Iodopol (Sodium Iodide (131i))

Iodopol is used in thyroid‑related conditions where radioactive iodine uptake is desired.

• Thyroid cancer (post‑surgical ablation): eliminates residual thyroid tissue to reduce recurrence risk.
• Hyperthyroidism: decreases hormone production by destroying overactive thyroid cells.
• Pre‑surgical thyroid tissue ablation: reduces gland size and vascularity before definitive surgery.

• Sodium Iodide (I‑131) is taken up by the sodium‑iodide symporter in thyroid follicular cells. Once inside the gland, the radioactive isotope emits beta particles that cause localized cytotoxicity, leading to cellular apoptosis and necrosis. The short tissue penetration limits damage to adjacent structures, while the gamma emissions allow imaging of iodine distribution. This selective uptake enables targeted ablation of thyroid tissue.

Iodopol may cause a range of adverse reactions, varying from mild to severe.

Common Side Effects

• Nausea: mild gastrointestinal upset occurring shortly after ingestion.
• Salivary gland swelling: transient enlargement causing discomfort.
• Taste alteration: metallic or altered taste perception lasting days.
• Fatigue: temporary reduction in energy levels.
• Dry mouth: reduced salivary flow and mild throat irritation.

Serious or Rare Side Effects

• Severe hypothyroidism: profound reduction in thyroid hormone requiring replacement.
• Radiation thyroiditis: painful inflammation of the thyroid gland.
• Bone marrow suppression: decreased blood cell counts leading to infection risk.
• Secondary malignancy: rare risk of radiation‑induced cancers developing years later.

When using Iodopol, several precautions should be observed to ensure patient safety and product integrity.

• Pregnancy: avoid use unless benefits outweigh potential risks, as fetal effects are unknown.
• Breastfeeding: discontinue breastfeeding or consider alternative therapy due to possible iodine transfer.
• Renal impairment: assess kidney function and adjust monitoring, as excretion is renal.
• Thyroid function: evaluate baseline thyroid status and monitor hormone levels after administration.
• Iodine allergy: contraindicated in patients with known hypersensitivity to iodine compounds.
• Store below 25°C: keep in the original container, protect from moisture and light.

Iodopol can interact with other medicines; awareness of major and moderate interactions helps prevent adverse outcomes.

Major Interactions (Avoid)

• Lithium: concurrent use may exacerbate lithium toxicity.
• Antithyroid drugs (e.g., methimazole, propylthiouracil): reduce efficacy of radioactive iodine.
• Amiodarone: high iodine content interferes with iodine uptake and thyroid function.
• Thyroid hormone replacement therapy: may require dose adjustment after ablation.
• Radioactive contrast agents: can block iodine uptake if administered shortly before or after Iodopol.

Moderate Interactions (Monitor Closely)

• ACE inhibitors: may alter renal clearance of iodine.
• Diuretics: affect potassium balance influencing thyroid uptake.
• Calcium supplements: can reduce oral absorption of iodine if taken simultaneously.
• Beta‑blockers: monitor heart rate as thyroid hormone changes affect cardiovascular response.
• Corticosteroids: may modify inflammatory response after iodine therapy.