Omeprazole and Nivolumab: 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
Nivolumab
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.
You've been prescribed nivolumab (Opdivo), a type of immunotherapy that helps your immune system fight cancer. You're also taking omeprazole (Prilosec), a common acid-reducing medicine. Here's the concern: studies in certain cancers found that people taking a stomach acid blocker like omeprazole along with nivolumab didn't do as well, meaning the immunotherapy may not work as strongly.
The likely reason is that these acid reducers change the mix of bacteria in your gut, and that gut balance seems to play a role in how well immunotherapy works. Please don't stop either medicine on your own. Talk with your oncology team. They can look at whether you truly need the acid reducer and manage this together with you.
Effect: Reduced nivolumab efficacy. Concurrent PPI use has been associated with decreased progression-free and overall survival in metastatic renal cell carcinoma (MRCC) and gastric cancer (GC) treated with nivolumab.
Mechanism: Not a pharmacokinetic interaction. PPIs alter GI microbiota composition, which appears to impair the immune milieu supporting checkpoint-inhibitor response (proposed effects on NK cytotoxicity and neutrophil function). Neither agent is metabolically dependent on the other.
- Direction/magnitude: Pharmacodynamic; reduced clinical benefit. Onset unspecified.
- Evidence: Probable (observational).
- Management: Critically reassess PPI necessity; use lowest effective acid suppression or consider alternatives (eg, H2RA) if clinically appropriate. Decisions individualized by oncology.
What happens
Reduced efficacy of nivolumab
Interaction Deep Dive
In patients with metastatic renal cell carcinoma (MRCC)1 and gastric cancer (GC)2 receiving nivolumab, the simultaneous administration of proton pump inhibitors (PPI) was linked to reductions in both progression-free survival and overall survival. Because of this, clinicians should give careful thought to using PPIs alongside nivolumab in individuals with MRCC1 and GC2.
Why it happens (mechanism)
Modified gastrointestinal microbiota by proton pump inhibitors; disruption of immune system physiological function; detrimental effect on cytotoxic activity of natural killer cells and neutrophil functions
How to manage this interaction
Keep taking both medicines exactly as prescribed unless your care team tells you otherwise. This interaction is about the immunotherapy possibly working less well, so it's worth a conversation.
- Ask your oncology team whether you still need the acid reducer, or whether a lower dose or a different type of stomach medicine might be an option.
- Let them know why you take omeprazole (heartburn, reflux, stomach protection) so they can weigh the benefits against this concern.
- Don't stop your acid reducer on your own, since some people need it for real reasons.
Your team can tailor this to your situation and monitor your treatment response.
Management is individual — confirm any change with your pharmacist or prescriber.
Literature reports
2 reports — tap to read
a) A single-center retrospective study evaluated 80 adult patients with advanced or recurrent gastric or gastroesophageal junction cancer who were treated with nivolumab monotherapy. Concurrent administration of proton pump inhibitors (PPIs; n=33) correlated with a significantly reduced median progression-free survival (PFS) relative to patients not receiving PPIs (3.61 vs 9.43 months; HR, 2.21 [95% CI, 1.2 to 4.06]), and also with a significantly reduced median overall survival (OS) on univariate analysis (4.83 vs 16.4 months; HR, 2.24 [95% CI, 1.24 to 4.05]). Within the subgroup of patients taking PPIs, those who had undergone a prior gastrectomy showed a significantly longer median PFS (10.2 vs 3.65 months; HR, 0.51 [95% CI, 0.28 to 0.93]) and OS (22.2 vs 6.4 months; HR, 0.43 [95% CI, 0.24 to 0.78]) compared with patients who had not had a gastrectomy. The authors proposed that alterations in the gut microbiome and elevated gastrin concentrations promoting tumor progression as a result of PPI use might play a role in the interaction 2.
b) A multicenter retrospective study included 109 patients with metastatic renal cell carcinoma who received second-line nivolumab therapy, of whom 59 patients were not taking a concurrent proton pump inhibitor (PPI) and 50 were taking a PPI. The median progression-free survival (PFS) was 6.37 (5.2 to 7.5) months in the concurrent PPI group and 9.7 (4.5 to 15) months in the non-PPI group (no PPI vs PPI, HR 0.44; 95% CI 0.28 to 0.96). The median overall survival (OS) was 14.6 (7.1 to 22.1) months among patients receiving a PPI and 29.9 (17.1 to 42.7) months among non-users (no PPI vs PPI, HR 0.68; 95% CI 0.22 to 0.88). The PPIs administered were pantoprazole 40 mg, esomeprazole 40 mg, lansoprazole 30 mg, or omeprazole 40 mg. The mean length of PPI use was 3.95 months, and the median follow-up duration was 14.5 months. Additional variables assessed included best response to nivolumab, side effects of any grade, and grade 3/4 side effects; no difference was observed between concurrent PPI users and non-users. PFS and OS were identified as independent risk factors 1.
Common questions
Can I take Omeprazole and Nivolumab together?
Taking omeprazole with nivolumab may make the immunotherapy work less well, so ask your oncology team whether you truly need the acid reducer or whether an alternative fits your situation. Do not stop either medicine on your own. Always confirm with your pharmacist or prescriber before making any change.
How serious is the Omeprazole and Nivolumab 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 Nivolumab interaction managed?
Keep taking both medicines exactly as prescribed unless your care team tells you otherwise. This interaction is about the immunotherapy possibly working less well, so it's worth a conversation. Ask your oncology team whether you still need the acid reducer, or whether a lower dose or a different type of stomach medicine might be an option. Let them know why you take omeprazole (heartburn, reflux,… 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 Nivolumab 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 (2)
- Ugrakli M, Kocak MZ, Dinc G, et al: The effect of concomitant proton pump inhibitor use on survival outcomes of nivolumab-treated renal cell carcinoma patients: a multicenter study. J Cancer Res Clin Oncol 2023; 149(11):9183-9189. PubMed
- Shibano M, Takahashi M, Nakatsukasa H, et al: Proton pump inhibitors reduce nivolumab efficacy in unresectable advanced or recurrent gastric cancer. Immunotherapy 2025; 17(5):331-338. PubMed
Keep reading about Omeprazole
Keep reading about Nivolumab
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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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