Potassium Iodide (Systemic)


VA CLASSIFICATION
Primary: HS852
Secondary: AD900; AM700; TN499

Commonly used brand name(s): Iosat; Pima; Thyro-Block.

Other commonly used names are
KI and SSKI .
Note: For a listing of dosage forms and brand names by country availability, see Dosage Forms section(s).



Category:


Antihyperthyroid agent—

radiation protectant (thyroid gland)—

thyroid inhibitor—

antifungal (systemic)—

iodine replenisher—

Indications

Note: Bracketed information in the Indications section refers to uses that are not included in U.S. product labeling.

Accepted

Hyperthyroidism (treatment)1—Potassium iodide is indicated in the treatment of hyperthyroidism. {05}

Radiation protection, thyroid gland—Potassium iodide is indicated as a radiation protectant (thyroid gland) prior to and following oral {25} administration or inhalation {25} of radioactive isotopes of iodine {03} or in radiation emergencies.

[Erythema nodosum (treatment)]1—Potassium iodide is used in the treatment of erythema nodosum. {09} {16}

[Iodine deficiency (treatment)]1—Potassium iodide is used in the treatment of iodine deficiency.

[Sporotrichosis, cutaneous lymphatic (treatment)]1—Potassium iodide is used in the treatment of cutaneous lymphatic sporotrichosis. {01} {17} {18}

[Thyroid involution, preoperative]1—Potassium iodide is used concurrently with an antithyroid agent to induce thyroid involution prior to thyroidectomy. {02}

Unaccepted
Potassium iodide has not been shown to have a clinically significant expectorant action.

1 Not included in Canadian product labeling.



Pharmacology/Pharmacokinetics

Physicochemical characteristics:
Molecular weight—
    166.00

Mechanism of action/Effect:


Antihyperthyroid agent:

In hyperthyroid patients, potassium iodide produces rapid remission of symptoms by inhibiting the release of thyroid hormone into the circulation. The effects of potassium iodide on the thyroid gland include reduction of vascularity, a firming of the glandular tissue, shrinkage of the size of individual cells, reaccumulation of colloid in the follicles, and increases in bound iodine. These actions may facilitate thyroidectomy when the medication is given prior to surgery. {10}



Radiation protectant:

When administered prior to and following administration of radioactive isotopes and in radiation emergencies involving the release of radioactive iodine {25}, potassium iodide protects the thyroid gland by blocking the thyroidal uptake of radioactive isotopes of iodine. {11} {12}

When potassium iodide is administered simultaneously with radiation exposure, the protectant effect is approximately 97%. Potassium iodide given 12 and 24 hours before exposure yields a 90% and 70% protectant effect, respectively. However, potassium iodide administered 1 and 3 hours after exposure results in an 85% and 50% protectant effect, respectively. Potassium iodide administered more than 6 hours after exposure is thought to have a negligible protectant effect. {22}



Precautions to Consider

Pregnancy/Reproduction

Potassium iodide crosses the placenta; use during pregnancy may result in abnormal thyroid function and/or goiter in the infant. {13} {14} {19}

Breast-feeding

Potassium iodide is distributed into breast milk; use by nursing mothers may cause skin rash and thyroid suppression in the infant. {13} {14}

Pediatrics

Potassium iodide may cause skin rash and thyroid suppression in infants. Appropriate studies have not been performed for use as a systemic antifungal. {19}


Geriatrics


Appropriate studies on the relationship of age to the effects of potassium iodide have not been performed in the geriatric population. However, geriatrics-specific problems that would limit the usefulness of this medication in the elderly are not expected.


Dental

Potassium iodide may cause salivary gland swelling or tenderness, burning of mouth or throat, metallic taste, soreness of teeth and gums, and unusual increase in salivation. {15}

Drug interactions and/or related problems
The following drug interactions and/or related problems have been selected on the basis of their potential clinical significance (possible mechanism in parentheses where appropriate)—not necessarily inclusive (» = major clinical significance):


Note: Combinations containing any of the following medications, depending on the amount present, may also interact with this medication.

