Potassium Iodide (Monograph)

Brand names: Iosat, SSKI, ThyroSafe, ThyroShield
Drug class: Antithyroid Agents
ATC class: R05CA02
VA class: RE302
CAS number: 7681-11-0

Medically reviewed by Drugs.com on May 19, 2023. Written by ASHP.

Introduction

Antithyroid agent,¹⁶² antisporotrichotic agent,¹⁶² and expectorant.^{137 162}

Uses for Potassium Iodide

Hyperthyroidism

Preoperative management of hyperthyroidism in patients with Graves’ disease undergoing thyroidectomy^{† [off-label]}.^{151 152 154 160 161 162 165 171} American Thyroid Association (ATA), American Association of Clinical Endocrinologists (AACE), and others recommend that patients with Graves’ disease scheduled for surgery be rendered euthyroid using other antithyroid agents (preferably methimazole) and then receive potassium iodide for 7–14 days (usually 10 days) in immediate preoperative period.^{152 160 161 165} In exceptional circumstances when euthyroid state cannot be achieved prior to thyroidectomy (e.g., urgent need for surgery, allergy to antithyroid drugs), these experts recommend use of potassium iodide and a β-adrenergic blocking agent (e.g., propranolol) in immediate preoperative period.¹⁶⁰ Preoperative potassium iodide has traditionally been used in such patients to decrease thyroid blood flow, vascularity, and intraoperative blood loss;^{151 160 162 165 171} however, some clinicians question necessity and benefits of this strategy.^{161 182 183}

Management of severe, life-threatening thyrotoxicosis^{† [off-label]} (thyroid storm, thyrotoxicosis crisis) in conjunction with other antithyroid agents (e.g., methimazole, propylthiouracil), β-adrenergic blocking agents (e.g., propranolol), corticosteroids (hydrocortisone, dexamethasone), treatment of hyperpyrexia, and appropriate fluid, electrolyte, and respiratory support.^{154 160 161 162 165} Initiate other antithyroid agents first to block thyroid hormone synthesis and conversion of tetraiodothyronine (thyroxine, T₄) to triiodothyronine (T₃); initiate potassium iodide 1 hour after the other agents to block new hormone synthesis and thyroid hormone release.¹⁶⁰

Radiation Emergency

Blockage of thyroidal uptake of radioactive isotopes of iodine (e.g., I 131) that may be released into the environment (e.g., from a nuclear power plant) to minimize the risk of radiation-induced thyroid neoplasms related to internal exposures to radioiodines (inhaled or ingested).^{100 101 105 138 139 141 144 145 149 150 153 155 156 164 166 167 174} Has no impact on uptake of other radioactive materials and does not provide protection against external irradiation of any kind.¹³⁸

Used as an adjunct to other protective measures (e.g., evacuation, sheltering, assurance of uncontaminated milk and food).^{138 139 145 150 153 155 162 164 167} Individuals unable to tolerate potassium iodide and individuals for whom repeat doses of the drug are a concern (e.g., neonates ≤1 month of age, pregnant or lactating women) should be given priority with regard to these other protective measures.¹³⁸

For use in radiation emergencies, potassium iodide is commercially available in appropriate dosage forms (see Dosage and Administration)^{150 153 155 164} and may also be retained in state or local stockpiles.^{139 145 167}

Decisions to recommend protective measures (including use of potassium iodide) in an emergency situation related to a US nuclear power plant reside with state and/or local government authorities responsible for radiological emergency planning and response.^{101 138 139 145 150 153 155 164 166 167} (See Advice to Patients.)

Exposure to Radiopharmaceuticals

Used to protect thyroid during diagnostic or therapeutic use of radiopharmaceuticals or drugs that have radioactive components^{† [off-label]} (e.g., iodine I 131 tositumomab; no longer commercially available in US).^{162 180 181}

Initiated prior to administration of radiolabeled diagnostic or therapeutic agent to saturate thyroid and protect it from uptake of radioiodide; continued until estimated activity of radiolabeled agent has decreased to acceptable levels after completion of the procedure or treatment.^{162 180 181}

