Omeprazole and Erythromycin: 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
Erythromycin
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 these two. Erythromycin is an antibiotic that can slow down a liver enzyme called CYP3A4. This enzyme helps your body break down and clear out many other medicines. When it's slowed down, those other medicines can build up a little higher than usual, which can make both their helpful effects and their side effects stronger or last longer.
The good news: this concern is mostly theoretical, and your care team knows how to handle it. They may adjust a dose or keep a closer eye on how you're doing. Just make sure your pharmacist and doctor know you're taking both, and don't change anything on your own.
Mechanism: Erythromycin is a moderate CYP3A4 inhibitor. Co-administered CYP3A4 substrates may show reduced hepatic/intestinal metabolism, increasing substrate AUC and Cmax, with potential for enhanced or prolonged therapeutic and adverse effects.
- Direction: increased substrate exposure (erythromycin inhibits; neither agent here is affected as a prodrug).
- Severity/Evidence: rated major, but substantiation is theoretical; onset unspecified.
- Management: consider substrate dose adjustment individualized to the patient; where feasible, monitor substrate concentrations and for substrate-specific toxicity. Exercise particular caution with narrow-therapeutic-index CYP3A4 substrates.
What happens
Increased CYP3A4 substrate exposure and an increased risk of CYP3A4-substrate-related adverse effects
Interaction Deep Dive
When erythromycin is taken together with CYP3A4 substrates, the exposure to those substrates may rise, potentially heightening or extending their therapeutic as well as adverse effects. In patients receiving erythromycin at the same time as CYP3A4 substrates, dosage modifications should be considered and, where feasible, the drug concentrations of the CYP3A4 substrates should be monitored closely123.
Why it happens (mechanism)
Inhibition of CYP3A4-mediated metabolism by erythromycin
How to manage this interaction
How your care team typically handles this:
- They may adjust the dose of the affected medication and individualize it to you.
- Where possible, they may monitor drug levels or watch more closely for side effects.
- They may space out timing or, in some cases, choose an alternative.
What you should do: keep taking both medicines exactly as prescribed unless told otherwise. Let your pharmacist or prescriber know you're on both, and report any new or stronger side effects. Remember, erythromycin is usually a short course, so this concern is often temporary.
Management is individual — confirm any change with your pharmacist or prescriber.
Common questions
Can I take Omeprazole and Erythromycin together?
Erythromycin can slow how your body clears certain other medicines, so their effects and side effects may be stronger while you take it. Keep taking both as prescribed and let your pharmacist or doctor know so they can adjust the dose or monitor you. Always confirm with your pharmacist or prescriber before making any change.
How serious is the Omeprazole and Erythromycin 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 Erythromycin interaction managed?
How your care team typically handles this: They may adjust the dose of the affected medication and individualize it to you. Where possible, they may monitor drug levels or watch more closely for side effects. They may space out timing or, in some cases, choose an alternative. What you should do: keep taking both medicines exactly as prescribed unless told otherwise. Let your pharmacist or prescrib… Management is individual — always follow your own care team's guidance.
How strong is the evidence for this interaction?
The evidence is graded "theoretical". Predicted from the drugs' pharmacology; not yet confirmed in people.
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 Erythromycin 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 (3)
- Product Information: Erythromycin Lactobionate IV injection lyophilized powder for solution, erythromycin lactobionate IV injection lyophilized powder for solution. Nexus Pharmaceuticals (per DailyMed), Lincolnshire, IL, 2024.
- Product Information: Erythromycin oral delayed-release capsules, erythromycin oral delayed-release capsules. Dr. Reddy's Laboratories Inc. (per DailyMed), Princeton, NJ, 2025. DailyMed
- Product Information: ERYTHROMYCIN ETHYLSUCCINATE oral suspension granule, erythromycin ethylsuccinate oral suspension granule. ANI Pharmaceuticals, Inc (per DailyMed), Baudette, MN, 2025. DailyMed
Keep reading about Erythromycin
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.
Check another combination
Our instant two-drug interaction checker is almost here.
Still have questions about this combination?
Every question gets a real answer from a licensed pharmacist — free, and usually within a day.
Ask the pharmacist