iodine, iodide

Rapidly inhibits the release and synthesis of thyroid hormones.
Decreases the vascularity of the thyroid gland.
Decreases thyroidal uptake of radioactive iodine following radiation emergencies or administration of radioactive isotopes of iodine.
Iodine is a necessary component of thyroid hormone.

Therapeutic effects:

Control of hyperthyroidism.
Decreased bleeding during thyroid surgery.
Decreased incidence of thyroid cancer following radiation emergencies.

Pharmacokinetics ⬆ ⬇

Absorption: Converted in the GI tract and enters the circulation as iodine; also absorbed through skin and lungs; may also be obtained via recycling of iodothyronines.

Distribution: Concentrates in the thyroid gland and muscle; also found in skin, skeleton, breasts, and hair. Readily crosses the placenta; enters breast milk.

Metabolism/Excretion: Taken up by the thyroid gland, then eliminated via kidneys, liver, skin, lungs, and intestines.

Half-Life: Unknown.

Time/Action Profile ⬆ ⬇

(effects on thyroid)

ROUTE	ONSET	PEAK	DURATION
PO	24 hr	10–15 days	variable‡

‡Radiation protection lasts 24 hr.

Contraind./Precautions ⬆ ⬇

Contraindicated in:

Hypersensitivity;
Hyperkalemia;
Pulmonary edema;
Impaired renal function.

Use Cautiously in:

Tuberculosis;
Bronchitis;
Cardiovascular disease;
OB: Pregnancy or lactation (although iodine is required during pregnancy, excess amounts may cause thyroid abnormalities/goiter in the newborn; excess use during lactation may cause skin rash or thyroid suppression in the infant).

Adv. Reactions/Side Effects ⬆ ⬇

GI: GI BLEEDING, diarrhea, nausea, vomiting

Derm: acneiform eruptions

Endo: hypothyroidism, goiter, hyperthyroidism

F and E: hyperkalemia

Neuro: tingling, confusion, weakness

MS: joint pain

Misc: hypersensitivity, iodism

Interactions ⬆ ⬇

Drug-drug:

Use with lithium may cause ↑ hypothyroidism.
↑antithyroid effect of methimazole and propylthiouracil.
↑hyperkalemia may result from combined use with potassium-sparing diuretics, ACE inhibitors, angiotensin II receptor antagonists or potassium supplements.

Route/Dosage ⬆ ⬇

Preparation for Thyroidectomy

Hyperthyroidism

Radiation Protectant to Radioactive Isotopes of Iodine

Reduction of Thyroid Cancer after Nuclear Accident

PO (Adults and Children ): Strong iodine solution—3–5 drops (0.1–0.3 mL) 3 times daily for 10 days prior to surgery. Potassium iodide saturated solution (SSKI)—1–5 drops (50–250 mg) 3 times daily for 10 days prior to surgery.
PO (Adults and Children ): Strong iodine solution—1 mL in water 3 times daily. Potassium iodide saturated solution (SSKI)—6–10 drops (300–500 mg) 3 times daily.
PO (Infants <1 yr): 3–5 drops (150–250 mg) 3 times daily.
PO (Adults ): Pima—195 mg once daily for 10 days (start 24 hr prior to exposure (continue until risk of exposure has passed or other measures have been implemented).
PO (Children >1 yr): 130 mg once daily for 10 days (start 24 hr prior to exposure).
PO (Infants <1 yr): 65 mg once daily for 10 days (start 24 hr prior to exposure).
PO (Adults and Children >68 kg, including pregnant/lactating women): Iosat, ThyroSafe, ThyroShield—130 mg once daily (continue until risk of exposure has passed or other measures have been implemented).
PO (Children 3–18 yr): 65 mg once daily.
PO (Children 1 mo–3 yr): 32.5 mg once daily.
PO (Infants <1 mo): 16.25 mg once daily.

Availability ⬆ ⬇

Potassium Iodide

Strong Iodine Solution

Oral solution: 65 mg/mL (ThyroShield); 1 g potassium iodide/mL (SSKI)
Syrup (Pima) black-raspberry flavor: 325 mg potassium iodide/5 mL
Tablets: 65 mgOTC; 130 mgOTC(available only through state and federal agencies)
Oral solution: Iodine 50 mg/mL plus potassium iodide 100 mg/mL

Assessment ⬆ ⬇

Assess for signs and symptoms of iodism (metallic taste, stomatitis, skin lesions, cold symptoms, severe GI upset). Report these symptoms promptly.
Monitor response symptoms of hyperthyroidism (tachycardia, palpitations, nervousness, insomnia, diaphoresis, heat intolerance, tremors, weight loss).
Monitor for hypersensitivity reaction (rash, pruritus, laryngeal edema, wheezing). Discontinue drug and notify physician immediately if these problems occur.

Lab Test Considerations:

Monitor thyroid function before and periodically during therapy. May alter results of radionuclide thyroid imaging and may ↓ thyroidal uptake of ¹³¹I, ¹²³I, and sodium pertechnetate ^99mTc in thyroid uptake tests.
- Monitor serum potassium levels periodically during therapy.
Monitor thyroid stimulating hormone (TSH) and free T₄ in neonates (within the first mo of life) treated with potassium iodide for development of hypothyroidism. Thyroid hormone therapy should be instituted if hypothyroidism develops.

Implementation ⬆ ⬇

Do not confuse iodine with Lodine (etodolac).
- For protection against inhaled radioiodines, administer potassium iodide prior to or immediately coincident with passage of the radioactive cloud, though a substantial protective effect lasts 3–4 hr after exposure.
PO: Mix solutions in a full glass of fruit juice, water, broth, formula, or milk. Administer after meals to minimize GI irritation.
- Solution is normally clear and colorless. Darkening upon standing does not affect potency of drug. Solutions that are brownish yellow should be discarded.
- Crystals may form, especially if refrigerated, but redissolve upon warming and shaking.

Patient/Family Teaching ⬆ ⬇

Instruct patient to take medication as directed. Take missed doses as soon as possible but not just before next dose; do not double doses.
Instruct patient to report suspected pregnancy to health care professional before therapy is initiated.
Advise patient to consult health care professional about avoiding foods high in iodine (seafood, iodized salt, cabbage, kale, turnips) or potassium (see Food Sources for Specific Nutrients).
Advise patient to consult health care professional before using OTC or herbal cold remedies. Some cold remedies use iodide as an expectorant.
Hyperthyroidism: Instruct patient to take medication as ordered. Missing a dose may precipitate hyperthyroidism.

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Classifications ⬇

Indications ⬆ ⬇

Action ⬆ ⬇