sodium iodide I 123: clinical use

Prescribing considerations

• Use only when diagnostic benefit justifies radiation exposure, keeping exposure as low as reasonably achievable.
• Review pregnancy and breastfeeding status, iodine exposure, medicines, supplements and recent contrast procedures.
• Consider increased radiation exposure in significant renal or hepatic impairment.
• In children and adolescents, justify the indication carefully because effective radiation exposure is greater than in adults.

Contraindications and cautions

• Hypersensitivity to sodium iodide I 123 or any formulation excipient.
• Use additional caution where pregnancy is possible, during breastfeeding, and in significant renal or hepatic impairment.

Monitoring

• Confirm identity, indication, pregnancy status and preparation before administration.
• Observe for hypersensitivity and ensure resuscitation medicines and equipment are available.
• Support hydration and frequent voiding after administration.
• Assess image and uptake quality in the context of medicines, iodine exposure and thyroid function.

Clinical pharmacology

Intravenous iodide is concentrated by thyroid tissue. Iodine-123 has a physical half-life of approximately 13 hours and emits gamma radiation suitable for external detection; unabsorbed iodide is eliminated mainly in urine.

Formulation and product differences

• The selected product is a ready-to-use, clear, colourless solution for intravenous injection in a shielded multidose vial.
• It contains sodium thiosulphate, sodium bicarbonate, sodium chloride, acetic acid, sodium hydroxide and water for injections, and is considered essentially sodium-free per administration.
• It must not be mixed with other medicinal products because compatibility studies are unavailable.
• Longer-lived radioiodine contaminants may influence dosimetry and breastfeeding precautions.