Atezolizumab and Omeprazole: 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
Atezolizumab
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.
Omeprazole (Prilosec) may make your cancer treatment atezolizumab (Tecentriq) work less well. Here's the idea: atezolizumab helps your own immune system fight cancer, and a healthy mix of bacteria in your gut seems to help that immune response. Omeprazole and other acid-reducing drugs (PPIs) can lower the variety of those gut bacteria, which may blunt how well the cancer medicine works.
In a large look-back at lung cancer studies, people taking a PPI didn't do as well on atezolizumab. Please don't stop anything on your own. Talk with your oncology team. They can decide if you still need the PPI or if there's a better option.
Effect: Reduced atezolizumab efficacy (diminished OS and PFS benefit).
Mechanism: PPI-induced reduction in gut microbiome diversity, which impairs the immune-mediated antitumor response to this PD-L1 inhibitor. This is a PD, microbiome-mediated effect, not a CYP interaction; neither drug's activation is enzyme-dependent here.
Evidence: Established. Post-hoc pooled analysis of 5 pivotal NSCLC trials showed significantly lower OS/PFS benefit with concurrent PPI use.
- Evaluate ongoing clinical need for the PPI.
- Consider discontinuation prior to initiating atezolizumab if clinically appropriate.
- Consider H2-blocker or non-pharmacologic alternatives for acid control.
Onset: Unspecified; relevant across the pre-treatment and treatment period.
What happens
Impaired efficacy of atezolizumab
Interaction Deep Dive
Giving proton pump inhibitors (PPIs) before and throughout atezolizumab treatment may reduce how well atezolizumab works. A post-hoc analysis that pooled data from 5 pivotal NSCLC trials found that PPI use, versus not using a PPI, was linked to a significant reduction in the size of the OS and PFS benefit provided by atezolizumab. Assess whether a PPI is clinically necessary and, when feasible, consider stopping it before starting atezolizumab1.
Why it happens (mechanism)
Decrease in gut bacteria diversity by proton pump inhibitors
How to manage this interaction
Keep taking both exactly as prescribed until your care team advises otherwise. This interaction is best handled by your oncology team, not by stopping anything on your own.
- Your team will review whether you truly need the PPI (omeprazole) during atezolizumab therapy.
- If it isn't essential, they may consider stopping it before or during treatment, ideally before atezolizumab starts.
- Ask whether a different acid-control approach might work for you if you still have reflux or stomach symptoms.
Bring up any heartburn or stomach concerns so they can tailor the plan and keep your cancer treatment as effective as possible.
Management is individual — confirm any change with your pharmacist or prescriber.
Literature reports
1 report — tap to read
a) A post-hoc analysis combining data from 5 pivotal trials (IMpower130, IMpower131, IMpower150, OAK, and POPLAR) in patients with NSCLC (N=4458) evaluated PPI use (any use recorded as continuing during treatment; n=1225; omeprazole, n=559; pantoprazole, n=391; esomeprazole, n=136; lansoprazole, n=104; rabeprazole, n=27; dexlansoprazole, n=5; vanoprazan, n=3). PPI use was linked to a significant reduction in the size of the atezolizumab overall survival (OS) benefit (measured by the HR of atezolizumab vs comparator arms) relative to patients not using a PPI (HR 1; 95% CI, 0.85 to 1.17 vs HR, 0.76; 95% CI, 0.69 to 0.83). PPI use likewise showed a significant reduction in the size of the progression-free survival (PFS) benefit with atezolizumab (HR 0.93; 95% CI, 0.76 to 1.13 vs HR, 0.75; 95% CI, 0.65 to 0.88). The findings were consistent across the trials, pointing to a reduced atezolizumab OS benefit whether it was used as first-line chemoimmunotherapy or as later line monotherapy. Among patients randomized to atezolizumab (n=2723), PPI use was associated with significantly poorer OS (adjusted HR, 1.23; 95% CI, 1.09 to 1.37) and PFS (adjusted HR, 1.15; 95% CI, 1.03 to 1.28) compared with those not using a PPI. In the comparator arms randomized to therapy without atezolizumab (n=1735), no significant association was found between PPI use and changes in OS or PFS 1.
Common questions
Can I take Atezolizumab and Omeprazole together?
Omeprazole may reduce how well atezolizumab works by lowering gut bacteria diversity, so ask your oncology team whether you still need the PPI. Do not start or stop anything on your own. Always confirm with your pharmacist or prescriber before making any change.
How serious is the Atezolizumab and Omeprazole 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 Atezolizumab and Omeprazole interaction managed?
Keep taking both exactly as prescribed until your care team advises otherwise. This interaction is best handled by your oncology team, not by stopping anything on your own. Your team will review whether you truly need the PPI (omeprazole) during atezolizumab therapy. If it isn't essential, they may consider stopping it before or during treatment, ideally before atezolizumab starts. Ask whether a d… Management is individual — always follow your own care team's guidance.
How strong is the evidence for this interaction?
The evidence is graded "established". Well documented — supported by controlled studies or strong clinical data.
From our Q&A
Real reader questions about these medications, each personally answered by our pharmacist:
Questions for your pharmacist
- Does my dose of Atezolizumab or Omeprazole 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)
- Hopkins AM, Badaoui S, Kichenadasse G, et al: Efficacy of atezolizumab in patients with advanced NSCLC receiving concomitant antibiotic or proton pump inhibitor treatment: pooled analysis of five randomized control trials. J Thorac Oncol 2022; 17(6):758-767. PubMed
Keep reading about Omeprazole
Keep reading about Atezolizumab
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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