Irinotecan Injection and Ensitrelvir: Interaction Details
AI-assisted, pharmacist-reviewed · Source data updated Aug 8, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Irinotecan Injection
Ensitrelvir
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 CYP3A/BCRP substrate exposure and an increased risk of adverse reactions
Interaction Deep Dive
Concomitant administration of ensitrelvir and CYP3A substrates that are also BCRP substrates is contraindicated as it may increase the exposure of CYP3A/BCRP substrates and may cause adverse effects. Consider initiation of ensitrelvir only after careful evaluation of relevant clinical and pharmacokinetic factors related to the concomitant medication. In addition, consider reinitiation of contraindicated CYP3A substrates based on an assessment of the duration of CYP3A inhibition and patient specific considerations1.
Why it happens (mechanism)
Inhibition of BCPR-mediated efflux transport by ensitrelvir; inhibition of CYP3A-mediated metabolism by ensitrelvir
Literature reports
2 reports — tap to read
a) Concomitant administration of midazolam (CYP3A substrate) (2 mg single oral dose) with ensitrelvir at the clinical dose (375 mg on day 1 and 125 mg on days 2-5) on Day 5 resulted in an approximately 2.80-fold increase in Cmax and a 6.77-fold increase in AUC(0 to inf) of midazolam compared to midazolam administered alone. And, concomitant administration of dexAMETHasone (1 mg single dose) with ensitrelvir (750 mg on day 1 and 250 mg on days 2-5, two fold of the recommended dose) on day 5 and administered alone on day 9 (5 days after the last ensitrelvir dose) and day 14 (10 days after the last ensitrelvir dose) resulted in an approximately 1.47-fold increase in Cmax and a 3.47-fold increase in AUC(0 to inf) of dexAMETHasone on day 5, a 1.24-fold increase in Cmax and 2.38-fold increase in AUC(0 to inf) on day 9, and a 1.17-fold increase in Cmax and a 1.58-fold increase in AUC(0 to inf) on day 14, compared to dexAMETHasone administered alone 1.
b) Concomitant administration of ensitrelvir (500 mg single dose, not a recommended dosage of ensitrelvir) with a single oral dose of a transporter cocktail containing 2.5 mg rosuvastatin (BCRP substrate) resulted in a 1.97-fold increase in Cmax and 1.65-fold increase in AUC(0 to inf) of rosuvastatin 1.
Common questions
Can I take Irinotecan Injection and Ensitrelvir together?
Increased CYP3A/BCRP substrate exposure and an increased risk of adverse reactions Always confirm with your pharmacist or prescriber before making any change.
How serious is the Irinotecan Injection and Ensitrelvir interaction?
It is rated contraindicated. These should generally not be used together.
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 Irinotecan Injection or Ensitrelvir 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: XOCOVA® oral tablets, ensitrelvir oral tablets. Shionogi Inc. Florham Park, NJ, 2026. DailyMed
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