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Potassium Iodide

Class: Antithyroid Agents
Note: This monograph also contains information on Strong Iodine Solution
ATC Class: R05CA02
VA Class: RE302
CAS Number: 7681-11-0
Brands: Iosat, SSKI, ThyroSafe, ThyroShield

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.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 (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

Slideshow: OTC Medication Use In Pregnancy: Wise or Worrisome?

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 (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 (localized to skin; also known as fixed cutaneous sporotrichosis) and lymphocutaneous sporotrichosis (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

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.)

Table 1. Recommended Pediatric Dosage of Potassium Iodide for Radiation Emergency (65- or 130-mg Tablets or Oral Solution Containing 65 mg/mL)138150153155156164

Age and Weight

Potassium Iodide Tablets (Iosat, ThyroSafe )

Potassium Iodide Oral Solution Containing 65 mg/mL (Thyroshield)

Birth to 1 month

(See Table 2)

16.25 mg once daily (0.25 mL)

>1 month to 3 years

(See Table 2)

32.5 mg once daily (0.5 mL)

>3 through 12 years

65 mg once daily (one 65-mg tablet or ½ of 130-mg tablet)

65 mg once daily (1 mL)

>12 through 18 years weighing <70 kg (150 lbs)

65 mg once daily (one 65-mg tablet or ½ of 130-mg tablet)

65 mg once daily (1 mL)

>12 through 18 years weighing ≥70 kg (150 lbs)

130 mg once daily (two 65- mg tablets or one 130-mg tablet)

130 mg once daily (2 mL)

Table 2. Recommended Pediatric Dosage of Potassium Iodide for Radiation Emergency (Extemporaneous Oral Solutions)140150153164

Age and Weight

Extemporaneous Oral Solution Containing 8.125 mg/5 mL (8.125 mg/teaspoon)

Extemporaneous Oral Solution Containing 16.25 mg/5 mL (16.25 mg/teaspoon)

Birth to 1 month

16.25 mg once daily (10 mL or 2 teaspoons)

16.25 mg once daily (5 mL or 1 teaspoon)

>1 month to 3 years

32.5 mg once daily (20 mL or 4 teaspoons)

32.5 mg once daily (10 mL or 2 teaspoons)

>3 through 12 years

65 mg once daily (40 mL or 8 teaspoons)

65 mg once daily (20 mL or 4 teaspoons)

>12 through 18 years weighing <70 kg (150 lbs)

65 mg once daily (40 mL or 8 teaspoons)

65 mg once daily (20 mL or 4 teaspoons)

>12 through 18 years weighing ≥70 kg (150 lbs)

Use alternative preparation

130 mg once daily (40 mL or 8 teaspoons)

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

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 recommended138 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 pain137 150 153 155 164 ), rash,137 150 153 154 155 164 salivary gland swelling137 150 153 155 164 or tenderness.137

Interactions for Potassium Iodide

Specific Drugs and Laboratory Tests

Drug or Test

Interaction

Comments

ACE inhibitors (e.g., captopril, enalapril)

Possible hyperkalemia, cardiac arrhythmias, or cardiac arrest137

Antithyroid agents (e.g., methimazole)

Possible additive hypothyroid and goitrogenic effects137 170

Diuretics, potassium-sparing

Possible hyperkalemia, cardiac arrhythmias, or cardiac arrest137

Lithium

Possible additive or synergistic hypothyroid effects128 129 132 133 134 135 136 137 163

Hypothyroidism reported128 131 134 135 136

Generally avoid concomitant use; if used concomitantly, monitor closely for signs and symptoms of hypothyroidism128 129 131 135 136

Potassium-containing drugs

Possible hyperkalemia, cardiac arrhythmias, or cardiac arrest137

Test for thyroid function

Possible altered thyroid function test results137 162

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 gland142 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 cAMPa 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.

Potassium Iodide

Routes

Dosage Forms

Strengths

Brand Names

Manufacturer

Oral

Solution

65 mg/mL

ThyroShield

Fleming

1 g/mL

SSKI

Upsher-Smith

Tablets

65 mg

Iosat (scored)

Anbex

ThyroSafe (scored)

Recipharm

130 mg

Iosat (scored)

Anbex

Strong Iodine Solution

Routes

Dosage Forms

Strengths

Brand Names

Manufacturer

Oral

Solution

Iodine 50 mg/mL and Potassium Iodide 100 mg/mL

Strong Iodine Solution

Lugol’s Solution

Comparative Pricing

This pricing information is subject to change at the sole discretion of DS Pharmacy. This pricing information was updated 06/2014. Actual costs to patients will vary depending on the use of specific retail or mail-order locations and health insurance copays.

SSKI 1GM/ML Solution (UPSHER-SMITH): 237/$163.41 or 474/$308.64

AHFS DI Essentials. © Copyright, 2004-2014, Selected Revisions May 29, 2014. American Society of Health-System Pharmacists, Inc., 7272 Wisconsin Avenue, Bethesda, Maryland 20814.

† Use is not currently included in the labeling approved by the US Food and Drug Administration.

References

100. Becker DV, Braverman LE, Dunn JT et al. The use of iodine as a thyroidal blocking agent in the event of a reactor accident: report of the Environmental Hazards Committee of the American Thyroid Association. JAMA. 1984; 252:659-61. [IDIS 187760] [PubMed 6737670]

101. Federal Emergency Management Agency. Federal policy on distribution of potassium iodide around nuclear power sites for use as a thyroidal blocking agent. Fed Regist. 1985; 50:25624-5.

105. Linnemann RE. Soviet medical response to the Chernobyl nuclear accident. JAMA. 1987; 258:637-43. [IDIS 232447] [PubMed 3302319]

108. Rafal ES, Rasmussen JE. An unusual presentation of fixed cutaneous sporotrichosis: a case report and review of the literature. J Am Acad Dermatol. 1991; 25:928-32. [PubMed 1761772]

112. Rajendran C, Ramesh V, Misra RS et al. Sporotrichosis in Nepal. Int J Dermatol. 1990; 29:716-8. [PubMed 2269567]

118. Frumkin A, Tisserand ME. Sporotrichosis in a father and son. J Am Acad Dermatol. 1989; 20:964-7. [PubMed 2715452]

120. Rudolph RI. Facial sporotrichosis in an infant. Cutis. 1984; 33:171-3,179. [PubMed 6697770]

121. Sperling LC, Read SI. Localized cutaneous sporotrichosis. Int J Dermatol. 1983; 22:525-8. [PubMed 6642845]

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