https://www.who.int/ionizing_radiation/pub_meet/tech_briefings/potassium_iodide/en/ https://www.who.int/ionizing_radiation/pub_meet/tech_briefin... Tl;dr: "Co

https://www.who.int/ionizing_radiation/pub_meet/tech_briefings/potassium_iodide/en/ https://www.who.int/ionizing_radiation/pub_meet/tech_briefin... Tl;dr: "Commonly known as thyroid blocking, taking potassium iodide (KI)1 before or at the beginning of exposure to radioactive iodine blocks the uptake of radioactive iodine by the thyroid gland, thus reducing exposure of the thyroid to internal radiation. KI does not protect against any other radioactive substances, e.g. radioactive caesium. It is not a generic radiation antidote." "Taking KI shortly before or immediately at the time of exposure to radioactive iodine offers the most effective protection. [...] If taken 4 hours after exposure, protection will be reduced by half; taking KI more than 24 hours after exposure will offer no protection." "A single dose of KI is usually sufficient for adequate protection for 24 hours." "Age group - Mass of KI (mg) - Example of fraction of tablets (130 mg KI tablets) >12 years and adults - 130mg - 1 3 – 12 years - 65mg - 1/2 1 month – 3 years - 32mg - 1/4 Neonate (< 1) - 16mg - 1/8" "The risk of thyroid cancer in children following exposure to radioactive iodine is higher than in adults; younger age groups are at highest risk. As a result, the protection of children must be considered a priority" "During pregnancy, the mother's thyroid gland is metabolically more active than in non-pregnant women, and the amount of radioactive iodine that will be taken up by the thyroid increases in comparison with other adults. The foetal thyroid gland may be exposed to radioactive iodine through the placenta, but will also be protected by the KI taken by the mother. [...] The amount of KI that a breastfeeding woman will provide to an infant through breast milk is not enough to protect the thyroid of an infant exposed to radioactive iodine." "The risk of side effects from KI increases with age, while the risk of radiation-induced thyroid cancer in individuals over 40-years old is low. For this reason, thyroid blocking with KI is not generally indicated in adults over 40 years of age, unless the projected radiation dose to the thyroid rises to levels that threaten the thyroid gland and interfere with its function." "Adverse effects of KI on thyroid function are more frequent in individuals with other, pre-existing thyroid disorders. These disorders are more common in older adults and in the elderly than in children or young adults."