Generic Name

Iodinated Serum Albumin I-131 (Megatope)

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Classification

FDA Approved Indications

• Assessment of plasma volume and blood volume measurement
• Evaluation of cardiac function and blood flow dynamics

Mechanism of Action

I-131 labeled albumin is injected into the bloodstream; its distribution and retention reflect blood volume and cardiac function, with gamma emissions detectable by imaging equipment.

Dosage and Administration

Adult: Administer according to specific diagnostic protocol, typically via intravenous injection, doses vary based on test requirements.

Pediatric: Use with caution; dosing guidelines depend on age and indication, consult pediatric protocols.

Geriatric: Adjust dose as needed based on renal and hepatic function, monitor closely due to potential comorbidities.

Renal Impairment: Use with caution; renal impairment may affect clearance of iodine and albumin, increasing radiation exposure.

Hepatic Impairment: Use cautiously; hepatic metabolism and clearance may alter biodistribution.

Pharmacokinetics

Absorption: Immediately available following intravenous injection.

Distribution: Distributed within the plasma; confined mainly to the vascular compartment.

Metabolism: Metabolized or cleared via renal pathways; radioactive iodine is released and can be taken up by the thyroid gland.

Excretion: Primarily through renal excretion of free iodine; residual albumin cleared via reticuloendothelial system.

Half Life: I-131 has a physical half-life of approximately 8 days.

Contraindications

• Known hypersensitivity to albumin or iodine-containing compounds.
• Pregnancy and lactation—use only if benefits outweigh risks.

Precautions

• Use caution in patients with thyroid disease, radioactive iodine sensitivity, or recent radioiodine therapy.
• Ensure proper shielding and procedures in handling radioactive materials.

Adverse Reactions - Common

• Allergic reactions such as rash, hives (Rare)
• Injection site reactions (Less common)

Adverse Reactions - Serious

• Anaphylaxis (Very rare)
• Thyroid gland uptake leading to hyperthyroidism or hypothyroidism (Rare)

Drug-Drug Interactions

• Other radioactive iodine preparations, which may alter uptake or increase radiation dose.

Drug-Food Interactions

• Limit iodine-rich foods prior to test to improve accuracy.

Drug-Herb Interactions

• No specific herb interactions documented.

Nursing Implications

Patient/Family Teaching

• Explain the purpose of the test and radioactive precautions.
• Advise avoiding contact with pregnant women and young children for a period post-procedure.
• Report any symptoms of allergic reaction immediately.

Special Considerations

Black Box Warnings:

• Use with caution due to radiation exposure; minimize exposure to staff and family.
• Thyroid uptake of radioactive iodine can cause harm, especially in children and pregnant women.

Genetic Factors: Patients with prior thyroid disease or genetic predisposition should be evaluated carefully.

Lab Test Interference: Radioactive iodine may interfere with thyroid function tests and other iodine-based imaging or tests.

Overdose Management

Signs/Symptoms: Signs include radiation sickness, hypothyroidism or hyperthyroidism symptoms, allergic reactions.

Treatment: Supportive care, symptom management, and potentially administration of iodine to block thyroid uptake if overdose suspected.

Storage and Handling

Storage: Store in a secure, shielded, lead-lined container, at controlled room temperature.

Stability: Stable under proper storage; avoid extreme temperatures and light.