» Antithyroid agents    (concurrent use of these medications with potassium iodide may potentiate the hypothyroid and goitrogenic effects of antithyroid agents or potassium iodide; baseline thyroid status should be determined at periodic intervals to detect changes in the thyroid-pituitary response)

    (since potassium iodide may decrease the effectiveness of thioamides in thyroid storm, potassium iodide should be given one hour prior to thioamides{36})


Captopril or
Enalapril or
Lisinopril    (concurrent use of captopril, enalapril, or lisinopril with potassium iodide may result in hyperkalemia; serum potassium concentrations should be monitored {31}, however usual doses of potassium iodide used for radiation protection (i.e. up to 130 mg) contain negligible amounts of potassium and should not constitute a problem with ACE inhibitors{36})


» Diuretics, potassium-sparing    (concurrent use with potassium iodide may increase the effects of potassium, possibly resulting in hyperkalemia and cardiac arrhythmias or cardiac arrest; serum potassium concentrations should be monitored {08} {29} {30} {32})


» Lithium    (concurrent use with potassium iodide may potentiate the hypothyroid and goitrogenic effects of either medication; baseline thyroid status should be determined at periodic intervals to detect changes in the thyroid-pituitary response {12} {32})


Sodium iodide I 131, therapeutic     (potassium iodide may decrease thyroidal uptake of I 131 {34})



Laboratory value alterations
The following have been selected on the basis of their potential clinical significance (possible effect in parentheses where appropriate)—not necessarily inclusive (» = major clinical significance):

With diagnostic test results
Thyroid function studies
Thyroid imaging, radionuclide and
Thyroid uptake tests    (potassium iodide may decrease thyroidal uptake of I 131, I 123, and sodium pertechnetate Tc 99m {33} {34})


Medical considerations/Contraindications
The medical considerations/contraindications included have been selected on the basis of their potential clinical significance (reasons given in parentheses where appropriate)— not necessarily inclusive (» = major clinical significance).


Risk-benefit should be considered when the following medical problems exist
» Hyperkalemia {21}    (condition may be exacerbated)


Hyperthyroidism (for use other than thyroid inhibitor)    (prolonged use of iodine may cause thyroid gland hyperplasia, thyroid adenoma, goiter, or hypothyroidism {24})


Myotonia congenita    (condition may be exacerbated by potassium {27})


» Renal function impairment {08}    (may cause excessive serum potassium concentrations {21})


Sensitivity to potassium iodide {08}
Tuberculosis {21}    (may cause irritation and increase secretions {24})



Patient monitoring
The following may be especially important in patient monitoring (other tests may be warranted in some patients, depending on condition; » = major clinical significance):

Serum potassium concentrations {08}    (recommended at periodic intervals during therapy in patients with renal function impairment)




Side/Adverse Effects
The following side/adverse effects have been selected on the basis of their potential clinical significance (possible signs and symptoms in parentheses where appropriate)—not necessarily inclusive:

Those indicating need for medical attention
Incidence less frequent {08} {10}
    
Allergic reactions, specifically angioedema (swelling of the arms, face, legs, lips, tongue, and/or throat)
    
arthralgia (joint pain)
    
eosinophilia
    
swelling of lymph nodes
    
urticaria (hives)

With prolonged use {08} {10}
    
Iodism {23}(burning of mouth or throat; gastric irritation; increased watering of mouth; metallic taste; severe headache; skin lesions; soreness of teeth and gums; symptoms of head cold)
    
potassium toxicity (confusion; irregular heartbeat; numbness, tingling, pain, or weakness in hands or feet; unusual tiredness; weakness or heaviness of legs){08}{10}



Those indicating need for medical attention only if they continue or are bothersome
Incidence less frequent
    
Diarrhea
    
nausea or vomiting {05}
    
stomach pain {05}





Patient Consultation
As an aid to patient consultation, refer to Advice for the Patient, Potassium Iodide (Systemic).

In providing consultation, consider emphasizing the following selected information (» = major clinical significance):

Before using this medication
»   Conditions affecting use, especially:
Sensitivity to iodine or potassium iodide

Pregnancy—May cause thyroid problems or goiter in the newborn infant





Breast-feeding—May cause skin rash and thyroid problems in nursing babies





Use in children—May cause skin rash and thyroid problems in nursing infants






Dental—May cause swelling of salivary glands, burning of mouth or throat, metallic taste, soreness of teeth and gums, or increase in salivation
Other medications, especially antithyroid agents, diuretics (potassium sparing), or lithium
Other medical problems, especially hyperkalemia or renal function impairment

Proper use of this medication
» Taking after meals or with food or milk to minimize gastrointestinal irritation

Proper administration technique for oral liquids:
Taking medication by mouth even if dispensed in a dropper bottle

Not using if solution turns brownish yellow

Taking medication in a full glass (240 mL) of water or in fruit juice, milk, or broth to improve taste and lessen gastric upset; drinking full dose

If crystals form in solution, warming closed container in warm water and gently shaking container

Proper administration technique for uncoated tablets:
Dissolving each tablet in 1/2 glass (120 mL) of water or milk before taking; drinking full dose
» Compliance with full course of therapy (fungal infections)

