Usage
- Iodine is prescribed for the prevention and treatment of iodine deficiency and its consequences, including goiter and some thyroid disorders. A specific type, potassium iodide, is approved to prevent thyroid damage after radioactive iodine exposure. It is also used as an antiseptic and disinfectant for wound care.
- Pharmacological Classification: Trace element, antiseptic, expectorant (potassium iodide), thyroid-blocking agent (potassium iodide).
- Mechanism of Action: Iodine is essential for thyroid hormone synthesis. It is actively transported into thyroid follicular cells where it is oxidized and incorporated into tyrosine residues of thyroglobulin, forming thyroid hormones (T3 and T4). Potassium iodide competitively inhibits radioactive iodine uptake, reducing radiation-induced thyroid cancer risk. As an antiseptic, iodine exerts broad-spectrum antimicrobial activity by disrupting microbial protein synthesis and membrane integrity.
Alternate Names
- International/Regional variations: Iode (French), Iod (German), Iodio (Spanish), ヨウ素 (Japanese - Yōso)
- Brand Names: Many iodine supplements are available, often combined with other minerals. Potassium iodide is available as ThyroSafe, iOSAT, and Pima. Various antiseptic solutions containing povidone-iodine (Betadine is one example) are also marketed.
How It Works
- Pharmacodynamics: Iodine is crucial for thyroid hormone production, influencing metabolic rate, growth, and development. Potassium iodide blocks radioactive iodine uptake by the thyroid, protecting it from radiation damage. Topically, iodine acts as a broad-spectrum antiseptic, killing bacteria, fungi, viruses, and protozoa.
- Pharmacokinetics:
- Absorption: Iodine is readily absorbed from the gastrointestinal tract when taken orally. Topical absorption is minimal.
- Distribution: Iodine is distributed throughout the body, concentrating primarily in the thyroid gland. It also accumulates in salivary, gastric, and mammary glands.
- Metabolism: Iodine is oxidized in the thyroid to form thyroid hormones. Excess iodine is excreted primarily in the urine.
- Elimination: Renal excretion is the primary route of elimination for both iodine and potassium iodide.
- Mode of Action: In the thyroid, iodine is transported into follicular cells via the sodium-iodide symporter (NIS). It is then oxidized by thyroid peroxidase and incorporated into thyroglobulin. Coupling of iodotyrosines within thyroglobulin forms T3 and T4. Potassium iodide saturates the NIS, reducing radioactive iodine uptake. Antiseptic action involves disruption of microbial protein synthesis and cell membrane integrity.
Dosage
Standard Dosage
Adults:
- Iodine RDA: 150 mcg/day. Increased during pregnancy (220 mcg/day) and lactation (290 mcg/day).
- Potassium iodide for radiation protection: 130 mg once daily.
- Potassium iodide for hyperthyroidism: 1 mL three times a day.
Children:
- Iodine RDA varies with age. See specific guidelines below in FAQs.
- Potassium iodide dosing for radiation protection varies by age and is below.
Special Cases:
- Elderly Patients: Monitor thyroid function closely. Start with lower doses of iodine supplements and titrate as needed. May be more susceptible to iodine-induced hyperthyroidism.
- Patients with Renal Impairment: Dose adjustments of potassium iodide may be necessary. Monitor closely.
- Patients with Hepatic Dysfunction: Generally, no dosage adjustments are needed for iodine, but use potassium iodide with caution.
- Patients with Comorbid Conditions: Pre-existing thyroid disorders require careful monitoring and dose adjustment.
Clinical Use Cases:
The below dosages are for potassium iodide specifically:
- Intubation/Surgical Procedures/Mechanical Ventilation/ICU Use: Specific guidelines are not provided in the sources but pre-existing thyroid function must be considered.
- Emergency Situations (radiation exposure): Follow guidelines based on age categories as detailed in the FAQs.
Dosage Adjustments:
- Dose modifications for renal/hepatic dysfunction are needed for potassium iodide.
- Monitor thyroid function in patients with metabolic disorders or genetic polymorphisms affecting drug metabolism.
Side Effects
Common Side Effects:
- Iodine: Metallic taste, GI upset, acne-like rash.
- Potassium iodide: GI upset, rash, allergic reactions, and thyroid dysfunction can occur.
Rare but Serious Side Effects:
- Iodism: Metallic taste, burning mouth/throat, severe GI upset, and headache.
- Angioedema.
- Hyperthyroidism or hypothyroidism.
Long-Term Effects:
- Thyroid dysfunction with excessive iodine intake.
Contraindications:
- Hypersensitivity to iodine or potassium.
