (RDA) for iodine is 150 micrograms daily in adults aged 18 and older, 220 micrograms daily for pregnant women, and 290 micrograms daily for breastfeeding women. The tolerable upper intake levels (UL) for adults aged 18 and older is 1,100 micrograms daily.
  • As an antimicrobial to reduce surgical site infections, a 0.35%, 1%, and/or 10% povidone-iodine irrigation or a 5% povidone-iodine spray has been used. As a preoperative skin antiseptic, 0.75-10% povidone-iodine with or without 74% isopropyl alcohol applied 1-2 times prior to surgery has been used. No difference in effectiveness was found among povidone-iodine aqueous hand scrubs of different durations (varying from two minutes to five minutes). 0.9% iodine ointment has been used for diabetic foot ulcers.
  • For bleeding, irrigation of tooth extraction sockets with povidone-iodine (1% w/v) stopped bleeding.
  • For bowel irrigation, a 10% aqueous solution of povidone-iodine (Betadine®) irrigation effectively reduced wound sepsis in patients undergoing major resection for large bowel carcinoma.
  • For cataract surgery antisepsis, a 1% povidone-iodine solution has been used preoperatively. Eyedrops containing 0.8% povidone-iodine solution have been used three times every five minutes prior to surgery.
  • For chronic suppurative otitis media, three drops of 5% povidone-iodine eardrops have been used three times daily for 10 days, although other approaches, such as antibiotics, should be considered and discussed with a supervising healthcare professional.
  • For corpus vitreous degeneration, iodine eyedrops (3-4 times daily for 6-12 months) have been used.
  • For fibrocystic breast disease, approximately 1,500-6,000 micrograms of iodine has been taken by mouth daily for 6-18 months.
  • For 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. Other causes of goiter should also be considered under the supervision of a licensed healthcare professional. For endemic goiter, the following doses have been taken by mouth: 400 micrograms of iodine daily as di-iodotyrosine; 150 micrograms iodine or 500 micrograms of iodide with levothyroxine. For gestational goiter, under medical supervision, doses of 50-200 micrograms of iodide have been taken by mouth daily.
  • For hyperthyroidism, Graves' disease, thyroid storm, or as an adjunct to prescription drug inhibitors of thyroid function (such as propylthiouracil or methimazole), saturated solution of potassium iodide (SSKI, PIMA), 1-5 drops by mouth every eight hours, or Lugol solution (eight milligrams of iodide per drop), 2-6 drops (one milliliter) by mouth every eight hours, have been used. Lower doses may be used in pregnancy.
  • 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 two milliliters of iodized oil daily by mouth. In clinical trials, iodized salt was given to patients, with the levels of iodization ranging from 12 to 53 parts per million, for 4-60 months. 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®). For prolonged supplementation, a single annual intramuscular injection with one milliliter of Lipiodol® UF (480 milligrams of iodine) or 570 milligrams of oral iodine has been used.
  • As a mouthwash, 10-20 milliliters of povidone-iodine mouthwash has been used as a rinse. For prevention of plaque and gingivitis, mouth rinses have been used up to twice daily.
  • For mucositis prevention (from cancer treatment), povidone-iodine rinses have been used up to four times daily.
  • For oral intubation, gargling with 25 milliliters povidone-iodine has been used.
  • For pelvic infection, the addition of 20 milliliters of povidone-iodine gel at the vaginal apex after the usual vaginal preparation with povidone-iodine solution has been used before total abdominal hysterectomy.
  • For periodontitis or gingivitis, the concentration of povidone-iodine rinse has ranged from 0.1 to 10%, as an adjunct to scaling and root planing in patients with chronic periodontitis.
  • For pneumonia, 20 milliliters of a 10% povidone-iodine aqueous solution, reconstituted in a 60 milliliter solution with sterile water, has been used as a nasopharynx and oropharynx rinse.
  • As a preoperative before thyroidectomy, 5-10 drops of Lugol solution by mouth three times daily, or 2-6 drops twice or three times daily, given 10-21 days prior to surgery, have been used. Use for longer than 14 days can lead to "iodide escape" with rebound thyrotoxicosis and should be avoided. Potassium iodide (SSKI, PIMA), 1-2 drops 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.
  • For radiation emergencies, doses by mouth range from 16 to 130mg of potassium iodide tablets daily until the risk of significant radiation exposure ends.
  • For renal pelvic instillation sclerotherapy (RPIS), nine doses of povidone-iodine 0.2% at eight-hour intervals have been used.
  • For septicemia (serious bacterial infections in the blood), patients with gingivitis rinsed with 7.5% povidone-iodine for two minutes before ultrasonic scaling of the teeth.
  • For thyroid disease, potassium iodide (200 micrograms of iodide) by mouth 4-7 days after goiter resection was used, without benefit.
  • For thyrotoxicosis, parenteral treatment may be used, and one gram of sodium iodide by slow intravenous drip every 8-12 hours has been given. Management should be under the supervision of a licensed healthcare professional.
  • For upper airway sterilization, a 1% povidone-iodine solution inhaled via nebulizer, together with gargle, has been used twice daily.
  • For 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 to 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 antimicrobial effects to occur.

