Fexinidazole and Letermovir Injection: Interaction Details
AI-assisted, pharmacist-reviewed · Source data updated Aug 8, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Fexinidazole
No brand names on recordLetermovir 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
Reduced exposure of active fexinidazole metabolites and potential decreased efficacy of fexinidazole
Interaction Deep Dive
Avoid concomitant use of fexinidazole (a CYP3A4 substrate) with CYP3A4 inhibitors. If coadministration cannot be avoided, monitor for lack of efficacy of fexinidazole due to potential for decreased plasma concentrations of the active fexinidazole M1 and M2 metabolites1.
Why it happens (mechanism)
Inhibition of CYP3A4-mediated metabolism of fexinidazole
Common questions
Can I take Fexinidazole and Letermovir Injection together?
Reduced exposure of active fexinidazole metabolites and potential decreased efficacy of fexinidazole Always confirm with your pharmacist or prescriber before making any change.
How serious is the Fexinidazole 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 Fexinidazole 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: Fexinidazole oral tablets, fexinidazole oral tablets. sanofi-aventis US LLC (per FDA), Bridgewater, NJ, 2021. DailyMed
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