Potassium iodide Pregnancy and Breastfeeding Warnings

Brand names: Iosat, Pima, SSKI, ThyroShield, Yodefan

Medically reviewed by Drugs.com. Last updated on Aug 4, 2025.

Potassium iodide Pregnancy Warnings

Benefit should outweigh risk.

US FDA pregnancy category: Not assigned

Risk summary: This drug can cause fetal harm, abnormal thyroid function, and goiter when administered to a pregnant woman.

Comments:
-Pregnant women should receive potassium iodide in radiation emergencies for their own protection and for that of their fetus, repeat dosing should be avoided when possible because excess iodine can block fetal thyroid function.
-If this drug is used during pregnancy, or if the patient becomes pregnant while taking this drug, the patient should be apprised of the potential harm to the fetus.

Teratogenic effects such as congenital goiter and hypothyroidism have been reported when iodides have been used by pregnant women. Iodine, whether stable or radioactive, readily crosses the placenta. Throughout pregnancy the number of doses of potassium iodide should be kept to a minimum. If potassium iodide is administered late in pregnancy, the thyroid function of the newborn should be monitored (this is generally met by routine screening). For neonates who have been administered potassium iodide in the first few weeks of life, measure TSH levels and, if necessary, T4 levels; replacement therapy should be administered as appropriate. Pregnant women with active hyperthyroidism must not take potassium iodide because of the risk of fetal thyroid blockage. There are no controlled data in human pregnancy.

US FDA pregnancy category Not Assigned: The US FDA has amended the pregnancy labeling rule for prescription drug products to require labeling that includes a summary of risk, a discussion of the data supporting that summary, and relevant information to help health care providers make prescribing decisions and counsel women about the use of drugs during pregnancy. Pregnancy categories A, B, C, D, and X are being phased out.

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Potassium iodide Breastfeeding Warnings

Benefit should outweigh risk

Excreted into human milk: Yes

Comments:
-Breastfeeding women should receive a dose of potassium iodide to reduce the risk of thyroid cancer in radiation emergencies; repeat dosing should be avoided except during continuing severe contamination.
-Breastfed infants should receive their own dose of potassium iodide in radiation emergencies; repeat dosing should be avoided to minimize the risk of hypothyroidism during the critical phase of brain development.
-Infants receiving potassium iodide during the first month of life should be monitored for the potential development of hypothyroidism (TSH, T4, as indicated).

In the event of radioactive iodine being released into the environment, breastfeeding women and their babies should receive a dose of potassium iodide to reduce their exposure to radioactive iodine. When potassium iodide is used as an adjunct to other public health protective measures during a radioactive emergency, the benefits of potassium iodide are believed to far exceed the risks of side effects. Use of potassium iodide for other indications while breastfeeding is not advised.

See references

Further information

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