Children (younger than 18 years)

  • The daily Dietary Reference Intake recommended by the U.S. Institute of Medicine is 110-130 micrograms for infants up to 12 months old, 90 micrograms for children up to eight years old, and 120 micrograms for children up to 13 years old. The adequate intake (AI) for infants is 110 micrograms daily for ages 0-6 months and 130 micrograms daily for ages 7-12 months. The tolerable upper intake levels (UL) are 200 micrograms daily for ages 1-3 years, 300 micrograms daily for ages 4-8 years, 600 micrograms daily for ages 9-13 years; and 900 micrograms daily for ages 14-18 years (including pregnancy and lactation).
  • As an antimicrobial in the prevention of central venous catheter infection, a 10% povidone-iodine lotion daily or every 3-7 days has been used. Various concentrations of iodine are clinically used for skin and wound sterilization, for example, 2% tincture or 2% aqueous solution applied to affected areas.
  • For dental caries, following full mouth rehabilitation, children with early-childhood caries received 10% povidone-iodine topically for one year.
  • For goiter treatment, a single dose of 200 milligrams of Lipiodol® iodized oil (Guerbert, Roissy CdG Cedex, France) has been taken by mouth for up to one year.
  • 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 in children, including 150 micrograms by mouth daily.
  • For Kashin-Beck osteoarthropathy, iodized oil taken by mouth for 12 months was beneficial (information on the exact dose is lacking).
  • For ophthalmia neonatorum prevention, one drop of 2.5% povidone-iodine has been applied to the eye at birth.
  • For parenteral nutrition, the iodine supplementation of parenterally fed infants recommended by the European Society for Pediatric Gastroenterology, Hepatology, and Nutrition (ESPGHAN) is one microgram daily. However, some evidence suggests that this amount may be suboptimal. The recommended enteral intake of iodine for preterm infants is 30 micrograms per kilogram daily.
  • For radiation emergencies, potassium iodide (KI) should be taken by mouth just prior to, or as soon as possible after, exposure. For infants, babies, and children, KI is administered for exposure of five centigrays (cGy) or more. For birth through one month of age, 16 milligrams can be administered; for one month through three years of age, 32 milligrams can be administered; for 3-12 years of age, 65 milligrams can be administered; and for adolescents 12-18 years of age, 65 milligrams can be administered (or up to 120 milligrams if the adolescent is approaching adult size).

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 or hypersensitive to iodide or to organic preparations containing iodine. Hypersensitivity reactions may involve rash, angioedema (throat swelling), cutaneous or mucosal hemorrhage (bleeding), fever, arthralgias (joint pains), eosinophilia (abnormal blood counts), urticaria (hives), thrombotic thrombocytopenic purpura (blood disorder that causes blood clots), or severe periarteritis (inflammation around blood vessels). Reactions can be severe, and deaths have occurred with exposure.
  • Topical use of iodine preparations may irritate or burn tissues and cause sensitization in some individuals. Allergic reactions to povidone-iodine can be late in onset and, in vaginal surgeries, may present with atypical symptoms, such as acute urinary retention secondary to vulvar edema (swelling of the vagina).
  • This review does not comprehensively discuss the use of iodine-based intravenous contrast media for CT scan imaging, although life-threatening allergic reactions have been associated with their use. Individuals with known or suspected iodine hypersensitivity should inform their physicians prior to receiving contrast media.

