Apixaban and Letermovir: Interaction Details
AI-assisted, pharmacist-reviewed · AI content regenerated Aug 8, 2026 · Source data updated Jul 11, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Letermovir
Apixaban
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.
Here's what's going on. Letermovir (Prevymis) slows down a liver enzyme called CYP3A that helps your body clear apixaban (Eliquis), a blood thinner. When apixaban is cleared more slowly, more of it can build up in your blood. That means its blood-thinning effect could be a bit stronger, which can raise the chance of bruising or bleeding.
The good news: this is a known, manageable combination. Keep taking both exactly as prescribed and don't change anything on your own. Let your care team know about any unusual bruising, nosebleeds, pink or dark urine, or bleeding that won't stop. They can watch you closely and adjust things if needed.
Mechanism: Letermovir is a moderate CYP3A inhibitor; apixaban is a CYP3A4 (and P-gp) substrate, so inhibition reduces its clearance and increases exposure. Neither drug is a prodrug, so the effect is additive anticoagulant potentiation.
- Direction: Increased apixaban AUC/Cmax, raising bleeding risk.
- Magnitude: Not quantified for apixaban; the midazolam probe showed AUC +47% (IV) to +125% (oral).
- Evidence: Probable; severity major.
- Management: Assess bleeding risk; dose may need to be individualized. Monitor for bleeding signs. Note letermovir is also a P-gp inhibitor, adding to apixaban exposure.
What happens
Increased CYP3A substrate exposure
Interaction Deep Dive
Taking letermovir together with a CYP3A substrate can raise the exposure of that substrate. One drug interaction study examined this: when letermovir (240 mg orally once daily) was given alongside the CYP3A substrate midazolam (single 1 mg IV dose), the midazolam AUC, Cmax, and C24hr rose by 47%, 5%, and 174%, respectively. In the same study, combining letermovir (240 mg orally once daily) with midazolam administered as a single 2 mg oral dose produced increases of 125% in AUC and 72% in Cmax for midazolam1.
Why it happens (mechanism)
Inhibition of CYP3A-substrate metabolism by letermovir
How to manage this interaction
This combination can be managed. Because letermovir can raise apixaban levels and its blood-thinning effect, your care team may take a few steps:
- Keep taking both medications exactly as prescribed unless your prescriber tells you otherwise.
- Your apixaban dose may need to be adjusted and individualized by your care team.
- Your team may monitor you more closely for signs of bleeding.
Tell your pharmacist or doctor right away if you notice unusual bruising, nosebleeds, bleeding gums, blood in urine or stool, or any bleeding that won't stop. Always check before starting or stopping either drug.
Management is individual — confirm any change with your pharmacist or prescriber.
Literature reports
1 report — tap to read
a) In a drug interaction study, giving letermovir (240 mg orally once daily) together with a CYP3A substrate, midazolam (a single 1 mg IV dose), raised midazolam's AUC, Cmax, and C24hr by 47%, 5%, and 174%, respectively. Additionally, giving letermovir (240 mg orally once daily) together with midazolam (a single 2 mg oral dose) raised midazolam's AUC and Cmax by 125% and 72%, respectively 1.
Common questions
Can I take Apixaban and Letermovir together?
Letermovir can raise apixaban levels and increase bleeding risk, so keep taking both as prescribed and watch for unusual bleeding or bruising while your care team monitors you and adjusts the dose if needed. Always confirm with your pharmacist or prescriber before making any change.
How serious is the Apixaban and Letermovir 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 Apixaban and Letermovir interaction managed?
This combination can be managed. Because letermovir can raise apixaban levels and its blood-thinning effect, your care team may take a few steps: Keep taking both medications exactly as prescribed unless your prescriber tells you otherwise. Your apixaban dose may need to be adjusted and individualized by your care team. Your team may monitor you more closely for signs of bleeding. Tell your pharma… Management is individual — always follow your own care team's guidance.
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 Apixaban or Letermovir 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: 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
Keep reading about Letermovir
Keep reading about Apixaban
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.
Check another combination
Our instant two-drug interaction checker is almost here.
Still have questions about this combination?
Every question gets a real answer from a licensed pharmacist — free, and usually within a day.
Ask the pharmacist