Amiodarone and Letermovir Injection: Interaction Details
AI-assisted, pharmacist-reviewed · Source data updated Aug 8, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Amiodarone
Letermovir Injection
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
Increased amiodarone exposure
Interaction Deep Dive
Amiodarone is a CYP3A substrate. Avoid coadministration of amiodarone with a CYP3A inhibitor, such as letermovir, as increased exposure to amiodarone may occur2. If concomitant use is necessary, frequently monitor amiodarone concentrations and watch for signs of amiodarone-related adverse effects 1. Due to the long half-life of amiodarone, drug interactions may persist for weeks to months after discontinuation 2. In a drug interaction study, coadministration of letermovir (oral 240 mg once daily) with a CYP3A substrate, midazolam (1 mg single dose IV) led to increased AUC, Cmax and C24hr of midazolam by 47%, 5% and 174%, respectively. And, coadministration of letermovir (oral 240 mg once daily) with midazolam (2 mg single dose orally) led to increased AUC and Cmax of midazolam by 125% and 72%, respectively 1.
Why it happens (mechanism)
Inhibition of CYP3A-mediated metabolism of amiodarone
Literature reports
1 report — tap to read
a) In a drug interaction study, coadministration of letermovir (oral 240 mg once daily) with a CYP3A substrate, midazolam (1 mg single dose IV) led to increased AUC, Cmax and C24hr of midazolam by 47%, 5% and 174%, respectively. And, coadministration of letermovir (oral 240 mg once daily) with midazolam (2 mg single dose orally) led to increased AUC and Cmax of midazolam by 125% and 72%, respectively 1.
Common questions
Can I take Amiodarone and Letermovir Injection together?
Increased amiodarone exposure Always confirm with your pharmacist or prescriber before making any change.
How serious is the Amiodarone and Letermovir Injection 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 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 Amiodarone or Letermovir Injection 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 (2)
- Product Information: PREVYMIS(R) oral tablets, oral pellets, intravenous injection, letermovir oral tablets, oral pellets, intravenous injection. Merck Sharp & Dohme Corp (per FDA), Rahway, NJ, 2024. DailyMed
- Product Information: CORDARONE(R) oral tablets, amiodarone oral tablets. Wyeth Pharmaceuticals Inc (per FDA), Philadephia, PA, 2018. DailyMed
Keep reading about Amiodarone
Keep reading about Letermovir Injection
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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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