Potassium iodide

Potassium iodide is an active ingredient with thyroid-protective and expectorant properties. It is administered in oral tablet form during a nuclear radiation emergency to prevent the absorption of radioactive iodine. This protects the thyroid gland from carcinogenic radiation. In some European countries, potassium iodide tablets are stocked, for example, in schools and childcare facilities (Austria), obtained free of charge from pharmacies (Germany), or distributed to communities in the vicinity of nuclear facilities (Switzerland). In most cases, the population is asked to take it by radio.

As an adjunct to other thyroid function-inhibiting drugs, potassium iodide can also be used in the treatment of hyperthyroidism, e.g., preoperatively to induce thyroid regression.

Pharmacodynamics

Potassium iodide blocks the formation and release of thyroid hormones, reducing the visibility of blood vessels on the body. Thyroid tissue solidifies, thyroid cells shrink, protein-bound inactivated thyroxine (thyroid hormone) reaccumulates, and the level of bound iodine increases.
Zum Schutz während einer Strahlenexposition wird durch Kaliumiodid die Aufnahme radioaktiver Iodisotope durch die Schilddrüse gehemmt und das Risiko von strahleninduzierte Schilddrüsentumoren minimiert.
Die höchste Schutzwirkung wird erreicht, wenn die Einnahme kurz vor bzw. gleich zu Beginn der radioaktiven Exposition erfolgt. Eine Verabreichung nach wenigen Stunden senkt die Effizienz des Wirkstoffes bereits um 15% bzw. 50 %. Somit ist eine verspätete Einnahme kaum noch wirksam.

Pharmacokinetics

Orally ingested potassium iodide is virtually completely absorbed in the small intestine. Prior to absorption, iodine and iodate are reduced to iodide in the intestine. The retained iodide is stored in the thyroid gland, salivary glands, mammary glands and stomach. The iodide circulating in the blood is almost completely excreted by the kidneys within a day, but can also be found in tears, sweat and milk.

Drug interactions

Simultaneous use of lithium promotes enlargement of the thyroid gland (goiter) and development of hypothyroidism. Increased blood potassium concentrations may occur while taking potassium-sparing diuretic (diuretic) medications. The effects of drugs used to treat hyperthyroidism (methimazole, propylthiouracil) may be attenuated by potassium iodide.

Contraindications

Because some individuals are markedly sensitive to iodine, potassium iodide should be used with caution during initial administration. Patients at risk for iodine-induced side effects include those with hypocomplementemic vasculitis (chronic vasculitis), thyroid swelling, or autoimmune thyroid disease.
Während der Schwangerschaft kann die Einnahme von Kaliumiodid Probleme der Schilddrüse bei Mutter und Kind bewirken, wobei die Schutzwirkung vor radioaktiver Strahlung (im Fall einer Exposition) das Risiko einer Schädigung der Schilddrüse überwiegt.
Bei Patienten mit Tuberkulose sollte Kaliumiodid nur mit äußerster Vorsicht angewendet werden, genauso wie bei einer Autoimmunerkrankung der Schilddrüse, da Iod stimulierend auf die Autoimmunität der Schilddrüse wirkt.

Side effects

The risk of side effects increases with age.
Zu den unerwünschten Nebenwirkungen gehören:

• Digestive problems
• metallic taste
• Conjunctivitis
• swelling of the salivary glands
• Headache
• Cough
• Bronchitis
• pulmonary edema
• palpitations
• Restlessness

In rare cases, hyperthyroidism or hypothyroidism and hypersensitivity reactions occur.

Toxicological data

LD50 (rats, intravenous): 285 mg/kg