Sporotrichosis

Treatment of cutaneous sporotrichosis^{† [off-label]} (localized to skin; also known as fixed cutaneous sporotrichosis) and lymphocutaneous sporotrichosis^{† [off-label]} (involves skin, subcutaneous tissues, regional lymphatics) caused by Sporothrix schenckii.^{108 112 118 120 121 124 143 146 168 169 172 177 178}

Because it is inexpensive and generally effective,^{124 143 146 172 177 178} potassium iodide (oral solution containing 1 g/mL; also known as saturated solution of potassium iodide [SSKI]) has historically been a standard of care for treatment of cutaneous and lymphocutaneous sporotrichosis and is a drug of first choice for these infections in some resource-limited settings and countries where the disease is endemic.^{143 146 169 172 176} However, safety and efficacy for treatment of these infections not established in controlled clinical trials.¹⁷⁶

IDSA and others recommend itraconazole as drug of choice for treatment of cutaneous and lymphocutaneous sporotrichosis; terbinafine and potassium iodide (oral solution containing 1 g/mL; also known as saturated solution of potassium iodide [SSKI]) are preferred alternatives.^{168 169} Local hyperthermia (i.e., direct application of heat using pocket warmer, infrared or far-infrared heater, or similar device that warms tissue to 42–43°C) is another alternative for treatment of cutaneous sporotrichosis when antifungals or potassium iodide cannot be used (e.g., pregnant or nursing women).¹⁶⁹

Not effective and should not be used for treatment of extracutaneous sporotrichosis^† (pulmonary, osteoarticular, meningeal) or disseminated sporotrichosis^†; IV amphotericin B and oral itraconazole are drugs of choice for these forms of sporotrichosis.^{124 168 169}

Cough

Potassium iodide (oral solution containing 1 g/mL; also known as saturated solution of potassium iodide [SSKI]) has been used as an expectorant in the symptomatic management of chronic pulmonary diseases where tenacious mucus complicates the condition (e.g., bronchial asthma, bronchitis, pulmonary emphysema).¹³⁷ However, efficacy not established and the drug generally has been replaced by more effective and safer expectorants.^a

Related/similar drugs

benzonatate, diphenhydramine, Benadryl, guaifenesin, dextromethorphan, Mucinex, methimazole

Potassium Iodide Dosage and Administration

Administration

Oral Administration

Administer orally.^{137 150 153 154 155 164}

Oral solution containing 65 mg/mL: Administer undiluted using calibrated dropper provided by manufacturer.¹⁵⁵

Oral solution containing 1 g/mL (also known as saturated solution of potassium iodide [SSKI]): Dilute dose in glassful of water, fruit juice, or milk.¹³⁷ To minimize GI irritation, take dose with food or milk.¹³⁷ Manufacturer provides calibrated dropper marked to deliver 300 mg (0.3 mL) or 600 mg (0.6 mL).¹³⁷ If administered using standard medicinal dropper, each drop (0.05 mL) contains 50 mg of potassium iodide.^{160 163}

Strong iodine oral solution containing 50 mg of iodine and 100 mg of potassium iodide per mL (also known as Lugol’s solution; commercially available but not FDA approved): Dilute dose in water or juice.¹⁵⁴ If administered using standard medicinal dropper, each drop contains 8 mg of iodide.¹⁶⁰

Extemporaneous Oral Solutions

For use during a radiation emergency in infants, small children, and others who cannot swallow tablets, oral solution (liquid mixture) containing 8.125 mg/5 mL (8.125 mg/teaspoon) or 16.25 mg/5 mL (16.25 mg/teaspoon) can be prepared extemporaneously using 65- or 130-mg tablets.^{140 150 164}

Extemporaneous oral solution containing 8.125 mg/5 mL (8.125 mg/teaspoon): Manufacturers state pulverize 65-mg tablet in small bowl using the back of a teaspoon; add 4 teaspoons (20 mL) of water and mix until dissolved; add this mixture to 4 teaspoons (20 mL) of milk (low-fat white or chocolate), orange juice, flat soda, raspberry syrup, or infant formula.^{150 164}

Extemporaneous oral solution containing 16.25 mg/5 mL (16.25 mg/teaspoon): Manufacturers state pulverize 130-mg tablet in small bowl using the back of a teaspoon; add 4 teaspoons (20 mL) of water and mix until dissolved; add this mixture to 4 teaspoons (20 mL) of milk (low-fat white or chocolate), orange juice, flat soda, raspberry syrup, or infant formula.¹⁵³

