Omeprazole and Tazemetostat: 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
Tazemetostat
Omeprazole
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.
Here's what's going on with tazemetostat (Tazverik) and omeprazole (Prilosec). Tazemetostat can speed up an enzyme in your body called CYP3A. Since omeprazole is partly broken down by that enzyme, your body may clear it a little faster, which could make it work less well at controlling stomach acid.
In plain terms, your heartburn or reflux protection might not be as strong while you take both. The good news is this is very manageable. Don't change anything on your own, but do let your pharmacist or doctor know you take both so they can watch how well the omeprazole is working and adjust if needed.
Effect: Tazemetostat is a CYP3A inducer; omeprazole is partly a CYP3A substrate, so coadministration may lower omeprazole exposure and reduce its acid-suppressing efficacy.
- Mechanism: Induction of CYP3A-mediated metabolism by tazemetostat (direction: reduced substrate exposure).
- Magnitude: With sensitive substrate midazolam, tazemetostat 800 mg BID reduced AUC by 40% and Cmax by 21%.
- Onset: Unspecified; evidence: probable.
- Management: Monitor for reduced omeprazole efficacy (breakthrough reflux/dyspepsia). Dose may be individualized by the care team; consider alternative acid suppression if response is inadequate.
What happens
Reduced CYP3A substrate exposure and reduced efficacy of CYP3A substrate
Interaction Deep Dive
When tazemetostat is taken together with CYP3A substrates, the exposure to those substrates may fall, which can diminish their effectiveness. A drug interaction study in patients showed that giving tazemetostat 800 mg twice daily along with oral midazolam (a sensitive CYP3A substrate) lowered the AUC of midazolam by 40% and its Cmax by 21%1.
Why it happens (mechanism)
Induction of CYP3A-substrate metabolism by tazemetostat
How to manage this interaction
Keep taking both medicines as prescribed unless your care team tells you otherwise. Because tazemetostat can lower how well omeprazole works, here is how a care team usually handles this:
- Watch for signs the omeprazole may not be working as well, such as returning heartburn, reflux, or stomach discomfort.
- Your omeprazole dose may need to be adjusted and individualized by your care team, or an alternative acid-reducing medicine may be considered if your symptoms return.
- Report any breakthrough symptoms to your pharmacist or prescriber so they can monitor you more closely.
Management is individual — confirm any change with your pharmacist or prescriber.
Literature reports
1 report — tap to read
a) In a drug interaction study, giving tazemetostat 800 mg twice daily together with oral midazolam (a sensitive CYP3A substrate) to patients reduced the AUC and Cmax of midazolam by 40% and 21%, respectively 1.
Common questions
Can I take Omeprazole and Tazemetostat together?
Tazemetostat can make omeprazole work less well by speeding up its breakdown, so watch for returning reflux or heartburn and tell your pharmacist or doctor, who can adjust your treatment if needed. Always confirm with your pharmacist or prescriber before making any change.
How serious is the Omeprazole and Tazemetostat 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 is the Omeprazole and Tazemetostat interaction managed?
Keep taking both medicines as prescribed unless your care team tells you otherwise. Because tazemetostat can lower how well omeprazole works, here is how a care team usually handles this: Watch for signs the omeprazole may not be working as well, such as returning heartburn, reflux, or stomach discomfort. Your omeprazole dose may need to be adjusted and individualized by your care team, or an alte… 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 Tazemetostat 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: TAZVERIK(R) oral tablets, tazemetostat oral tablets. Epizyme Inc (per FDA), Cambridge, MA, 2024. DailyMed
Keep reading about Tazemetostat
Keep reading about Omeprazole
These medications also interact with supplements
Prescription drugs aren't the whole picture — herbal and dietary supplements can interact with them too. From the evidence-graded Natural Medicines database:
major · moderate · minor — check everything you take with our drug–supplement interaction checker.
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