» Proper dosing
Missed dose: Taking as soon as possible; not taking if almost time for next dose; not doubling doses

» Proper storage

For use as a radiation protectant (thyroid gland)
Taking medication only upon instructions from state or local health authorities

» Taking medication daily until significant risk of exposure to radioiodines by inhalation or ingestion no longer exists, unless otherwise instructed; not taking more medication or more often than instructed

Precautions while using this medication
Regular visits to physician to check progress during therapy

» Caution in patients on potassium-restricted diet


Side/adverse effects
Signs of potential side effects, especially allergic reactions, iodism, or potassium toxicity


General Dosing Information
The potassium content is 6 mEq (234 mg) per gram of potassium iodide. {10}

To minimize stomach upset, the medication may be administered after meals and at bedtime with food or milk. {10}

To protect against possible gastrointestinal injury, which has been associated with the oral ingestion of concentrated potassium salt preparations, {21} it is recommended that the oral solution be administered in a full glass (240 mL) of water, or in fruit juice, milk, or broth. It is also recommended that each regular tablet be dissolved in 1/2 glass (120 mL) of water or milk before ingestion. {10}

Prolonged use may result in hypothyroidism, parotitis, iodism, and, particularly in postpubescent patients, acneiform skin lesions. {21}

In an emergency, when the graded dose method (described in the pediatric dosing section below) cannot be arranged, the 130-mg dose may be used safely for patients of all ages except the smallest infants. {35}{36}


Oral Dosage Forms

Note: Bracketed uses in the Dosage Forms section refer to categories of use and/or indications that are not included in U.S. product labeling.

POTASSIUM IODIDE ORAL SOLUTION USP

Usual adult and adolescent dose
Antihyperthyroid agent 1
Oral, 250 mg three times a day. {26}

Radiation protectant (thyroid gland)
Oral, 130 mg once a day, until significant risk of exposure to radioiodines by inhalation or ingestion no longer exists. {35}

[Antifungal (systemic)]1
Oral, 600 mg three times a day, the dosage being increased by 60 mg at each dose until the maximum tolerated dose is reached. {17}

[Iodine replenisher ]1
Oral, 5 to 10 mg per day. {20}

[Thyroid inhibitor—Thyroid involution, preoperative]1: Prior to thyroidectomy
Oral, 5 drops of a 1-gram-per-mL solution (approximately 250 mg) three times a day for ten days before surgery, usually administered concurrently with an antithyroid agent. {10}


Usual adult prescribing limits
Up to 12 grams daily.

Usual pediatric dose
Radiation protectant (thyroid gland)
   • Infants through 1 month of age: Oral, 16 mg once a day, until significant risk of exposure to radioiodines by inhalation or ingestion no longer exists. {35}
   • Infants and children over 1 month through 3 years of age: Oral, 32 mg once a day, until significant risk of exposure to radioiodines by inhalation or ingestion no longer exists. {35}
   • Children and adolescents over 3 years through 18 years of age (less than 70 kg of body weight): Oral, 65 mg once a day, until significant risk of exposure to radioiodines by inhalation or ingestion no longer exists. {35}
   • Adolescents over 12 years through 18 years of age approaching adult size (70 kg or greater of body weight): See Usual adult and adolescent dose.{35}

Note: Infants may be more sensitive to thyroid suppression by iodide. Repeat dosing should be avoided if sheltering and evacuation are possible and significant enough to prevent exposure.{36}


[Antifungal (systemic)]1
Dosage has not been established.

[Iodine replenisher ]1
Oral, 1 mg per day.

[Thyroid inhibitor—Thyroid involution, preoperative]1
See Usual adult and adolescent dose.


Strength(s) usually available
U.S.—


1 gram per mL (Rx)[Generic]{06}

Packaging and storage:
Store below 40 °C (104 °F), preferably between 15 and 30 °C (59 and 86 °F), unless otherwise specified by manufacturer. Store in a tight, light-resistant container. Protect from freezing.

Stability:
Crystallization may occur under normal conditions of storage, especially if refrigerated; however, on warming and shaking, the crystals will redissolve. {21}

Free iodine may be liberated by oxidation of the potassium iodide, causing the solution to turn brownish yellow in color. If this occurs, the solution should be discarded. {21}

Auxiliary labeling:
   • For oral use only.
   • Do not refrigerate.
   • Continue medicine for full time of treatment (antifungal).