Alternatively, to prepare oral solution containing 16.25 mg/5 mL (16.25 mg/teaspoon), FDA states place two 65-mg tablets or one 130-mg tablet in small bowl; add 4 teaspoons (20 mL) of water and allow to soak for 1 minute; using the back of the teaspoon, crush tablet(s) in the water until there are no large pieces; add this mixture to 4 teaspoons (20 mL) of milk (white or chocolate), orange juice, soda (e.g., cola), infant formula, raspberry syrup, or water.¹⁴⁰

Store extemporaneous oral solutions in a refrigerator for up to 7 days.^{140 150 153 164}

Dosage

Pediatric Patients

Hyperthyroidism†

Preoperative Use in Patients with Graves’ Disease Undergoing Thyroidectomy†

Oral

Oral solution containing 1 g/mL (also known as saturated solution of potassium iodide [SSKI]): 150–350 mg (3–7 drops or 0.15–0.35 mL) 3 times daily for 10 days in immediate preoperative period.¹⁶⁰

Ideally, administer only after patient is euthyroid after treatment with other antithyroid agents.¹⁶⁰ (See Hyperthyroidism under Uses.)

Thyroid Storm (Thyrotoxicosis Crisis)†

Oral

Oral solution containing 1 g/mL (also known as saturated solution of potassium iodide [SSKI]): 50–250 mg (1–5 drops or 0.05–0.25 mL) 3 times daily suggested by some clinicians.¹⁶³

Radiation Emergency

Oral

Recommended dosage and duration to provide protection during radiation emergency (inhalation or ingestion exposure) is based on predicted thyroid exposure, age, and weight (see Table 1 and Table 2).^{138 150 153 155 156 164}

For optimal protection, take before or immediately coincident with passage of a radioactive cloud or within 1–2 hours of exposure; administration 3–4 hours after exposure may still provide substantial protection.^{138 174}

Use for self-medication only when directed by public authorities.^{138 150 153 155 156 164 166} FDA recommends potassium iodide in infants, children, and adolescents when predicted thyroid exposure is ≥5 centigrays (cGy).¹³⁸

Single daily dose; do not take more often than once every 24 hours.^{138 150 153 155 156 164 166} Continue daily dose as directed by public authorities until risk of substantial exposure to radioiodines by inhalation or ingestion no longer exists.^{138 150 153 155 156 164 166}

Neonates ≤1 month of age: Avoid repeat administration.^{138 150 153 155 156 164 166} Consult clinician if more than a single dose indicated.^{138 150 153 155 164 166} (See Pediatric Use under Cautions.)

Sporotrichosis†

Cutaneous or Lymphocutaneous Sporotrichosis†

Oral

Oral solution containing 1 g/mL (also known as saturated solution of potassium iodide [SSKI]): Initially, 50 mg (1 drop or 0.05 mL) 3 times daily.^{169 172} Gradually increase dosage as tolerated to maximum of 1 drop/kg 3 times daily or 2–2.5 g (40–50 drops or 2–2.5 mL) 3 times daily, whichever is lowest.¹⁶⁹

Usual treatment duration is 3–6 months.^{124 172} IDSA recommends continuing treatment for 2–4 weeks after cutaneous lesions resolve;¹⁶⁹ others recommend continuing for 4–6 weeks after cutaneous lesions resolve.¹⁶³

Adults

Hyperthyroidism†

Preoperative Use in Patients with Graves’ Disease Undergoing Thyroidectomy†

Oral

Oral solution containing 1 g/mL (also known as saturated solution of potassium iodide [SSKI]): 50–100 mg (1–2 drops or 0.05–0.1 mL) 3 times daily for 10 days in immediate preoperative period.¹⁶⁰

Strong iodine solution (also known as Lugol’s solution; commercially available but not FDA approved): 5–7 drops or 0.25–0.35 mL 3 times daily for 10 days in immediate preoperative period.¹⁶⁰

Ideally, administer only after patient is euthyroid after treatment with other antithyroid agents.¹⁶⁰ (See Hyperthyroidism under Uses.)

