IOBENGUANE I-123
Clinical safety rating: caution
Comprehensive clinical and safety monograph for IOBENGUANE I-123 (IOBENGUANE I-123).
Iobenguane I-123 is a radiopharmaceutical analog of norepinephrine that is taken up by adrenergic neurons and neuroendocrine tumors via the norepinephrine transporter (NET). It localizes in tissues rich in sympathetic innervation and tumors expressing NET, enabling scintigraphic imaging.
| Metabolism | Iobenguane I-123 is not metabolized; it undergoes renal excretion as unchanged drug. The iodine-123 label decays by electron capture with a half-life of 13.2 hours, emitting gamma radiation. |
| Excretion | Renal: 40-60% as unchanged iobenguane within 24 hours; biliary/fecal: minimal (<5%) |
| Half-life | Terminal elimination half-life: 5-7 hours; clinically relevant for imaging timing (optimal scanning at 24 hours post-injection) |
| Protein binding | Less than 1% bound; negligible binding to plasma proteins |
| Volume of Distribution | Vd: approximately 10-15 L/kg; indicates extensive tissue binding, especially to adrenergic-rich organs |
| Bioavailability | IV only: 100% bioavailability; not administered orally due to first-pass metabolism and low oral absorption |
| Onset of Action | IV: immediate uptake by adrenergic tissues; imaging visualization begins at 1 hour post-injection |
| Duration of Action | Duration of imaging window: up to 48 hours; peak tumor-to-background ratio at 24 hours |
Intravenous administration of 5 mCi (185 MBq) as a single dose for imaging.
| Dosage form | SOLUTION |
| Renal impairment | No dose adjustment required for renal impairment; GFR does not affect dosing. |
| Liver impairment | No specific guidelines for Child-Pugh modifications; use caution in severe hepatic impairment. |
| Pediatric use | 0.14 mCi/kg (5.18 MBq/kg) intravenously, minimum dose 0.5 mCi (18.5 MBq), maximum dose 5 mCi (185 MBq). |
| Geriatric use | No specific dose adjustment; use lowest effective dose due to potential renal and hepatic decline. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for IOBENGUANE I-123 (IOBENGUANE I-123).
| Breastfeeding | Iobenguane I-123 is excreted in human milk. The M/P ratio is not established. Due to radioactivity, breastfeeding should be discontinued for at least 48 hours after administration. Pump and discard milk during this period. |
| Teratogenic Risk | Iobenguane I-123 is a radioactive diagnostic agent. Radiation exposure from diagnostic doses is generally below the threshold for teratogenesis, but theoretical risks exist. First trimester: Avoid unless benefit justifies risk; consider alternative non-radiating modalities. Second and third trimesters: Fetal risk is low with standard doses; however, cumulative radiation dose should be minimized. Use only if clearly needed. |
■ FDA Black Box Warning
None.
| Serious Effects |
["Known hypersensitivity to iobenguane or any component of the formulation"]
| Precautions | ["Risk of radiation exposure; use only when diagnostic yield justifies dose","Potential for false-negative results in patients taking drugs that inhibit norepinephrine transporter (e.g., tricyclic antidepressants, sympathomimetics)","Hydrate patient before administration to reduce bladder radiation dose","Use in pregnancy only if potential benefit justifies risk to fetus","Caution in patients with impaired renal function due to altered clearance"] |
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| Fetal Monitoring | Maternal: Monitor for hypersensitivity reactions (rare). Fetal: No specific monitoring required for diagnostic use. Cumulative radiation dose to fetus should be calculated and kept as low as reasonably achievable. |
| Fertility Effects | No known adverse effects on fertility from diagnostic doses. High doses (therapeutic) may cause gonadal damage; not applicable for I-123 diagnostic use. |