Nátrium-Jodid [131i] Curium Netherlands B.V. (Sodium Iodide (131i))

Nátrium-Jodid [131i] is a diagnostic radiopharmaceutical used in nuclear medicine imaging of the thyroid and related disorders.

• Thyroid scintigraphy: Enables visualization of functional thyroid tissue and helps differentiate benign from malignant nodules.
• Radioiodine uptake test: Quantifies iodine absorption by the thyroid gland to guide treatment decisions.
• Whole‑body scan for metastatic thyroid cancer: Detects iodine‑avid metastatic lesions throughout the body.
• Assessment of ectopic thyroid tissue: Identifies ectopic or residual thyroid tissue after surgery.
• Evaluation of thyroiditis: Assists in distinguishing inflammatory thyroid conditions from other causes of dysfunction.

• Sodium Iodide (131I) is a radioactive isotope that emits beta particles and gamma photons. After intravenous administration, it is actively transported into thyroid follicular cells via the sodium‑iodide symporter. The emitted radiation provides imaging contrast, allowing gamma cameras to map iodine uptake and assess functional activity of thyroid tissue and iodine‑avid lesions.

Adverse reactions to sodium iodide (131I) are generally related to its radioactivity and the intravenous route.

Common Side Effects

• Nausea: Mild to moderate nausea may occur shortly after injection.
• Metallic taste: A transient metallic sensation in the mouth is reported by some patients.
• Local irritation: Mild pain or erythema at the injection site.
• Headache: Occasional mild headache following administration.
• Fatigue: Temporary feeling of tiredness after the procedure.

Serious or Rare Side Effects

• Radiation‑induced thyroiditis: Inflammation of the thyroid gland due to radiation exposure.
• Allergic reaction: Hives, itching, or anaphylaxis in rare cases.
• Bone marrow suppression: Very rare, may present as decreased blood cell counts.
• Severe nausea or vomiting: Persistent gastrointestinal upset requiring medical attention.
• Pulmonary fibrosis: Extremely rare lung tissue reaction to radiation.

When using sodium iodide (131I), clinicians should consider several safety measures.

• Pregnancy testing: Confirm non‑pregnant status before administration due to fetal radiation risk.
• Breastfeeding restriction: Advise cessation of breastfeeding for a period defined by local guidelines.
• Thyroid function assessment: Verify baseline thyroid status to interpret imaging results accurately.
• Radiation safety: Follow institutional protocols for handling radioactive materials and protect staff and family members.
• Patient counseling: Inform patients about possible transient symptoms and post‑procedure precautions.
• Store at ambient temperature: Keep in original container, protect from light and moisture, and handle in compliance with radiopharmacy guidelines.

Sodium iodide (131I) may interact with other substances that affect iodine metabolism or radiation exposure.

Major Interactions (Avoid)

• Antithyroid drugs (e.g., methimazole, propylthiouracil): May reduce uptake of the radiotracer, compromising diagnostic accuracy.
• High‑dose potassium iodide: Competes for the sodium‑iodide symporter and can block tracer uptake.

Moderate Interactions (Monitor Closely)

• Lithium: Can alter thyroid iodine handling and affect scan results.
• Amiodarone: Contains iodine and may interfere with tracer distribution.
• Radioactive contrast agents: May increase overall radiation burden if administered close in time.
• Corticosteroids: May modify inflammatory response and affect interpretation of thyroiditis imaging.
• Diuretics: May influence renal clearance of the radiotracer, altering background activity.