Thyroid Storm (Thyrotoxicosis Crisis)†

Oral

Oral solution containing 1 g/mL (also known as saturated solution of potassium iodide [SSKI]): 250 mg (5 drops or 0.25 mL) every 6 hours.¹⁶⁰

Initiate 1 hour after initial dose of other antithyroid agents.¹⁶⁰ (See Hyperthyroidism under Uses).

Radiation Emergency

Oral

Recommended dosage and duration to provide protection during radiation emergency (inhalation or ingestion exposure) is based on predicted thyroid exposure, age, and pregnancy or lactation status.^{138 150 153 155 156 164}

For optimal protection, take before or immediately coincident with passage of a radioactive cloud or within 1–2 hours of exposure; administration 3–4 hours after exposure may still provide substantial protection.^{138 174}

Use for self-medication only when directed by public authorities.^{138 150 153 155 156 164 166} FDA recommends potassium iodide in adults 19 through 40 years of age when predicted thyroid exposure is ≥10 cGy and in pregnant or lactating women when predicted thyroid exposure is ≥5 cGy;¹³⁸ because of risk of hypothyroidism, recommended in adults >40 years of age only when predicted thyroid exposure is ≥500 cGy.¹³⁸

Single daily dose; do not take more often than once every 24 hours.^{138 150 153 155 156 164 166} Continue daily dose as directed by public authorities until risk of substantial exposure to radioiodines by inhalation or ingestion no longer exists.^{138 150 153 155 156 164 166}

Tablets: 130 mg once daily (one 130-mg tablet or two 65- mg tablets once daily).^{138 150 153 156 164}

Oral solution containing 65 mg/mL: 130 mg once daily (2 mL once daily).¹⁵⁵

Extemporaneous oral solution containing 16.25 mg/5 mL (16.25 mg/teaspoon): 130 mg once daily (40 mL or 8 teaspoons once daily).¹⁴⁰

Pregnant and lactating women: Avoid repeat administration.^{138 150 153 155 156 164 166} Consult clinician if more than a single dose indicated.^{138 150 153 155 164} (See Pregnancy and See Lactation under Cautions.)

Sporotrichosis†

Cutaneous or Lymphocutaneous Sporotrichosis†

Oral

Oral solution containing 1 g/mL (also known as saturated solution of potassium iodide [SSKI]): Initially, 250 mg (5 drops or 0.25 mL) 3 times daily.¹⁶⁹ Gradually increase dosage as tolerated to a maximum of 2–2.5 g (40–50 drops or 2–2.5 mL) 3 times daily.^{124 169}

Usual treatment duration is 3–6 months.^{124 172} IDSA recommends continuing treatment for 2–4 weeks after cutaneous lesions resolve;¹⁶⁹ others recommend continuing for 4–6 weeks after cutaneous lesions resolve.¹⁶³

Cough

Oral

Oral solution containing 1 g/mL (also known as saturated solution of potassium iodide [SSKI]): 300 or 600 mg (0.3 or 0.6 mL) 3 or 4 times daily.¹³⁷

Prescribing Limits

Pediatric Patients

Radiation Emergency

Oral

Neonates ≤1 month of age: Maximum 1 dose without consulting clinician.¹³⁸ (See Pediatric Use under Cautions.)

Pediatric patients >1 month through 18 years of age: Maximum 1 dose every 24 hours.^{137 153 155 164}

Sporotrichosis†

Cutaneous or Lymphocutaneous Sporotrichosis†

Oral

Oral solution containing 1 g/mL (also known as saturated solution of potassium iodide [SSKI]): Maximum 1 drop/kg or 2–2.5 g (40–50 drops or 2–2.5 mL) 3 times daily, whichever is lowest.¹⁶⁹

Adults

Radiation Emergency

Oral

Pregnant and lactating women: Maximum 1 dose without consulting clinician.¹³⁸ (See Pregnancy and See Lactation under Cautions.)

