Methimazole and Amiodarone: Interaction Details
AI-assisted, pharmacist-reviewed · Source data updated Aug 8, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Amiodarone
Methimazole
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
Decreased T4/T3
Interaction Deep Dive
Combination therapy with methimazole and amiodarone induced a greater fall in serum triiodothyronine (T3) and thyroxine (T4) than methimazole alone in newly diagnosed hyperthyroid patients1.
Why it happens (mechanism)
Increased iodide release
Literature reports
1 report — tap to read
a) Ten hyperthyroid patients were treated with amiodarone and methimazole, or with placebo and methimazole for 10 days. Thyroid hormone levels were measured in both groups: in the hyperthyroid patients treated with both drugs, both T3 and T4 declined more significantly than when methimazole was used with a placebo 1.
Common questions
Can I take Methimazole and Amiodarone together?
Decreased T4/T3 Always confirm with your pharmacist or prescriber before making any change.
How serious is the Methimazole and Amiodarone interaction?
It is rated minor. Usually limited clinical impact.
How quickly could this interaction happen?
The documented onset is "delayed". Effects tend to build up gradually over days to weeks.
How strong is the evidence for this interaction?
The evidence is graded "probable". Good supporting evidence, though not definitively proven.
From our Q&A
Real reader questions about these medications, each personally answered by our pharmacist:
Questions for your pharmacist
- Does my dose of Methimazole or Amiodarone 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 anything you'd monitor while I'm on both?
References (1)
- Van Reeth O, Decoster C, Unger J, et al: Effect of amiodarone on serum T4 and T3 levels in hyperthyroid patients treated with methimazole. Eur J Clin Pharmacol 1987; 32:223-227. DOI
Keep reading about Amiodarone
Keep reading about Methimazole
These medications also interact with supplements
Prescription drugs aren't the whole picture — herbal and dietary supplements can interact with them too. From the evidence-graded Natural Medicines database:
major · moderate · minor — check everything you take with our drug–supplement interaction checker.
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