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Potassium iodide oral

Updated 2 Feb 2023 | Antithyroid drugs


Oral formulations of potassium iodide

Drugs List

  • potassium iodide 65mg tablets
  • THYSAT 65mg tablets
  • Therapeutic Indications


    To prevent the uptake of radioactive iodine when not desired



    130 mg potassium iodide once daily. This will protect against radio-iodine exposure lasting up to 24 hours.

    Pregnant and breastfeeding women should take a maximum of two doses.

    Potassium iodate prophylaxis is not usually indicated in adults over 40 years unless doses to the thyroid from inhalation rise to levels threatening thyroid function, that is of the order of about 5 Gy.


    Children 12 years and over
    130 mg potassium iodide (2 tablets) once daily. This will protect against radio-iodine exposure lasting up to 24 hours.

    Children from 3 to 12 years of age
    65 mg potassium iodide (1 tablet) once daily. This will protect against radio-iodine exposure lasting up to 24 hours.

    Children from 1 month to 3 years
    32 mg potassium iodide (half a tablet) once daily. This will protect against radio-iodine exposure lasting up to 24 hours.


    Neonates up to 1 month
    16 mg potassium iodide (quarter of a tablet) once daily. Neonates will not require further doses.


    Pregnancy - Active hyperthyroidism

    Precautions and Warnings

    Heat cramp
    Adrenal insufficiency
    Renal impairment
    Severe dehydration
    Thyroid dysfunction

    Neonate exposed in utero: Monitor thyroid function
    Neonate: Monitor TSH and T4 levels - consider replacement therapy
    Hyperthyroidism may be exacerbated or precipitated
    Breastfeeding: Maximum of two doses
    Pregnancy: Maximum of two doses

    In cases of exposure to radioactive iodine from nuclear accidents, dosing of potassium iodide should be based on emergency plans and predetermined operational intervention levels. Risk benefit of administration of stable radioactive iodine should be considered for different age groups at risk. Pregnant and breastfeeding women, infants and children should be treated first. Followed by patients with thyrotoxicosis or a past history of thyrotoxicosis as they may also be at increased risk from exposure to radio-iodine.

    Potassium iodide is most suitable for inhaled radioactive iodine and should not be used as the main prophylactic treatment against ingested iodine contamination.

    The potential benefit of iodine prophylaxis is greatest in the young. The thyroid function of the foetus, neonate and young infant has a higher yearly thyroid cancer risk per unit dose of radioactive iodine than the thyroid of an adult.

    Neonates in the first days of life are at particular risk of exposure to radio iodine and blocking of thyroid function by overload of potassium iodide. The fraction of radioactive uptake is fourfold greater than all other age groups. Transient hypothyroidism during this early period of brain development can result in loss of intellectual capacity. If stable iodine is given to neonates close follow up of thyroid function is essential. For neonates who have been administered potassium iodide in the first few weeks of life TSH levels and, if necessary, T4 levels should be monitored and appropriate replacement therapy given.

    Pregnancy and Lactation


    Pregnant women should receive no more than two doses of potassium iodide.
    Contraindicated in pregnant women with active hyperthyroidism due to the increased risk of foetal thyroid blockage.

    Teratogenic effects such as congenital goitre and hypothyroidism have been reported when iodides, are administered to pregnant women. However in the event of a nuclear accident, the use of potassium iodide in low doses over a short period of time, as a thyroid blocking agent is not contraindicated.

    When used prophylactically, administration of potassium iodide to the pregnant mother should also provide protection to the foetus.

    The dosage during pregnancy should be kept to a minimum. In areas of iodine deficiency prolonged dosage could lead to maternal or foetal thyroid blockage with consequences for foetal development. If potassium iodide is administered late in pregnancy, the thyroid function of the newborn should be monitored. This is generally met by routine screening in the neonatal period.

    The use of all medication in pregnancy should be avoided whenever possible; particularly in the first trimester. Non-drug treatments should also be considered. When essential, a medication with the best safety record over time should be chosen, employing the lowest effective dose for the shortest possible time. Polypharmacy should be avoided. Teratogens taken in the pre-embryonic period, often quoted as lasting until 14-17 days post-conception, are believed to have an all-or-nothing effect. Where drugs have a short half-life, and when the date of conception is certain, this may allow women to be reassured where drug exposure has occurred within this time frame. Further advice may be available from the UK National Teratology Information Service (NTIS) and through ToxBase, available via password on the internet ( ) or if this is unavailable at the backup site ( ).


    Breastfeeding mothers should receive no more than two doses of potassium iodide.

    Iodine is actively transported into breast milk. Breast feeding should continue during treatment with potassium iodide.

    Neonates, infants born prematurely, those with low birth weight, those with an unstable gastrointestinal function or who have serious illnesses may require special consideration. For any infant, if a drug is prescribed to the nursing mother, it should be at the lowest practical dose and for the shortest time. When drug administration is unavoidable and breastfeeding is to continue, minimisation of exposure of the infant to the drug may sometimes be achieved by timing the maternal doses to just after a feeding episode. Infants exposed to drugs via breast milk should be monitored for unusual signs or symptoms. Interactions between the drug received by the infant from the mother's milk and medication prescribed for the infant should also be considered, for example, when the drug given to the infant may prevent metabolism of the drug received via breast milk.
    Specialist advice is available from the UK Drugs in Lactation Advisory Service at

    Side Effects

    Gastro-intestinal symptoms
    Hypersensitivity reactions
    Iodine induced autoimmunity
    Iodine induced hypothyroidism
    Salivary gland enlargement


    It is strongly recommended that the UK National Poisons Information Service be consulted on cases of suspected or actual overdose where there is doubt over the degree of risk or about appropriate management.

    The following number will direct the caller to the relevant local centre (0844) 892 0111

    Information may be obtained if you have access to ToxBase the primary clinical toxicology database of the National Poisons Information Service. This is available via password on the internet ( ) or if this is unavailable at the backup site ( ).

    Further Information

    Last Full Review Date: June 2013

    Reference Sources

    Drugs During Pregnancy and Lactation: Treatment Options and Risk Assessment, 2nd edition (2007) ed. Schaefer, C., Peters, P. and Miller, R. Elsevier, London.

    Martindale: The Complete Drug Reference, 37th edition (2011) ed. Sweet man, S. Pharmaceutical Press, London.

    Summary of Product Characteristics: ThySat Tablets 65mg. Hameln Pharmaceuticals Ltd. Revised January 2013.

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