Other adults ≥19 years of age: Maximum 1 dose every 24 hours.^{138 140}

Sporotrichosis†

Cutaneous or Lymphocutaneous Sporotrichosis†

Oral

Oral solution containing 1 g/mL (also known as saturated solution of potassium iodide [SSKI]): Maximum 2–2.5 g (40–50 drops or 2–2.5 mL) 3 times daily.^{124 169}

Cautions for Potassium Iodide

Contraindications

• Known sensitivity to iodides or any ingredient in the formulation.^{137 150 153 154 155 164}

• Dermatitis herpetiformis.^{150 153 155 164}

• Hypocomplementemic vasculitis.^{150 153 155 164}

• Nodular thyroid disease (e.g., multinodular goiter) with heart disease.^{150 153 155 164}

Warnings/Precautions

Warnings

Fetal/Neonatal Morbidity

May cause fetal harm (i.e., abnormal thyroid function, fetal goiter).^{137 157 160 162} (See Pregnancy under Cautions.)

Sensitivity Reactions

Hypersensitivity Reactions

Angioedema, cutaneous and mucosal hemorrhage, and signs and symptoms resembling serum sickness (e.g., fever, arthralgia, lymph node enlargement, eosinophilia) may occur.^{137 162} Urticaria, thrombotic thrombocytopenic purpura, and fatal periarteritis also reported.^a

Patients with hypocomplementemic vasculitis associated with chronic urticaria or systemic lupus erythematosus are at increased risk of adverse effects and severe systemic illness;^{150 153 155 164 a} do not use in such patients.^{150 153 155 164} (See Contraindications under Cautions.)

Patients with dermatitis herpetiformis are at increased risk of adverse effects;^{150 153 155 164} do not use in such patients.^{150 153 155 164} (See Contraindications under Cautions.)

If hypersensitivity reaction occurs (e.g., difficulty breathing/speaking/swallowing, shortness of breath, wheezing, swelling of mouth/tongue/throat/face/hands/feet, rash), discontinue the drug.^{150 153 155 164}

Major Toxicities

Iodism (Chronic Iodine Poisoning)

Iodism (chronic iodine poisoning) may occur with long-term therapy or high dosage.^{137 154 162} Manifestations include burning in mouth or throat, severe headache, metallic taste, soreness of teeth and gums, head cold symptoms, coryza, sneezing, eye irritation with eyelid swelling, unusual increase in salivation, acneiform lesions in seborrheic areas, and, rarely, severe skin eruptions (ioderma).^{137 152 162 170} Productive cough, pulmonary edema, dyspnea, bronchospasm, and swelling/tenderness of parotid and submaxillary glands, throat inflammation, gastric irritation, and diarrhea (sometimes bloody) also may occur.¹⁶²

If manifestations of iodism occur, discontinue potassium iodide and initiate appropriate supportive therapy.¹³⁷ Symptoms usually resolve soon after drug discontinued;¹³⁷ abundant fluid and salt intake may help eliminate iodide.¹³⁷

General Precautions

Alterations in Thyroid Function

Long-term use or high dosage may induce hyperthyroidism, particularly in older individuals, patients with preexisting nontoxic nodular goiter, and patients residing in areas with endemic iodine deficiency.^{138 162} Symptoms of hyperthyroidism may include irregular heartbeat and chest pain.^{150 153 155 164}

In some patients, long-term use may result in goiter and severe hypothyroidism.^{137 138 151 152 162}

Use with caution in patients with preexisting thyroid disease (multinodular goiter, Graves’ disease, autoimmune thyroiditis), especially if therapy is expected to last longer than a few days.^{137 138 156}

Patients who have nodular thyroid disease (e.g., multinodular goiter) with heart disease are at increased risk of adverse effects;^{150 153 155 164} do not use in such patients.^{150 153 155 164} (See Contraindications under Cautions.)

Concomitant Illnesses

Use with caution in patients with Addison’s disease,¹³⁷ cardiac disease,^{137 163} myotonia congenita,¹³⁷ active tuberculosis,¹³⁷ acute bronchitis,¹³⁷ or renal impairment.^{137 163}

Use during Radiation Emergency

Use with caution and as directed by public authorities.^{138 150 153 155 156 164 166}

For radiation emergency, may be used in patients with preexisting thyroid disease who do not have nodular thyroid conditions with heart disease; however, consult clinician if potassium iodide therapy expected to last longer than a few days.^{150 153 155 164}

Eye or Skin Exposure

Vesication and desquamation may occur if strong iodine solution (also known as Lugol’s solution; commercially available but not FDA approved) is allowed to pool in contact with skin.¹⁵⁴

