Thyro-Block (Potassium Iodide)


Carter Horner

Potassium Iodide

Thyroid Blocking Agent

Action and Clinical Uses:

Potassium iodide, an ionic thyroid blocking agent, acts on the transport of iodide into and out of the thyroid. When given in sufficient amounts, entry of radioiodide into the gland can be virtually prevented.

The onset of inhibition is rapid and is readily demonstrated 30 minutes after oral administration. An important factor in obtaining satisfactory acute block of radioiodine uptake is the speed of iodide administration after exposure to radioiodine. It is clear from standard uptake curves that, after a single pulse of radioiodine, the bulk of it has entered the gland by 10 to 12 hours and little benefit may be expected by blocking beyond this time. A substantial benefit (e.g. a block of 50%) is attainable only during the first 3 to 4 hours.

For more prolonged iodine 131 exposure, iodide will be useful at any time during the exposure and hence should still be given even if the drug was not given shortly after the release of radioactivity.

Indications And Clinical Uses:

Prevention of thyroid uptake of radioiodine in a nuclear emergency situation.


Iodide sensitivity.

Warnings in Clinical States:

People allergic to iodide should not use Potassium iodide.

In case of overdose or allergic reaction, a physician should be contacted.

Adverse Reactions:

Thyrotoxicosis is unlikely to occur in iodine sufficient areas. Patients with nodular goiter have an increased risk of thyrotoxicosis if they receive large doses of iodides for several weeks or longer. Monitor at 4 week intervals if the treatment is prolonged.

Iodide goiter is rare after only a few weeks of iodide administration for limited periods of blocking.

Pregnancy: Respiratory obstruction of the infant by an enlarged thyroid should be looked for during delivery of women treated with iodide for any substantial period during pregnancy.

Patients with thyroiditis or other known parenchymal tissue damage or with low thyroid reserve for unknown reasons, should be watched for a propensity to suffer iodide myxedema.

Hypothyroidism with goiter is a rare complication of iodide ingestion. It is a distinct risk in patients who have been treated for thyrotoxicosis with radioiodine or surgery in the past or who have had Hashimoto’s thyroiditis and in addition received iodide for several weeks or longer.

Iodide parotitis is an uncommon complication, characterized by swelling of the salivary gland.

Cutaneous iodine occurs rarely in individuals who ingest large doses of iodine over long periods. It takes the appearance of a pustular acneform eruption.

Systemic manifestations rarely encountered; fever, generalized skin rash, arthralgia, inflammatory joint involvement and changes in the hair and nails. The appearance of these manifestations indicate that the iodine therapy should be discontinued.

Dosage And Administration:

Adults and children 1 year of age or older: 1 tablet once a day. Crush for small children.

Children under 1 year of age: 1/2 tablet once a day. Crush first.

To be taken for 10 days unless otherwise directed.

Availability And Storage:

Each white round flat tablet, one side bisected and the other side plain contains: potassium iodide 130 mg. Nonmedicinal ingredients: cellulose, magnesium stearate, silica gel and sodium thiosulfate. Gluten- and tartrazine-free. Special order only.

THYRO-BLOCK® Carter Horner Potassium Iodide Thyroid Blocking Agent

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