Side Effects and Warnings

  • Adverse effects associated with intravenous iodine-based contrast agents used for CT scan imaging or radioactive iodine are not discussed in this review.
  • Iodine preparations used orally (by mouth) or topically (on the skin) are generally considered to be safe in healthy, nonallergic individuals when used in recommended amounts, not exceeding tolerated upper limits. Higher amounts taken acutely or chronically may result in adverse effects.
  • Acute iodine poisoning is rare and generally occurs only with doses of many grams. Symptoms may include burning of the mouth, throat, and stomach; fever; nausea; vomiting; diarrhea; cardiovascular compromise; and loss of consciousness or coma.
  • Chronic iodism, also known as iodide intoxication, may cause eye irritation, eyelid swelling, an unpleasant or metallic taste, burning or swelling of the mouth or throat, soreness of the gums or teeth, increased salivation, gastrointestinal upset, diarrhea, anorexia, flulike symptoms, sneezing, cough, pulmonary edema (fluid in the lungs), confusion, headache, fatigue, depression, numbness, tingling, pain, weakness, muscle aches, easy bruising, irregular heart beat, or acnelike skin lesions. Prolonged excess intake of iodide can lead to thyroid gland dysfunction, including hypo- or hyperthyroidism, parotiditis, thyroid gland hyperplasia (enlargement), thyroid adenoma (benign tumor), goiter, autoimmunity, and elevated thyroid-stimulating hormone (TSH) levels.
  • Iodine may leach out of iodized salt during washing or cooking. Therefore, it has been suggested to add iodized salt on cooked food rather than during cooking.
  • Individuals with autoimmune thyroid disease (AITD) may have increased sensitivity to the adverse effects of iodine. Those with previous iodine deficiency or nodular goiter may be particularly susceptible.
  • Use iodine products cautiously in patients with vitamin A or selenium deficiency, due to the risk of exacerbation of the effects of iodine deficiency and an altered response to iodine supplementation.
  • Topical cadexomer iodine has been associated with a local burning sensation in clinical trials. Cutaneous (skin) intolerance may develop with the topical use of iodinated polyvidone. Other reported reactions to tinctures include rash, blistering, crusting, irritation, itching, or erythema (reddening of the skin). Topical use of iodine may stain the skin.
  • Povidone-iodine bladder irrigation has been associated with increased risk of urinary tract infection.
  • It has been suggested that application of povidone-iodine to wounds (particularly surgical wounds) may locally suppress immune cells and wound healing and increase susceptibility to local infection.
  • Use cautiously in patients with depression or cardiovascular, dermatologic, or gastrointestinal disorders, due to the risk of side effects. Sodium iodide should be used cautiously in those with gastrointestinal obstruction.
  • Sodium iodide should be used cautiously in those with renal failure. Lugol solution and saturated solution of potassium iodide (SSKI, PIMA) should be avoided in those with hyperkalemia (high blood potassium levels).
  • Use cautiously in children with cystic fibrosis, which may be more sensitive to the adverse effects of excess iodine intake.
  • Iodine supplementation may initially lead to iodine-induced hyperthyroidism in iodine-deficient populations.
  • Use cautiously in patients with eosinophilia, which may be worsened in individuals that have iodine hypersensitivity.
  • Use cautiously in combination with amiodarone (Cordarone®), kelp, seaweed, and bladderwrack, which contain significant amounts of iodine. A kelp-containing tea has been reported to cause iodine-induced hypothyroidism.
  • Use cautiously in combination with antithyroid drugs and lithium salts, which may increase the risk of hypothyroid effects.
  • Use cautiously in combination with angiotensin-converting enzyme inhibitors, angiotensin receptor blockers, and potassium-sparing diuretics, due to a potential increased risk of hyperkalemia.
  • Use cautiously in patients with intestinal parasitic infestations treated with metronidazole, patients with iron deficiency, or in patients taking perchlorate, bugleweed (Lycopus virginicus, Lycopus europaeus), or goitrogens (present in high levels in cassava, cabbage, broccoli, cauliflower, and other cruciferous vegetables), due to the risk of reduced iodine uptake.
  • Use cautiously in combination with Lithospermum, which may lower thyroid hormone blood levels and interact with the effects of iodine on thyroid hormone levels.
  • Use cautiously in patients taking anticoagulant agents, as pharmacologic doses of potassium iodide may decrease effects of these agents.
  • Avoid skin contact with iodine crystals, as elemental iodine is an oxidizing irritant, and direct contact with skin may cause lesions.
  • Avoid iodine use in patients with dermatitis herpetiformis.
  • Avoid radiotherapy in iodine-deficient patients, as iodine-deficient individuals are more susceptible to radiation-induced thyroid cancer.
  • Internal administration of povidone may cause serious side effects that may even lead to kidney failure or death.
  • Lugol solution and saturated solution of potassium iodide (SSKI, PIMA) should be avoided in patients with pulmonary edema, bronchitis, or known tuberculosis.
  • Avoid with known allergy or hypersensitivity to iodide or to organic preparations containing iodine. Reactions can be severe, and deaths have occurred with exposure.
  • Avoid an air concentration of iodine greater than one milligram per cubic meter (eight-hour time-weighted average), as iodine vapor is irritating to eyes and respiratory tract.
  • Avoid excess iodine intake by pregnant women, due to the risk of excess iodine in the fetus or newborn, including thyroid dysfunction and skin irritation.
  • Avoid topical or vaginal iodine use for perianal preparation during prenatal diagnosis, lactation, delivery or postpartum antisepsis, due to possible iodine absorption by the newborn or absorption by the mother. Povidone-iodine use as an antiseptic agent during invasive procedures for prenatal diagnosis may lead to miscarriage.
  • Avoid consumption of high levels of seaweed products during lactation, due to the risk of hyper- or hypothyroidism in mothers and their nursing infants.

