Iobenguane I 123 and Amitriptyline: Interaction Details
AI-assisted, pharmacist-reviewed · AI content regenerated Jul 11, 2026 · Source data updated Jul 2, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Amitriptyline
Iobenguane I 123
No brand names on record
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.
Iobenguane I 123 is a special dye used for certain imaging scans. It works by traveling into nerve tissue using the same 'doorway' that your body uses for a natural chemical called norepinephrine. The scan can only show what it needs to if that dye gets picked up properly.
Amitriptyline (Elavil) blocks that doorway. If you take it around the time of your scan, the dye may not get taken up well, and the scan could look normal even when it isn't. That's called a false negative. The good news: this is easy to plan around. Your care team may have you pause the amitriptyline before the scan so the pictures come out accurate. Never stop it on your own, just talk with your doctor or pharmacist first.
Effect: Amitriptyline may cause false negative iobenguane I 123 imaging.
Mechanism: Iobenguane is a norepinephrine analog taken up via the norepinephrine transporter (NET) into adrenergic nerve terminals. Amitriptyline, a TCA, inhibits NET, reducing tracer uptake into target tissue and degrading image quality (a PD interaction on the tracer's distribution, not a metabolic one).
- Direction: Reduced diagnostic efficacy of iobenguane.
- Onset: Unspecified; relevant at time of imaging.
- Evidence: Theoretical, severity major.
- Management: Increasing iobenguane dose does NOT overcome the block. When clinically feasible, discontinue amitriptyline for at least 5 biological half-lives before imaging.
What happens
Potential for false negative imaging results
Interaction Deep Dive
Structurally, iobenguane resembles the neurotransmitter norepinephrine, and it enters adrenergic nerve terminals through the norepinephrine transporter, where it becomes stored within presynaptic storage vesicles. Because iobenguane concentrates in tissues that receive adrenergic innervation, tagging it with the isotope iodine 123 makes it possible to obtain images of particular organs and tissues. The clinical effectiveness of iobenguane I 123 may be compromised by antidepressants that block the function of the norepinephrine transporter, including SSRIs, tricyclic antidepressants, and MAOIs. Any inhibition of norepinephrine uptake caused by these agents cannot be counteracted by raising the dose of iobenguane I 123. When imaging with iobenguane I 123 is required, discontinue the interacting drug for a minimum of 5 biological half-lives if doing so is clinically feasible1.
Why it happens (mechanism)
Inhibition of norepinephrine transporter function by antidepressants
How to manage this interaction
This interaction is about scan accuracy, not day-to-day safety. Because amitriptyline can block the transporter the imaging dye needs, the scan could come back falsely normal.
- Keep taking your amitriptyline as prescribed unless your care team tells you otherwise.
- Tell the doctor ordering the scan and your pharmacist that you take amitriptyline, ideally well before the appointment.
- If the scan is needed, your team may have you pause amitriptyline for a set time (about 5 of its half-lives) so the pictures are reliable. They will plan this and monitor you.
- Do not stop the medicine on your own.
Management is individual — confirm any change with your pharmacist or prescriber.
Common questions
Can I take Iobenguane I 123 and Amitriptyline together?
Amitriptyline can cause a false negative iobenguane I 123 scan by blocking uptake of the imaging dye. Tell your care team you take it before scheduling the scan; they may pause it beforehand, but do not stop it on your own. Always confirm with your pharmacist or prescriber before making any change.
How serious is the Iobenguane I 123 and Amitriptyline interaction?
It is rated major. Potentially serious — often needs a change or close monitoring.
How quickly could this interaction happen?
The documented onset is "unspecified". The timing of this interaction is not well characterized.
How is the Iobenguane I 123 and Amitriptyline interaction managed?
This interaction is about scan accuracy, not day-to-day safety. Because amitriptyline can block the transporter the imaging dye needs, the scan could come back falsely normal. Keep taking your amitriptyline as prescribed unless your care team tells you otherwise. Tell the doctor ordering the scan and your pharmacist that you take amitriptyline, ideally well before the appointment. If the scan is n… Management is individual — always follow your own care team's guidance.
How strong is the evidence for this interaction?
The evidence is graded "theoretical". Predicted from the drugs' pharmacology; not yet confirmed in people.
From our Q&A
Real reader questions about these medications, each personally answered by our pharmacist:
Questions for your pharmacist
- Does my dose of Iobenguane I 123 or Amitriptyline 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: AdreView(TM) intravenous injection, iobenguane I 123 intravenous injection. GE Healthcare (per FDA), Arlington Heights, IL, 2013. DailyMed
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