POTASSIUM IODIDE SYRUP

Usual adult and adolescent dose
Radiation protectant (thyroid gland)
Oral, 130 mg once a day, until significant risk of exposure to radioiodines by inhalation or ingestion no longer exists. {35}

[Antifungal (systemic)]1
Oral, 600 mg three times a day, the dosage being increased by 60 mg at each dose until the maximum tolerated dose is reached. {17}

[Iodine replenisher ]1
Oral, 5 to 10 mg per day. {20}

[Thyroid inhibitor—Thyroid involution, preoperative]1: Prior to thyroidectomy
Oral, 4 mL (approximately 260 mg) three times a day for ten days before surgery, usually administered concurrently with an antithyroid agent. {10}


Usual adult prescribing limits
Up to 12 grams daily.

Usual pediatric dose
Radiation protectant (thyroid gland)
   • Infants through 1 month of age: Oral, 16 mg once a day, until significant risk of exposure to radioiodines by inhalation or ingestion no longer exists. {35}
   • Infants and children over 1 month through 3 years of age: Oral, 32 mg once a day, until significant risk of exposure to radioiodines by inhalation or ingestion no longer exists. {35}
   • Children and adolescents over 3 years through 18 years of age (less than 70 kg of body weight): Oral, 65 mg once a day, until significant risk of exposure to radioiodines by inhalation or ingestion no longer exists. {35}
   • Adolescents over 12 years through 18 years of age approaching adult size (70 kg or greater of body weight): See Usual adult and adolescent dose.{35}
Note: Infants may be more sensitive to thyroid suppression by iodide. Repeat dosing should be avoided if sheltering and evacuation are possible and significant enough to prevent exposure.{36}



[Antifungal (systemic)]1
Dosage has not been established.

[Iodine replenisher ]1
Oral, 1 mg per day.

[Thyroid inhibitor—Thyroid involution, preoperative]1
See Usual adult and adolescent dose.


Strength(s) usually available
U.S.—


325 mg per 5 mL (Rx) [Pima{06}]

Packaging and storage:
Store below 40 °C (104 °F), preferably between 15 and 30 °C (59 and 86 °F), in a well-closed container, unless otherwise specified by manufacturer. Protect from freezing.

Auxiliary labeling:
   • For oral use only.
   • Continue medicine for full time of treatment (for 3-day uncinariasis treatment).

Note: When dispensing, include a calibrated liquid-measuring device.



POTASSIUM IODIDE TABLETS USP

Usual adult and adolescent dose
Radiation protectant (thyroid gland)
Oral, 130 mg once a day, until significant risk of exposure to radioiodines by inhalation or ingestion no longer exists. {35}

[Antifungal (systemic)]1
Oral, 600 mg three times a day, the dosage being increased by 60 mg at each dose until the maximum tolerated dose is reached. {17}

[Iodine replenisher ]1
Oral, 5 to 10 mg per day.

[Thyroid inhibitor—Thyroid involution, preoperative]1: Prior to thyroidectomy
Oral, Dissolve 2 tablets (approximately 260 mg) in 1 glassful of water, three times a day for ten days before surgery, usually administered concurrently with an antithyroid agent. {10}


Usual adult prescribing limits
Up to 12 grams daily.

Usual pediatric dose
Radiation protectant (thyroid gland)
   • Infants through 1 month of age: Oral, 16 mg once a day, until significant risk of exposure to radioiodines by inhalation or ingestion no longer exists. {35}
   • Infants and children over 1 month through 3 years of age: Oral, 32 mg once a day, until significant risk of exposure to radioiodines by inhalation or ingestion no longer exists. {35}
   • Children and adolescents over 3 years through 18 years of age (less than 70 kg of body weight): Oral, 65 mg once a day, until significant risk of exposure to radioiodines by inhalation or ingestion no longer exists. {35}
   • Adolescents over 12 years through 18 years of age approaching adult size (70 kg or greater of body weight): See Usual adult and adolescent dose.{35}

Note: Infants may be more sensitive to thyroid suppression by iodide. Repeat dosing should be avoided if sheltering and evacuation are possible and significant enough to prevent exposure.{36}


[Antifungal (systemic)]1
Dosage has not been established.

[Iodine replenisher ]1
Oral, 1 mg per day. {17}

[Thyroid inhibitor—Thyroid involution, preoperative]1
See Usual adult and adolescent dose.


Strength(s) usually available
U.S.—


130 mg (Rx) [Thyro-Block{35}]


130 mg (Rx) [Iosat{35}]

Note: Thyro-Block is distributed strictly to state, local, and federal agencies, nuclear power plants, and hospitals. Both Thyro-Block and Iosat should be used only in radiation emergencies.{35}{36}


Canada—


130 mg (Rx) [Thyro-Block{07}]

Packaging and storage:
Store below 40 °C (104 °F), preferably between 15 and 30 °C (59 and 86 °F), unless otherwise specified by manufacturer. Store in a tight container.

