Iodine (Potassium Iodide)

Potassium iodide participates in a complex series of reactions in the thyroid gland to produce thyroid hormones. When used for hyperthyroidism, it rapidly inhibits the release of thyroid hormones via a direct effect on the thyroid gland and inhibits the synthesis of thyroid hormones. Vascularity of the thyroid gland is reduced. In radiation emergencies, oral potassium iodide blocks thyroidal uptake of radioactive isotopes of iodine, minimizing the risk of radiation-induced thyroid neoplasms.

• Grave's disease
• Iodine deficiency disorders
• Hyperthyroidism
• Thyroid storm
• Preoperative reduction of vascularity of the thyroid gland
• Radiation protection against radioactive iodine
• Wound and ulcer cleansing

Adult Dose (Oral):

• Preoperative reduction of thyroid vascularity: 50-250 mg (approx 1-5 drops of solution containing 1 g/ml) tid for 10-14 days before surgery
• Radiation protection against radioactive iodine: 100-150 mg 24 hr before procedure and daily for up to 10 days after
• Thyrotoxicosis: 500 mg every 4 hr (given 1 hr after an antithyroid agent)
• Iodine deficiency disorders: Iodised oil: 400 mg iodine once yearly; Pregnant: 200 mg iodine as single dose

Child Dose (Oral):

• Preoperative reduction of thyroid vascularity: 50-250 mg tid for 10-14 days before surgery
• Radiation protection: Birth-1 month: 16 mg; 1 month-3 years: 32 mg; 3-18 years: 65 mg
• Iodine deficiency disorders: Up to 1 year: 100 mg; 1-5 years: 200 mg; >6 years: 400 mg

Side Effects:

• Hypersensitivity reactions (urticaria, angioedema, cutaneous haemorrhage, purpura, fever, arthralgia, lymphadenopathy, eosinophilia)
• Goitre
• Hypothyroidism
• Hyperthyroidism
• Iodism on prolonged use (metallic taste, increased salivation, swelling and inflammation of throat, swollen and irritated eyes, pulmonary oedema, nausea, vomiting, diarrhoea)

Potentially Fatal: Fatal periarteritis, ioderma

Precautions:

• Caution in pregnancy and lactation
• Caution in hyperkalaemia, hyperthyroidism, myotonia congenita, renal function impairment, tuberculosis, hypocomplementemic vasculitis, goiter, autoimmune thyroid disease
• Children: Repeated administration not recommended in neonates (risk of hypothyroidism)
• Caution in acute bronchitis

Contraindications:

• Hypersensitivity
• Acute bronchitis (potassium iodide)

Drug Interactions:

• Concurrent use with antithyroid agents may lead to additional hypothyroid effect
• Concurrent use with potassium-containing drugs or potassium-sparing diuretics may lead to hyperkalaemia
• Concurrent use with lithium salts may lead to additive hypothyroid effect (Potentially Fatal)

Use in Pregnancy: Caution in pregnancy; iodine deficiency disorders: pregnant patient 200 mg iodine as single dose (oral) or 480 mg iodine each year (IM).

Use in Lactation: Caution in lactation; iodine is excreted in breast milk; caution required for nursing mothers.

Pediatric Use: Dose provided above; repeated administration not recommended in neonates (risk of hypothyroidism).

Renal Impairment: Caution in renal function impairment; dose adjustment may be needed.

Hepatic Impairment: No specific data; consult your doctor.

Overdose: High doses may cause iodism (metallic taste, increased salivation, throat swelling, nausea, vomiting, diarrhoea), goitre, hypothyroidism, hyperthyroidism; provide symptomatic treatment.