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Potassium Iodide and Iodine

Generic name: iodine/potassium iodide systemic

Brand names: Lugol's, Xymodine

Dosage Forms

Excipient information presented when available (limited, particularly for generics); consult specific product labeling.

Solution, External:

Generic: Potassium iodide 10% and iodine 5% (8 mL)

Solution, Oral:

Generic: Potassium iodide 10% and iodine 5% (14 mL, 473 mL)

Tincture, External:

Generic: Potassium iodide 5% and iodine 7% (30 mL, 480 mL)


Mechanism of Action

In hyperthyroidism, iodine temporarily inhibits thyroid hormone synthesis and secretion into the circulation; use also decreases thyroid gland size and vascularity. Serum T4 and T3 concentrations can be reduced for several weeks with use but effect will not be maintained.

Following radioactive iodine exposure, potassium iodide blocks uptake of radioiodine by the thyroid, reducing the risk of thyroid cancer.


Onset of Action

Hyperthyroidism: 24 to 48 hours; Peak effect: 10 to 15 days after continuous therapy

Use: Labeled Indications

Antiseptic: Topical antiseptic

Thyroidectomy preparation: Treatment of hyperthyroidism in the immediate preoperative period in patients undergoing thyroidectomy.

Note: Iodine therapy is not recommended in the preoperative setting in patients with thyrotoxicosis caused by a toxic adenoma or toxic multinodular goiter due to the risk of exacerbating hyperthyroidism (Ross 2016).

Thyroid storm: Treatment of thyroid storm (as part of a multimodality treatment approach).

Note: The American Thyroid Association and American Association of Clinical Endocrinologists guidelines for the management of hyperthyroidism and other causes of thyrotoxicosis recommend potassium iodide and iodine (Lugol's solution) as an acceptable alternative to saturated solution of potassium iodide (SSKI) in the management of adults with thyrotoxic crisis/thyroid storm (Ross 2016).

Use: Off Label

Thyroid gland protection during radiopharmaceutical useyes

Based on the European Association of Nuclear Medicine (EANM) procedure guidelines for 131 I-meta-iodobenzylguanidine (131 I-mIBG) therapy, potassium iodide and iodine is effective and recommended for thyroid gland protection during radiopharmaceutical use.


Hypersensitivity to iodine or any component of the formulation; active tuberculosis; dermatitis herpetiformis; hypocomplementemic vasculitis; nodular thyroid disease with heart disease

Dosage and Administration

Dosing: Adult

Note: Lugol's 5% solution (potassium iodide 10% and iodine 5%) contains ~6.25 mg iodine/iodide per drop (ACR-SPR 2015).

Antiseptic: Topical: Apply directly to area(s) requiring antiseptic.

Thyroidectomy preparation in patients with Graves disease: Lugol's 5% solution: Oral: 5 to 7 drops (0.25 to 0.35 mL) 3 times daily; administer for 10 days before surgery; if not euthyroid prior to surgery, consider concurrent beta-blockade (eg, propranolol) in the immediate preoperative period to reduce the risk of thyroid storm (Ross 2016)

Thyroid gland protection during radiopharmaceutical use (off-label use): Lugol's 5% solution: Oral: Regimens/protocols vary by radiopharmaceutical. Generally, ~100 mg/day of iodine/iodide is required for thyroid block (ACR-ACNM [Subramaniam 2017]; Anderson 2012; Taïeb 2012). This dose can be achieved with ~16 drops/day of Lugol's 5% solution (eg, 16 drops x 6.25 mg iodine/iodide per drop = 100 mg iodine/iodide). The following product-specific recommendations are provided in the manufacturer's labeling:

Iodine I-123 radiopharmaceuticals: 100 mg/day of iodine/iodide (manufacturer's labeling [Adreview, Datscan]).

Iodine I-125 and I-131 radiopharmaceuticals: 10 drops 3 times daily (manufacturer's labeling [Jeanatope, Megatope, Volumex]). The manufacturer's labeling for Azedra does not provide specific dosing recommendations.

Note: Initiate 1 to 48 hours prior to radiopharmaceutical exposure and continue after radiopharmaceutical administration until risk of exposure has diminished (treatment initiation time and duration are dependent on the radiopharmaceutical agent used, consult specific protocol or labeling.

Thyrotoxic crisis/thyroid storm: Lugol's 5% solution: Oral: 4 to 8 drops every 6 to 8 hours; initiate therapy at least 1 hour following the initial dose of antithyroid drug therapy (eg, propylthiouracil, methimazole) (Nayak 2006; Ross 2016)

Dosing: Geriatric

Refer to adult dosing.

Dosing: Pediatric

Note: Dosing is listed in terms of drops/dose; check instructions carefully before dispensing or administering.

Thyrotoxic crisis/thyroid storm: Limited data available: Children and Adolescents: Lugol's solution: Oral: 4 to 10 drops 3 times daily; begin therapy preferably 2 hours following the initial dose of either propylthiouracil or methimazole (Fuhrman 2011; Nichols 2008)


Topical: Apply topically directly to area(s) requiring antiseptic.

Oral: Dilute with water or juice.


Store at room temperature of 15°C to 30°C (59°F to 86°F). Protect from light and keep container tightly closed.