Pregnancy and Breastfeeding

  • Iodine requirements are increased during pregnancy. Iodine supplementation during pregnancy may be particularly relevant in areas of endemic iodine deficiency, such as nonindustrialized nations. Iodine deficiency during pregnancy has been associated with an increased incidence of miscarriage, stillbirth, birth defects, and mental retardation. Moreover, severe iodine deficiency during pregnancy may result in congenital hypothyroidism in the newborn. In contrast, excess iodine intake by pregnant women may lead to effects of excess iodine in the fetus or newborn, including thyroid dysfunction or skin irritation.
  • It has been suggested to avoid topical use of povidone-iodine for perianal preparation during delivery or postpartum antisepsis, due to possible iodine absorption by the newborn or absorption by the mother, leading to increased breast milk iodine concentrations. Other reports suggest that this may not be a significant concern. Povidone-iodine use as an antiseptic agent during invasive procedures for prenatal diagnosis may lead to miscarriage.
  • Iodine supplementation during breastfeeding may be particularly relevant in areas of endemic iodine deficiency, such as nonindustrialized nations. Infants are particularly vulnerable to the effects of iodine deficiency, and iodine deficient women may not be able to provide sufficient iodine in their breast milk.
  • Avoid consumption of high levels of seaweed products during lactation, due to the risk of hyper- or hypothyroidism in mothers and their nursing infants.
  • During the weaning period, infants not receiving iodine-containing complementary foods may be at risk of iodine deficiency, even in countries with iodized salt programs. The World Health Organization (WHO) recommends that mothers breastfeed through 24 months of age and that they feed children between the ages of 7 and 24 months foods fortified with iodine.

