Palovarotene 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
Palovarotene
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 palovarotene exposure and an increased risk of palovarotene-related adverse effects
Interaction Deep Dive
Concomitant use of palovarotene (a CYP3A4 substrate) with a moderate CYP3A4 inhibitor may increase the palovarotene exposure, which may increase the risk of palovarotene-related adverse reactions. In the drug interaction studies, coadministration of palovarotene with erythromycin (a moderate CYP3A4 inhibitor) increased the Cmax and AUC of palovarotene by 1.6 and 2.5-fold, respectively. Avoid concomitant use of a moderate CYP3A4 inhibitor with palovarotene, if possible. If coadministration of palovarotene with moderate CYP3A4 inhibitors is required, reduce the palovarotene dose by half1.
Why it happens (mechanism)
Inhibition of CYP3A4-mediated metabolism of palovarotene
Literature reports
1 report — tap to read
a) In the drug interaction studies, coadministration of palovarotene with erythromycin (a moderate CYP3A4 inhibitor) increased the Cmax and AUC of palovarotene by 1.6 and 2.5-fold, respectively 1.
Common questions
Can I take Palovarotene and Letermovir Injection together?
Increased palovarotene exposure and an increased risk of palovarotene-related adverse effects Always confirm with your pharmacist or prescriber before making any change.
How serious is the Palovarotene 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.
Questions for your pharmacist
- Does my dose of Palovarotene 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: SOHONOS(TM) oral capsules, palovarotene oral capsules. Ipsen Biopharmaceuticals Inc (per FDA), Cambridge, MA, 2023. DailyMed
Keep reading about Letermovir Injection
Keep reading about Palovarotene
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