Preparation of dosage form:
To prepare lower doses of potassium iodide, a 130-mg tablet may be dissolved in 240 mL (8 ounces) of liquid. The final concentration of the solution that is administered to the patient is 0.54 mg per mL (16 mg per ounce). Therefore, 30 mL of the solution would result in a 16 mg dose.{35}{36} The FDA is planning to conduct studies of the palatability, solubility, and stability of potassium iodide dissolved in a number of different liquids, including juice and formula.{35}

Auxiliary labeling:
   • Dissolve in liquid before taking.
   • Continue medicine for full time of treatment (for 3-day uncinariasis treatment).


POTASSIUM IODIDE DELAYED-RELEASE TABLETS USP

Note: Potassium Iodide delayed-release tablets are not recommended since the administration of this dosage form has been associated with small bowel lesions, which can cause obstruction, hemorrhage, perforation, and possibly death.


Strength(s) usually available
U.S.—


300 mg (Rx)[Generic]



Revised: 08/15/2002



References
  1. Hay R. Managing fungal infections. Brit J Hosp Med 1984; 31: 378-80.
  1. Feek C, Sawers J, Irvine J, Beckett G, Ratcliffe W, Toft A. Combination of potassium iodide and propranolol in preparation of patients with Graves' disease for thyroid surgery. N Eng J Med 1980; 302: 883-5.
  1. Reviewer comments, Potassium Iodide (Systemic), USP DI Review, Nov/Dec 1984.
  1. Thyro-Block product information, Wallace (U.S.), rev 2/85, Rec 1/86.
  1. Potassium iodide solution product information, Lyne Labs, rec 2/86, rev 2/84, U.S.
  1. Redbook 1989, Potassium iodide (generic), p 563, 573.
  1. CPS 1988, Thyro-block (Horner).
  1. Package insert, Potassium iodide, (Lilly), Rev 6/88, Rec 1/89.
  1. Schulz R, Whiting D. Treatment of erythema nodosum and nodular vasculitis with potassium iodide. Br J Dermatol 1976; 94: 75-8.
  1. AHFS, 1990
  1. Goodman and Gilman, The pharmacological Basis of Therapeutics, 7th edition, 1985.
  1. AMA DE, 6th edition, 1986.
  1. Handbook of Clinical Drug Data, 6th edition, 1988.
  1. Niebyl J. Drug use in pregnancy, 1982.
  1. Accepted Dental Therapeutics, 40th edition, 1984.
  1. Horio T, Ofuji S. Potassium iodide in erythema nodosum and other erythematous dermatoses. J Am Academy Derm 1983, 9[1]: 77-81.
  1. Grekin R, Sporotrichosis. J Am Academy Derm 1984, 10[2, part 1]: 233-4.
  1. Nusbaum B, et al. Sporotrichosis acquired from a cat. J Am Academy Derm. 1983, 8: 386-91.
  1. Drug-induced goiters in the fetus and in children and adults. Medical Letter 7/24/70.
  1. Panelist comment, 1985 review cycle.
  1. SSKI product information, rev 2/84, rec 2/86, Lyne Labs.
  1. Cooper R. Potassium iodide for radiation exposure. DICP 1988; 22: 33-4.
  1. Panel comment, 1991 revision cycle.
  1. Panel comment from Strong Iodine monograph, 1991 revision cycle.
  1. Panel comment, 1991 revision cycle.
  1. Panel comment, 1991 revision cycle.
  1. Panel comment, 1991 revision cycle.
  1. Manufacturer comments, 1991 revision cycle.
  1. Aldactone product information, Searle, rec 1/90, rev 9/89, Canada.
  1. Dyrenium product information, SKF, rec 5/89, rev 1/88, U.S.
  1. Capoten product information, Squibb, 1991 PDR, p 2142.
  1. Drug Information Facts, 1990.
  1. Hladik W, Saha G, Study K. Essentials of nuclear medicine science. William and Wilkins Press, 1987, p 184.
  1. Reviewer comment, on Strong Iodine monograph, 1990 revision.
  1. The Food and Drug Administration Public Health Advisory: Potassium Iodide as a Thyroid Blocking Agent in Radiation Emergencies. (12/10/2001). Retrieved May 3, 2002, from the World Wide Web: http://www.fda.gov/cder/guidance/4825fnl.htm.
  1. Expert Committee comment, 07/2002.
Hide
(web1)