Interactions

Interactions with Drugs

  • Amiodarone (Cordarone®) contains significant amounts of iodine. Plasma iodine levels may be increased and additive with iodine supplements. Thyroid function should be monitored.
  • Concomitant use of angiotensin-converting enzyme inhibitors (ACE-Is) or angiotensin receptor blockers (ARBs) with potassium iodide increases the risk of hyperkalemia (high blood potassium levels). Examples of ACE inhibitors include benazepril (Lotensin®), captopril (Capoten®), enalapril (Vasotec®), fosinopril (Monopril®), lisinopril (Prinivil®, Zestril®), moexipril (Univasc®), perindopril (Aceon®), quinapril (Accupril®), ramipril (Altace®), and trandolapril (Mavik®). The ARBs include losartan (Cozaar®), valsartan (Diovan®), irbesartan (Avapro®), candesartan (Atacand®), telmisartan (Micardis®), and eprosartan (Teveten®).
  • The use of pharmacologic doses of potassium iodide may decrease the anticoagulant effect of warfarin (Coumadin®).
  • Children with intestinal parasitic infestations treated with metronidazole have experienced reduced efficacy of oral supplementation with iodized ethyl esters by interfering with its absorption.
  • Perchlorate inhibits the uptake of iodide into the thyroid gland.
  • Additive hypothyroid effects may occur with the use of iodine products in combination with antithyroid drugs (methimazole, propylthiouracil).
  • Additive hypothyroid effects may occur with the use of iodine products such as potassium iodide in combination with lithium salts. Lugol solution can increase lithium toxicity by inducing additive hypothyroid effects.
  • Concomitant use of potassium iodide with potassium-sparing diuretics may increase the risk of hyperkalemia. Examples of potassium-sparing diuretics include spironolactone (Aldactone®), triamterene (Dyrenium®), and amiloride (Midamor®).
  • Iodine may also interact with antibiotics, anticancer agents, cardiovascular agents, neurologic agents, or thyroid hormones.

Interactions with Herbs and Dietary Supplements

  • Bugleweed (Lycopus virginicus, Lycopus europaeus) may reduce iodine uptake.
  • High iodine content can be found in kelp, seaweed, or bladderwrack and may add to the effects of iodine supplementation.
  • Ingestion of Lithospermum may lower thyroid hormone blood levels and may interact with the effects of iodine on thyroid hormone levels.
  • Selenium deficiency may exacerbate the effects of iodine deficiency.
  • Goitrogens, present in high levels in cassava, cabbage, broccoli, cauliflower, and other cruciferous vegetables, may interfere with the uptake of iodine in the thyroid.
  • The use of pharmacologic doses of potassium iodide may decrease the anticoagulant effects of herbs and supplements with blood-thinning effects.
  • Iodine may also interact with antiarrhythmics, antibacterials, anticancer herbs and supplements, cardiovascular herbs and supplements, herbs and supplements that affect the thyroid, herbs and supplements with angiotensin-converting enzyme-inhibiting effects, herbs and supplements with diuretic effects, iron, neurologic herbs and supplements, potassium, vitamin A, and zinc.

Attribution
  • This information is based on a systematic review of scientific literature edited and peer-reviewed by contributors to the Natural Standard Research Collaboration (www.naturalstandard.com).

Bibliography
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  2. Bürgi H. Iodine excess. Best Pract Res Clin Endocrinol Metab. 2010 Feb;24(1):107-15.
  3. Durani P, Leaper D. Povidone-iodine: use in hand disinfection, skin preparation and antiseptic irrigation. Int Wound J. 2008 Jun;5(3):376-87.
  4. Fournel I, Tiv M, Soulias M, et al. Meta-analysis of intraoperative povidone-iodine application to prevent surgical-site infection. Br J Surg. 2010 Nov;97(11):1603-13.
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  7. Patrick L. Iodine: deficiency and therapeutic considerations. Altern Med Rev. 2008 Jun;13(2):116-27.
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  9. Sahrmann P, Puhan MA, Attin T, et al. Systematic review on the effect of rinsing with povidone-iodine during nonsurgical periodontal therapy. J Periodontal Res. 2010 Apr;45(2):153-64.
  10. Schomburg L, Köhrle J. On the importance of selenium and iodine metabolism for thyroid hormone biosynthesis and human health. Mol Nutr Food Res. 2008 Nov;52(11):1235-46.
  11. Szybinski Z, Jarosz M, Hubalewska-Dydejczyk A, et al. Iodine-deficiency prophylaxis and the restriction of salt consumption - a 21st century challenge. Endokrynol Pol. 2010 Jan-Feb;61(1):135-40.
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Copyright © 2011 Natural Standard (www.naturalstandard.com)


The information in this monograph is intended for informational purposes only, and is meant to help users better understand health concerns. Information is based on review of scientific research data, historical practice patterns, and clinical experience. This information should not be interpreted as specific medical advice. Users should consult with a qualified healthcare provider for specific questions regarding therapies, diagnosis and/or health conditions, prior to making therapeutic decisions.


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