If accidental contact with skin or eyes occurs, flush with copious amounts of water for 15 minutes.¹⁵⁴

Specific Populations

Pregnancy

Category D.^{137 157}

Iodides readily cross the placenta;^{137 138 157 162} abnormal thyroid function (hypothyroidism) and/or goiter may occur in the neonate.^{137 149 157 160 162} Fetal thyroid may be most susceptible to effects of excess iodine at end of gestation.¹⁶⁰

Some experts state potassium iodide is contraindicated in pregnant women.¹⁶³ AAP states use of potassium iodide as an expectorant is contraindicated during pregnancy.¹⁵⁷

No evidence that short-term use (e.g., 10 days) of potassium iodide for preoperative management of hyperthyroidism in pregnant women with Graves’ disease undergoing thyroidectomy^† is harmful to the fetus.^{157 160} If thyroidectomy necessary for treatment of hyperthyroidism during pregnancy, ATA and AACE recommend the surgery be performed during second trimester.¹⁶⁰

In radiation emergency, FDA recommends that pregnant women receive potassium iodide for their own protection and that of the fetus.¹³⁸ However, because of risks of excess iodine to fetal thyroid function, avoid repeat administration during pregnancy, unless other protective measures not available.^{138 150 153 155 156 164 166} If repeat potassium iodide indicated in a pregnant woman, consultation with a clinician recommended^{138 150 153 155 164} and thyroid function monitoring may be indicated in the neonate.¹³⁸

If used during pregnancy or if pregnancy occurs during therapy, apprise patient of potential fetal hazard.¹³⁷

Lactation

Distributed into milk;^{137 138 149 162} possible rash and thyroid suppression in nursing infant.¹³⁷

AAP considers potassium iodide to be compatible with breast-feeding.¹⁵⁷

In radiation emergency, FDA recommends that lactating women receive potassium iodide for their own protection.¹³⁸ However, avoid repeat administration in lactating women unless other protective measures are not available.^{138 150 153 155 164 166} If repeat administration indicated in a nursing woman, consultation with a clinician recommended;^{138 150 153 155 164 166} thyroid function monitoring may be indicated in a breast-fed neonate.¹³⁸

Because radioactive iodine is distributed into milk, some experts (including AAP) recommend that lactating women temporarily not breast-feed after a radiation emergency, unless no alternative is available;¹⁴⁹ breast-feeding can resume when public authorities declare it safe to do so.¹⁴⁹ Consider that administration of potassium iodide to lactating women potentially can reduce the radioiodine content of milk.¹³⁸

Pediatric Use

Safety and efficacy of potassium iodide oral solution containing 1 g/mL (also known as saturated solution of potassium iodide [SSKI]) not established in children.¹³⁷ Has been used for treatment of cutaneous and lymphocutaneous sporotrichosis in children^†;^{108 118 120 172} recommended by IDSA as an alternative for treatment of these infections in children.¹⁶⁹

In radiation emergency, FDA states that benefits of potassium iodide outweigh risks in children, including neonates.¹³⁸ However, to minimize risk of hypothyroidism during critical phase of brain development, avoid repeat administration in neonates ≤1 month of age unless other protective measures not available.^{138 150 153 155 156 164 166} If repeat potassium iodide necessary in neonate ≤1 month of age, consultation with clinician recommended.^{138 150 153 155 164 166}

Monitor neonates for development of hypothyroidism using TSH concentrations and, if indicated, free T₄; initiate thyroid replacement therapy if hypothyroidism occurs.^{138 150 153 155 164}

In radiation emergency, children and neonates unable to tolerate potassium iodide and neonates in whom repeat administration of the drug is a concern should be given priority with regard to other protective measures (e.g., evacuation, sheltering, assurance of uncontaminated milk and food).¹³⁸

Common Adverse Effects

GI effects (stomach upset,¹³⁷ diarrhea,^{137 150 153 155 164} nausea,^{137 150 153 155 164} vomiting,^{137 150 153 155 164} stomach pain^{137 150 153 155 164} ), rash,^{137 150 153 154 155 164} salivary gland swelling^{137 150 153 155 164} or tenderness.¹³⁷

