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Potassium iodate

Updated 2 Feb 2023 | Antithyroid drugs

Drugs List

  • potassium iodate 85mg tablets
  • Therapeutic Indications


    For use as a thyroid blocking agent to prevent the uptake of radioactive iodine by the thyroid, for example following a nuclear incident.



    Administer 170mg of potassium iodate (equivalent to 100mg iodine) as a single daily dose. This will protect against exposure for up to 24 hours.


    See adult dosage.


    3 to 12 years
    Administer 85mg of potassium iodate (equivalent to 50mg iodine) as a single daily dose.

    1 month to 3 years
    Administer 42.5mg of potassium iodate (equivalent to 25mg iodine) as a single daily dose. This is half a 85mg potassium iodate tablet.


    See adult dosage.


    Administer 21.25mg of potassium iodate (equivalent to 12.5mg iodine) as a single daily dose. This is a quarter of a 85mg potassium iodate tablet.

    Alternatively 12.5mg iodine equivalent should be given as a standard solution preparation where possible.

    For neonates living at home a dosage of a quarter of a 85mg tablet is satisfactory. The dosage can be crushed and mixed with milk or water. For neonates in hospital a dosage of 12.5mg iodine equivalent can be given as a standard solution freshly prepared from potassium iodine crystals. It is recommended that maternity wards store potassium iodine crystals.

    Patients with Renal Impairment

    Contraindicated in patients with renal failure.

    Use with caution in patients with renal impairment.

    Additional Dosage Information

    In order for the uptake of radioactive iodine to be blocked, doses should be taken within 3 hours of exposure, although dosing within 10 hours will provide some protection.

    A single dose of potassium iodate gives adequate protection for one day. Prolonged exposure may require repeat dosing.


    For oral administration.

    For children half of one tablet may be crushed and mixed with jam, honey or yoghurt.

    In neonates a quarter of one tablet can be crushed and mixed with milk or juice before administration.

    Precautions and Warnings

    In cases of exposure to radioactive iodine from nuclear accidents, dosing of potassium iodate 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.

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

    Use with caution in patients with thyrotoxicosis who are being treated medically or patients who previously suffered from thyrotoxicosis where their treatment is completed and they are in remission.

    Iodine induced hyperthyroidism may be precipitated in patients with asymptomatic nodular goitre or latent Graves disease who are not under medical care.

    Potassium salts should be given cautiously to patients with renal impairment, adrenal insufficiency, acute dehydration or heat cramp.

    Use potassium salts with caution in patients receiving potassium sparing diuretics concurrently as hyperkalaemia may occur.

    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.

    Potassium iodate prophylaxis is not usually indicated in adults over 40years unless doses to the thyroid from inhalation rise to levels threatening thyroid function, that is of the order of about 5 Gy. The risk of thyroid cancer is extremely low in this group whereas the incidence of thyroid disease is higher in this age group therefore the risk of iodine induced thyroid complications are higher.

    Neonates in the first days of life are at particular risk of exposure to radioiodine and blocking of thyroid function by overload of potassium iodate. The fraction of radioactive uptake is fourfold greater than all other age groups. The neonatal thyroid is especially sensitive to functional blocking caused by overload of potassium iodate. 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 iodate in the first few weeks of life TSH levels and, if necessary, T4 levels should be monitored and appropriate replacement therapy given.

    Pregnancy (see Pregnancy section)

    Pregnancy and Lactation


    Teratogenic effects such as congenital goitre and hypothyroidism have been reported when iodides, and therefore presumably iodate, are administered to pregnant women.

    However in the event of a nuclear accident, the use of potassium iodate in low doses over a short period of time, as a thyroid blocking agent is not contraindicated.

    When used prophylactically, administration of potassium iodate 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 iodate 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. For neonates who have been administered potassium iodate in the first few weeks of life TSH levels and, if necessary T4 levels should be monitored and appropriate replacement therapy given.

    Pregnant women with active hyperthyroidism should not be treated with potassium iodate due to the increased risk of foetal thyroid blockage.

    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 ( ).


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

    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

    Experience with the use of potassium iodate is limited, therefore it is presumed that the side effects that may occur with potassium iodine can be associated with potassium iodate.

    Hypersensitivity reactions such as skin rashes, swollen salivary glands, headache and bronchospasm.
    Gastrointestinal disturbances- these may vary in severity and be dose dependant.
    Iodine induced autoimmunity (Graves and Hashimoto type)
    Toxic nodular goitre
    Iodine induced hypothyroidism
    Overactive thyroid gland
    Enlarged thyroid gland
    Possible development of myxoedema
    Continual administration may lead to mental depression, nervousness, sexual impotence and insomnia.


    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 ( ).

    Shelf Life and Storage

    Do not store above 25 degrees C
    Store in original container

    Further Information

    Last Full Review Date: November 2011

    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: Potassium Iodate Tablets 85mg. Alliance Pharmaceuticals Ltd. Revised January 2011.

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