What is the dosage and administration of Thyrosafe (potassium iodide) for adults and children in cases of potential radiation exposure?

Thyrosafe (Potassium Iodide) Dosing for Radiation Exposure

Adults over 18 years should take 130 mg (2 mL) daily, while children receive weight- and age-based doses ranging from 16.25 mg for newborns to 130 mg for adolescents weighing ≥150 pounds, administered as a single daily dose only when directed by public officials during a confirmed radioactive iodine emergency. 1

Age-Based Dosing Algorithm

Adults and Adolescents

• Adults over 18 years: 130 mg (2 mL) once daily 1
• Adolescents 12-18 years weighing ≥150 pounds: 130 mg (2 mL) once daily 1
• Adolescents 12-18 years weighing <150 pounds: 65 mg (1 mL) once daily 1

Pediatric Populations

• Children 3-12 years: 65 mg (1 mL) once daily 1
• Children 1 month to 3 years: 32.5 mg (0.5 mL) once daily 1
• Newborns (birth to 1 month): 16.25 mg (0.25 mL) once daily 1

Critical Timing Considerations

Administer potassium iodide as soon as possible after public officials direct you to do so, ideally within 4 hours of radioactive iodine exposure to achieve approximately 50% reduction in thyroid uptake. 2, 3

• Maximum protective effect occurs when administered within 6 hours of exposure 3, 4
• Efficacy decreases significantly if delayed beyond this window 4
• When administered just before exposure, KI blocks at least 95% of thyroid radiation dose 5

Repeat Dosing Protocol

• Take only ONE dose per 24-hour period 1
• If repeat dosing is necessary, wait exactly 24 hours after the first dose 1
• Continue daily dosing only as long as public officials direct, until risk of major radioactive iodine exposure ceases 1
• In cases of continued or repeated radioiodine release, daily dosing up to 1 week may be necessary and is not harmful 6
• Daily doses of 15 mg can maintain thyroid blockade above 90% during persistent exposure 5

High-Risk Population Considerations

Children and Adolescents

• This age group requires the most stringent protection measures due to markedly higher sensitivity to radiation-induced thyroid cancer 2, 7
• The risk of radiation-induced thyroid cancer justifies KI prophylaxis despite potential hypothyroidism risk, especially in newborns 5
• Newborns and babies may be more sensitive to side effects and require monitoring 6

Pregnant Women

• Pregnant women should receive the same adult dose (130 mg) as the most important factor for fetal survival is maternal survival 2
• Use cautiously, especially after the first trimester, as KI can affect the fetal thyroid 3
• The fetal thyroid is more iodine-avid than the adult thyroid, resulting in higher radiation doses during maternal exposure 2
• Any pregnant woman exposed to more than 0.25 Gy of radiation requires fetal dose estimation by a health physicist 2

Critical Safety Warnings

When NOT to Use Potassium Iodide

Potassium iodide is NOT a generic antiradiation drug and should only be used for confirmed radioiodine exposure. 2

• In "dirty bomb" scenarios, radioiodines are extremely unlikely to be present due to their short 8.5-day half-life 2
• KI administration in these inappropriate cases risks life-threatening anaphylaxis without benefit 2
• Individuals with iodine allergy history may experience severe allergic reactions including anaphylaxis 2, 3

Monitoring Requirements

• Monitor patients for side effects, particularly thyroid dysfunction and allergic manifestations 3
• Stop KI immediately if severe side effects occur 3
• Do not exceed one dose per 24 hours, as more will not provide additional protection and increases side effect risk 1

Common Pitfalls to Avoid

• Never take more than one dose in 24 hours - the thyroid can only "hold" certain amounts of iodine, and excess increases side effects without benefit 1
• Do not use for general radiation exposure - only effective for radioactive iodine, not other radiation types 2
• Do not delay administration - effectiveness drops dramatically after 6 hours post-exposure 3, 4
• In iodine-deficient populations, radioiodine uptake risk is higher, making timely KI administration even more critical 6, 8