Sirolimus Protein-Bound and Letermovir Injection: Interaction Details
AI-assisted, pharmacist-reviewed · Source data updated Aug 8, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Letermovir Injection
Sirolimus Protein-Bound
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.
What happens
Increased concentrations of sirolimus
Interaction Deep Dive
Concomitant use of sirolimus (a CYP3A4 substrate) with a moderate or weak CYP3A4 inhibitor may increase sirolimus concentrations, which may increase the risk for adverse reactions. If sirolimus protein-bound is used concomitantly with a moderate or weak CYP3A4 inhibitor reduce the dosage of sirolimus protein-bound to 56 mg/m(2)1.
Why it happens (mechanism)
Inhibition of CYP3A4-mediated metabolism of sirolimus
Common questions
Can I take Sirolimus Protein-Bound and Letermovir Injection together?
Increased concentrations of sirolimus Always confirm with your pharmacist or prescriber before making any change.
How serious is the Sirolimus Protein-Bound 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 "theoretical". Predicted from the drugs' pharmacology; not yet confirmed in people.
Questions for your pharmacist
- Does my dose of Sirolimus Protein-Bound 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 (1)
- Product Information: FYARRO(TM) intravenous injection, sirolimus protein-bound intravenous injection. Aadi Bioscience Inc (per FDA), Pacific Palisades, CA, 2021. DailyMed
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