Natrii Iodidum (131i) Polatom (Sodium Iodide (131i))

Natrii Iodidum (131i) Polatom is a radioactive iodine agent used in the management of thyroid‑related disorders and imaging.

• Hyperthyroidism: reduces excess thyroid hormone production by selectively destroying overactive thyroid cells.
• Thyroid cancer: eliminates residual thyroid tissue after surgery to lower recurrence risk.
• Thyroid tissue ablation: prepares patients for subsequent radioiodine therapy by ablating remaining thyroid tissue.
• Diagnostic thyroid imaging: provides functional imaging to assess thyroid uptake and distribution.

• Sodium Iodide (I-131) is actively taken up by thyroid follicular cells via the sodium‑iodide symporter. Once inside the gland, the beta particles emitted by I‑131 cause localized radiation injury, leading to selective destruction of thyroid tissue while sparing surrounding structures. This targeted cytotoxic effect underlies both therapeutic ablation and diagnostic imaging applications.

Adverse reactions may occur following oral administration of I‑131 radiopharmaceuticals.

Common Side Effects

• Nausea or vomiting
• Transient neck discomfort or soreness
• Mild hypothyroidism during the first weeks
• Altered taste sensation
• Temporary leukopenia or mild bone‑marrow suppression
• Mild salivary gland irritation

Serious or Rare Side Effects

• Severe or prolonged hypothyroidism requiring hormone replacement
• Acute radiation thyroiditis with significant pain and swelling
• Bone‑marrow failure leading to pancytopenia
• Allergic or hypersensitivity reactions, including rash or anaphylaxis
• Pulmonary fibrosis (rare) from systemic radiation exposure
• Secondary malignancies due to radiation exposure (very rare)

Careful assessment and monitoring are required when using I‑131 radiopharmaceuticals.

• Pregnancy: avoid use unless the benefit outweighs the risk to the fetus.
• Breastfeeding: discontinue treatment and advise cessation of nursing until radioactivity is cleared.
• Renal impairment: monitor renal function and adjust timing of administration as needed.
• Concomitant thyroid hormone therapy: closely monitor thyroid hormone levels and adjust dosage.
• Radiation safety: implement measures to limit exposure to family members and healthcare staff.
• Store at ambient temperature: keep in original packaging, protect from moisture and light, and store below 25 °C.

I‑131 may interact with other medications that affect thyroid function or radiation response.

Major Interactions (Avoid)

• Antithyroid drugs (e.g., propylthiouracil, methimazole) can reduce iodine uptake.
• Lithium therapy may alter thyroid hormone dynamics and increase risk of hypothyroidism.
• High‑dose iodine supplements or contrast agents can competitively inhibit I‑131 uptake.
• Radioprotective agents such as amifostine may diminish therapeutic efficacy.
• Concurrent chemotherapy causing bone‑marrow suppression may exacerbate hematologic toxicity.

Moderate Interactions (Monitor Closely)

• Levothyroxine replacement: adjust dose based on thyroid function tests.
• Corticosteroids: may mask inflammatory responses.
• Anticoagulants: monitor for bleeding if thyroiditis occurs.
• Diuretics: watch for electrolyte disturbances during thyroid inflammation.
• Antihistamines: may affect perception of mild allergic reactions.