Drug Interactions

Specific Drugs and Laboratory Tests

Potassium Iodide Pharmacokinetics

Absorption

Bioavailability

Dietary iodine is well (>90%) absorbed under normal conditions.¹⁴²

Onset

Effects on thyroid function usually observed within 24 hours after potassium iodide dose and are maximal after 10–15 days of continuous therapy.^a

Duration

When administered during radiation emergency, thyroid protective effect against inhalation or ingestion exposure lasts about 24 hours.^{138 156 166 174}

Distribution

Extent

Distributes selectively into thyroid gland^{142 162} in amounts required for adequate thyroid hormone synthesis.¹⁴² Also distributes to a minor extent into salivary glands, breast, choroid plexus, and gastric mucosa.¹⁴²

Readily crosses placenta;^{137 138 157 162} distributed into milk.^{137 138 149 162}

Elimination

Elimination Route

Iodide not concentrated in thyroid gland is excreted principally in urine.^{142 162} Small amounts excreted in feces and sweat.¹⁴²

Stability

Storage

Oral

Tablets

20–25°C; keep in original foil pack and protect from moisture.^{150 153 164}

Oral Solution

65-mg/mL solution: Tight container at 25°C (may be exposed to 15–30°C); protect from light.¹⁵⁵

1-g/mL solution (also known as saturated solution of potassium iodide [SSKI]): Tight container at 15–30°C; protect from light.¹³⁷ Crystallization may occur if exposed to cold temperatures; crystals will dissolve if solution is warmed and shaken.¹³⁷ Discard if solution turns brownish-yellow.¹³⁷

Extemporaneous oral solution (liquid mixture) prepared using 65- or 130-mg tablets (see Extemporaneous Oral Solutions under Dosage and Administration): Store in refrigerator; discard any unused solution after 7 days.^{140 150 153 164}

Actions

• Iodine participates in a complex series of reactions in the thyroid gland to produce the thyroid hormones T₄ and T₃.¹⁴² Thyroid hormones are essential for human life since they regulate many key biochemical reactions (e.g., protein synthesis, enzymatic activity) and target the developing brain, muscle, heart, pituitary, and kidneys.¹⁴²

• In patients with hyperthyroidism, iodide rapidly inhibits release of thyroid hormones via direct effect on the thyroid gland and inhibits synthesis of thyroid hormones.^{152 a} Also attenuates effects of TSH mediated via cAMP^a and decreases vascularity of thyroid gland.¹⁶¹

• When administered before or promptly after radioactive iodine exposure, potassium iodide blocks or reduces accumulation of radioactive iodine in the thyroid gland.^{138 141}

• Mechanism of action in treatment of cutaneous or lymphocutaneous sporotrichosis caused by S. schenckii not determined.^{143 147 162 169} Does not appear to increase monocyte or neutrophil killing of S. schenckii in vitro;^{143 147} however, exposure of yeast form of S. schenckii to various concentrations of iodine (iodine and potassium iodide solution) in vitro has resulted in rapid cell destruction.^{143 148}

• Mechanism of expectorant activity not clearly established; possibly increases respiratory tract secretions thereby decreasing mucus viscosity.¹³⁷

Advice to Patients

• During radiation emergency, importance of understanding the nature of the radiation hazard and potential benefits and adverse effects of potassium iodide.¹⁴⁹ Importance of taking potassium iodide only as directed by public authorities.^{149 150 153 155 164} Necessity of adhering to other emergency measures recommended by public authorities.^{150 153 155 164}

• If hypersensitivity reaction (e.g., difficulty breathing/speaking/swallowing, shortness of breath, wheezing, rash, swelling of mouth/tongue/throat/face/hands/feet), fever and joint pain, irregular heart beat, or chest pain occurs, immediately discontinue potassium iodide and seek medical care.^{150 153 155 164}

• Importance of women informing clinicians if they are or plan to become pregnant or plan to breast-feed.^{137 149} Advise pregnant women of risks to the fetus.¹³⁷

• Importance of informing clinicians of existing or contemplated concomitant therapy, including prescription and OTC drugs.¹³⁷

• Importance of informing patients of other important precautionary information.¹³⁷ (See Cautions.)

Preparations

Excipients in commercially available drug preparations may have clinically important effects in some individuals; consult specific product labeling for details.

Please refer to the ASHP Drug Shortages Resource Center for information on shortages of one or more of these preparations.

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