Omeprazole and Ensitrelvir: Interaction Details
AI-assisted, pharmacist-reviewed · AI content regenerated Jul 11, 2026 · Source data updated Jul 2, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Omeprazole
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.
These two medicines can clash. Ensitrelvir is an antiviral that strongly slows down a liver enzyme (called CYP3A) that your body uses to break down many other drugs. Omeprazole, your stomach acid medicine, is partly cleared by that same enzyme. So while you are taking ensitrelvir, omeprazole (and other CYP3A drugs) can build up higher than normal, which can raise the chance of side effects.
Because of this, taking them together is generally not recommended. The good news is this is very manageable. Do not stop either one on your own. Just tell your pharmacist or doctor about every medicine you take so they can time things safely or pick a better option.
Mechanism: Ensitrelvir is a potent CYP3A inhibitor. Coadministration reduces CYP3A-mediated metabolism of CYP3A substrates, increasing their exposure and risk of concentration-related adverse effects.
- Direction: Increased substrate exposure (Cmax/AUC). Illustrative probe data: midazolam AUC increased ~6.8-fold, Cmax ~2.8-fold; dexamethasone AUC ~3.5-fold on day 5, with residual inhibition persisting ~10 days post-dose.
- Evidence: Probable. Severity: Contraindicated per labeling.
- Management: Initiate ensitrelvir only after evaluating concomitant CYP3A substrates. Given omeprazole is a CYP3A substrate, consider holding/alternative; reinitiate substrate based on duration of CYP3A inhibition (residual effect for days after last dose) and patient factors.
What happens
Increased CYP3A substrates exposure and an increased risk of CYP3A substrates-related adverse effects
Interaction Deep Dive
Co-administration of ensitrelvir with CYP3A substrates is contraindicated because it can raise the exposure of those substrates and potentially produce adverse effects. In drug interaction studies, giving midazolam (a CYP3A substrate) as a single 2 mg oral dose alongside ensitrelvir at the clinical dose (375 mg on day 1 followed by 125 mg on days 2 to 5) on Day 5 produced roughly a 2.80-fold rise in midazolam Cmax and a 6.77-fold rise in AUC(0 to inf) relative to midazolam given by itself. Similarly, when dexAMETHasone (a single 1 mg dose) was administered with ensitrelvir (750 mg on day 1 and 250 mg on days 2 to 5, which is twice the recommended dose) on day 5, and dexAMETHasone was given alone on day 9 (5 days after the final ensitrelvir dose) and day 14 (10 days after the final ensitrelvir dose), the results compared to dexAMETHasone given alone were: an approximately 1.47-fold increase in Cmax and a 3.47-fold increase in AUC(0 to inf) on day 5; a 1.24-fold increase in Cmax and a 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. Ensitrelvir should be started only after careful assessment of the pertinent clinical and pharmacokinetic factors associated with the concomitant medication. Furthermore, restarting contraindicated CYP3A substrates should be considered based on evaluating how long CYP3A inhibition persists together with patient specific considerations1.
Why it happens (mechanism)
Inhibition of CYP3A-mediated metabolism by ensitrelvir
How to manage this interaction
What your care team may do:
- Review all your medicines before starting ensitrelvir, since it can raise levels of drugs cleared by CYP3A, including omeprazole.
- Possibly pause or switch one medicine, or choose an alternative acid-reducing option.
- Wait an appropriate time before restarting the affected medicine, because the enzyme-blocking effect can linger for several days after the last ensitrelvir dose.
What you should do: Keep taking both exactly as prescribed until you get guidance. Do not start, stop, or change either medicine on your own. Tell your pharmacist or prescriber that you take omeprazole before any ensitrelvir course is started.
Management is individual — confirm any change with your pharmacist or prescriber.
Literature reports
1 report — tap to read
a) When midazolam (a CYP3A substrate) was given as a single 2 mg oral dose together with ensitrelvir at the clinical dose (375 mg on day 1 and 125 mg on days 2 to 5) on Day 5, the Cmax of midazolam rose approximately 2.80-fold and its AUC(0 to inf) rose 6.77-fold relative to midazolam given by itself. In addition, when dexAMETHasone (a single 1 mg dose) was co-administered with ensitrelvir (750 mg on day 1 and 250 mg on days 2 to 5, which is twice the recommended dose) on day 5 and was given alone on day 9 (5 days after the final ensitrelvir dose) and on day 14 (10 days after the final ensitrelvir dose), the dexAMETHasone Cmax increased approximately 1.47-fold and its AUC(0 to inf) increased 3.47-fold on day 5, its Cmax increased 1.24-fold and its AUC(0 to inf) increased 2.38-fold on day 9, and its Cmax increased 1.17-fold and its AUC(0 to inf) increased 1.58-fold on day 14, compared with dexAMETHasone given alone 1.
Common questions
Can I take Omeprazole and Ensitrelvir together?
Ensitrelvir strongly blocks the CYP3A enzyme and can raise levels of omeprazole and other CYP3A drugs, so combining them is generally contraindicated. Do not change anything yourself; have your pharmacist or doctor review your medicines before ensitrelvir is used. Always confirm with your pharmacist or prescriber before making any change.
How serious is the Omeprazole 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 is the Omeprazole and Ensitrelvir interaction managed?
What your care team may do: Review all your medicines before starting ensitrelvir, since it can raise levels of drugs cleared by CYP3A, including omeprazole. Possibly pause or switch one medicine, or choose an alternative acid-reducing option. Wait an appropriate time before restarting the affected medicine, because the enzyme-blocking effect can linger for several days after the last ensitrelvir… 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 Omeprazole 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.
Keep reading about Omeprazole
Keep reading about Ensitrelvir
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