Drug Interactions

Aliskiren: Potassium Salts may enhance the hyperkalemic effect of Aliskiren. Monitor therapy

Angiotensin II Receptor Blockers: Potassium Salts may enhance the hyperkalemic effect of Angiotensin II Receptor Blockers. Monitor therapy

Angiotensin-Converting Enzyme Inhibitors: Potassium Salts may enhance the hyperkalemic effect of Angiotensin-Converting Enzyme Inhibitors. Monitor therapy

Cardiac Glycosides: Antithyroid Agents may increase the serum concentration of Cardiac Glycosides. Monitor therapy

Drospirenone: Potassium Salts may enhance the hyperkalemic effect of Drospirenone. Monitor therapy

Eplerenone: May enhance the hyperkalemic effect of Potassium Salts. Management: This combination is contraindicated in patients receiving eplerenone for treatment of hypertension. Consider therapy modification

Heparin: May enhance the hyperkalemic effect of Potassium Salts. Monitor therapy

Heparins (Low Molecular Weight): May enhance the hyperkalemic effect of Potassium Salts. Monitor therapy

Lithium: Potassium Iodide may enhance the hypothyroid effect of Lithium. Monitor therapy

Nicorandil: May enhance the hyperkalemic effect of Potassium Salts. Monitor therapy

Potassium-Sparing Diuretics: Potassium Salts may enhance the hyperkalemic effect of Potassium-Sparing Diuretics. Consider therapy modification

Sodium Iodide I131: Antithyroid Agents may diminish the therapeutic effect of Sodium Iodide I131. Management: Discontinue antithyroid therapy 3-4 days prior to sodium iodide I-131 administration. Avoid combination

Theophylline Derivatives: Antithyroid Agents may increase the serum concentration of Theophylline Derivatives. Exceptions: Dyphylline. Monitor therapy

Vitamin K Antagonists (eg, warfarin): Antithyroid Agents may diminish the anticoagulant effect of Vitamin K Antagonists. Consider therapy modification

Test Interactions

Iodide may alter thyroid function tests.

Adverse Reactions

Frequency not defined.

Cardiovascular: Cardiac arrhythmia, myxedema

Central nervous system: Confusion, fatigue, metallic taste, numbness, tingling sensation

Dermatologic: Skin rash

Endocrine & metabolic: Goiter, hyperthyroidism, hypothyroidism

Gastrointestinal: Diarrhea, enlargement of salivary glands, gastric distress, gastrointestinal hemorrhage, nausea, salivary gland disease (tenderness), stomach pain, vomiting

Hematologic & oncologic: Adenopathy, thyroid adenoma

Hypersensitivity: Hypersensitivity reaction (angioedema, cutaneous and mucosal hemorrhage, serum sickness-like symptoms)

Neuromuscular & skeletal: Arthralgia, weakness

Respiratory: Pharyngeal edema

Miscellaneous: Drug overdose (with prolonged treatment/high doses), fever, iodism


Concerns related to adverse effects:

  • Hypothyroidism: Prolonged use can lead to hypothyroidism.
  • Skin reactions: Can cause acne flare-ups and/or dermatitis.

Disease-related concerns:

  • Adrenal insufficiency: Use with caution in patients with Addison's disease.
  • Bronchitis: Use with caution in patients with acute bronchitis.
  • Cardiac disease: Use with caution in patients with cardiac disease.
  • Myotonia congenita: Use with caution in patients with myotonia congenita.
  • Renal impairment: Use with caution in patients with renal impairment.
  • Thyroid disease: Use with caution in patients with a history of hyperthyroidism; use is contraindicated in nodular thyroid conditions with heart disease.
  • Tuberculosis: Use with caution in patients with tuberculosis.

Concurrent drug therapy issues:

  • Drug-drug interactions: Potentially significant interactions may exist, requiring dose or frequency adjustment, additional monitoring, and/or selection of alternative therapy. Consult drug interactions database for more detailed information.

Monitoring Parameters

Thyroid function tests, signs/symptoms of hyperthyroidism; following radioiodine exposure, thyroid function should be monitored in pregnant women, neonates, and young infants if repeat doses are required.


Pregnancy Risk Factor

D (potassium iodide)

Pregnancy Considerations

Iodide crosses the placenta (may cause hypothyroidism and goiter in fetus/newborn). Use for protection against thyroid cancer secondary to radioactive iodine exposure is considered acceptable based upon risk:benefit, keeping in mind the dose and duration. Repeat dosing should be avoided if possible. Refer to Iodine for additional information.

Patient Education

  • Discuss specific use of drug and side effects with patient as it relates to treatment. (HCAHPS: During this hospital stay, were you given any medicine that you had not taken before? Before giving you any new medicine, how often did hospital staff tell you what the medicine was for? How often did hospital staff describe possible side effects in a way you could understand?)
  • Have patient report immediately to prescriber severe abdominal pain, severe nausea, vomiting, or diarrhea (HCAHPS).
  • Educate patient about signs of a significant reaction (eg, wheezing; chest tightness; fever; itching; bad cough; blue skin color; seizures; or swelling of face, lips, tongue, or throat). Note: This is not a comprehensive list of all side effects. Patient should consult prescriber for additional questions.

Intended Use and Disclaimer: Should not be printed and given to patients. This information is intended to serve as a concise initial reference for health care professionals to use when discussing medications with a patient. You must ultimately rely on your own discretion, experience, and judgment in diagnosing, treating, and advising patients.

Source: Wolters Kluwer Health. Last updated June 5, 2019.