- Dermatitis herpetiformis.
- Hypocomplementemic vasculitis.
- Some thyroid disorders, such as Hashimoto’s thyroiditis or Graves’ disease.
Drug Interactions:
- Lithium: Increased risk of hypothyroidism.
- Antithyroid drugs: May interfere with thyroid hormone synthesis.
- Potassium-sparing diuretics: Risk of hyperkalemia with potassium iodide.
- ACE inhibitors: Risk of hyperkalemia with potassium iodide.
- Some medications (e.g., amiodarone) contain high levels of iodine, avoid additional iodine intake with these.
Pregnancy and Breastfeeding:
- Iodine is essential during pregnancy and breastfeeding. Supplementation is recommended for pregnant women and breastfeeding mothers (150 mcg/day). Consult a healthcare professional before increasing the dosage. Avoid kelp supplements due to variable iodine content and potential heavy metal contamination.
Drug Profile Summary
- Mechanism of Action: Essential for thyroid hormone synthesis; blocks radioactive iodine uptake (potassium iodide); antiseptic.
- Side Effects: Metallic taste, GI upset, rash, iodism (high doses), thyroid dysfunction.
- Contraindications: Iodine hypersensitivity, dermatitis herpetiformis, certain thyroid disorders.
- Drug Interactions: Lithium, antithyroid drugs, potassium-sparing diuretics, ACE inhibitors.
- Pregnancy & Breastfeeding: Essential, supplementation recommended (150 mcg/day), avoid kelp.
- Dosage: Varies by age and indication. See detailed sections above and FAQs below.
- Monitoring Parameters: Thyroid function tests (TSH, T3, T4), urinary iodine levels.
Popular Combinations:
- Iodine is often combined with other minerals in multivitamin/mineral supplements.
Precautions:
- Assess thyroid function before starting iodine supplementation.
- Monitor for signs of iodism or thyroid dysfunction.
- Avoid excessive iodine intake.
FAQs (Frequently Asked Questions)
Q1: What is the recommended dosage for Iodine?
A: The recommended daily allowance for iodine is 150 mcg for adults, 220 mcg for pregnant women, and 290 mcg for breastfeeding women. Children’s dosages vary by age and are further outlined in the FAQs.
Q2: What are the primary uses of Potassium Iodide?
A: Potassium iodide is primarily used to protect the thyroid gland from the effects of radioactive iodine exposure, to treat hyperthyroidism, and occasionally for iodine deficiency.
Q3: What are the symptoms of iodine deficiency?
A: Goiter (enlarged thyroid), hypothyroidism (fatigue, weight gain, constipation, dry skin), developmental delays in infants and children.
Q4: How is iodine deficiency diagnosed?
A: Urinary iodine concentration (UIC) is the most reliable indicator. A physical exam (checking for goiter) and thyroid function tests may also be performed.
Q5: Can iodine supplements be taken during pregnancy?
A: Yes, iodine supplementation is recommended during pregnancy (150 mcg/day). Adequate iodine intake is crucial for fetal brain development.
Q6: What is the appropriate dose of potassium iodide for radiation emergencies?
A: It is crucial to consult with authorities for current guidelines as to when to take potassium iodide. Dosage depends on age: Adults (up to 45 years): 130 mg (two tablets); Children 3-12 years: 65 mg (one tablet); Children 1 month-3 years: 32.5 mg (half a tablet); Infants under 1 month: 16.25 mg (quarter tablet). Those over 45 should not take potassium iodide for radiation protection. Pregnant and breastfeeding women (regardless of age) should take 130 mg.
Q7: What are the common side effects of potassium iodide?
A: Gastrointestinal upset, skin rash, and allergic reactions. Thyroid dysfunction can occur.
Q8: What should I do if I suspect iodine toxicity (Iodism)?
A: Discontinue iodine supplementation immediately and seek medical attention. Symptoms such as metallic taste, burning in the mouth and throat, GI upset, and headache require prompt management.
Q9: Are there any interactions between iodine and other medications?
A: Yes. Iodine can interact with lithium, antithyroid drugs, and potassium-sparing diuretics, among others. It’s important to inform your physician of all medications and supplements being taken before starting iodine supplementation.
Q10: Can iodine supplements be used to treat hyperthyroidism?
A: High doses of iodine (e.g., as potassium iodide solution - SSKI or Lugol’s solution) may be used short-term in conjunction with other medications to manage hyperthyroidism, particularly before surgery or radioactive iodine treatment. However, iodine alone is not typically a long-term solution for hyperthyroidism and can worsen the condition in some cases.
