Iobenguane I 131 and Guanabenz: Interaction Details
AI-assisted, pharmacist-reviewed · Source data updated Aug 8, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Guanabenz
Iobenguane I 131
How we grade severity & evidence
Severity levels
- Contraindicated: These should generally not be used together.
- Major: Potentially serious — often needs a change or close monitoring.
- Moderate: Can be significant — usually manageable with monitoring.
- Minor: Usually limited clinical impact.
Evidence grades
- Established: Well documented — supported by controlled studies or strong clinical data.
- Probable: Good supporting evidence, though not definitively proven.
- Suspected: Some evidence suggests this interaction, but it is not well established.
- Possible: Limited or conflicting evidence; the interaction may occur.
- Theoretical: Predicted from the drugs' pharmacology; not yet confirmed in people.
Ratings come from the documented interaction literature and are reviewed by a pharmacist. They describe the documented risk of the combination, not what will necessarily happen to you — your dose, timing, and health picture all matter.
What happens
Inaccurate dosimetry calculations or reduced efficacy
Interaction Deep Dive
Drugs that reduce catecholamine uptake or deplete catecholamine stores, including alpha agonists or alpha/beta agonists, may interfere with iobenguane uptake into cells and therefore interfere with dosimetry calculations or the efficacy of iobenguane I-131. Discontinue such drugs for at least 5 half-lives before administration of either the dosimetry or a therapeutic dose of iobenguane I-131 and then wait for at least 7 days after each iobenguane I-131 dose before restarting the interfering agent(s)1.
Why it happens (mechanism)
Interference with iobenguane uptake into cells
Common questions
Can I take Iobenguane I 131 and Guanabenz together?
Inaccurate dosimetry calculations or reduced efficacy Always confirm with your pharmacist or prescriber before making any change.
How serious is the Iobenguane I 131 and Guanabenz interaction?
It is rated major. Potentially serious — often needs a change or close monitoring.
How quickly could this interaction happen?
The documented onset is "rapid". Effects can appear quickly, often within about 24 hours of combining the drugs.
How strong is the evidence for this interaction?
The evidence is graded "theoretical". Predicted from the drugs' pharmacology; not yet confirmed in people.
Questions for your pharmacist
- Does my dose of Iobenguane I 131 or Guanabenz need adjusting while I take them together?
- What symptoms should prompt me to call you or my prescriber right away?
- Does the timing of my doses matter for this combination?
- Is there a safer alternative to one of these medications for me?
References (1)
- Product Information: AZEDRA(R) intravenous injection, iobenguane I 131 intravenous injection. Progenics Pharmaceuticals Inc (per FDA), New York, NY, 2018.
Keep reading about Iobenguane I 131
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