Drug Guide
Sodium Iodide I-131
Classification
Therapeutic: Radioactive iodine therapy for thyroid conditions
Pharmacological: Radioisotope
FDA Approved Indications
- Treatment of hyperthyroidism (Graves' disease, toxic multinodular goiter)
- Remnant ablation in differentiated thyroid cancer
Mechanism of Action
I-131 emits beta particles destroying thyroid tissue through localized radiation, reducing thyroid hormone production or ablated residual thyroid tissue after surgery.
Dosage and Administration
Adult: Dose varies based on condition; typically 185-370 MBq (5-10 mCi) for hyperthyroidism, and tailored for thyroid cancer ablation.
Pediatric: Dosing based on body weight or surface area; closely monitored by specialist.
Geriatric: Use with caution; adjust dose based on patient health and response.
Renal Impairment: Use caution; dose adjustments may be necessary.
Hepatic Impairment: No specific adjustments typically necessary.
Pharmacokinetics
Absorption: Rapid absorption after oral administration.
Distribution: Selectively taken up by functional thyroid tissue.
Metabolism: Not metabolized; acts directly as a radioisotope.
Excretion: Primarily excreted via urine, within 48-72 hours.
Half Life: Approximately 8 days (I-131 physical half-life).
Contraindications
- Pregnancy (category X), breastfeeding
- Known hypersensitivity to iodine or I-131
Precautions
- Use in caution with patients with radiation sickness, or recent exposure to high doses of radiation.
- Limit exposure to others to prevent radiation contamination.
Adverse Reactions - Common
- Neck pain or swelling (Common)
- Radiation thyroiditis (Common)
Adverse Reactions - Serious
- Radiation sickness symptoms (nausea, vomiting, fatigue) (Serious but rare)
- Secondary malignancies (very rare) (Very rare)
Drug-Drug Interactions
- Amiodarone (can affect thyroid function)
Drug-Food Interactions
- Limit iodine-rich foods before treatment as instructed by provider.
Drug-Herb Interactions
N/ANursing Implications
Assessment: Assess thyroid function tests, patient history of radiation exposure.
Diagnoses:
- Risk for radiation injury related to radioactive iodine therapy.
Implementation: Administer as prescribed, enforce radiation safety precautions, educate patient about radiation exposure.
Evaluation: Monitor thyroid function, assess for side effects, ensure radiation safety.
Patient/Family Teaching
- Follow all instructions regarding radiation safety.
- Limit contact with others for specified period.
- Report any symptoms of hypothyroidism or radiation sickness.
Special Considerations
Black Box Warnings:
- Use only under specialized medical supervision due to radiation hazards.
Genetic Factors: Radioactive iodine therapy may have implications for future offspring—discuss with healthcare provider.
Lab Test Interference: Can affect thyroid function tests; interpret with caution within the context of recent therapy.
Overdose Management
Signs/Symptoms: Radiation poisoning symptoms, increased radiation exposure symptoms.
Treatment: Supportive care, symptomatic treatment, and decontamination if indicated.
Storage and Handling
Storage: Store in lead-shielded container at appropriate radiation safety standards.
Stability: Stable under recommended storage conditions.