Omeprazole and Cilostazol: 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
Cilostazol
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.
You've been prescribed both cilostazol (Pletal), which helps blood flow in your legs, and omeprazole (Prilosec) for your stomach. Here's the thing: omeprazole slows down one of the liver enzymes that breaks cilostazol down. That means cilostazol can build up a bit higher in your body, and its effects (like headache, dizziness, a racing heartbeat, or loose stools) may feel stronger.
This is based mostly on how these drugs behave in theory, so please don't worry or change anything on your own. Your care team can easily manage this, often by using a lower cilostazol dose. Just check in with your pharmacist or doctor.
Effect: Increased cilostazol exposure via omeprazole inhibition of CYP2C19, a primary pathway for cilostazol metabolism. Cilostazol is active parent drug (not a prodrug), so inhibition raises its levels and pharmacologic activity.
- Direction: Increased cilostazol and active metabolite (3,4-dihydro-cilostazol) concentrations, reported ~26% to 69%.
- Onset: Unspecified. Evidence: Theoretical/PK-based. Severity: Major.
- Management: Consider reducing cilostazol to 50 mg twice daily when coadministration is required. Monitor for dose-related adverse effects (headache, palpitations/tachycardia, diarrhea, hypotension).
What happens
Increased cilostazol exposure
Interaction Deep Dive
When CYP2C19 inhibitors are given alongside cilostazol, cilostazol exposure rises2. In one instance, taking cilostazol together with omeprazole (which inhibits CYP2C19) raised the levels of cilostazol and its active metabolites by 26% to 69%3. If cilostazol must be used concurrently with a CYP2C19 inhibitor, a dose reduction of cilostazol to 50 mg twice daily should be considered21.
Why it happens (mechanism)
Inhibition of CYP2C19-mediated metabolism of cilostazol
How to manage this interaction
Good news: this is a manageable interaction. Keep taking both medicines exactly as prescribed unless your care team tells you otherwise.
- Your prescriber may lower your cilostazol dose (a common approach is 50 mg twice daily) while you're also on omeprazole.
- Your team may watch you a bit more closely for stronger cilostazol effects like headache, dizziness, a fast or pounding heartbeat, or diarrhea.
- Tell your pharmacist or doctor about all your medicines, and mention any new or worsening symptoms.
Don't stop or change either drug on your own. A quick check-in lets your team tailor the dose to you.
Management is individual — confirm any change with your pharmacist or prescriber.
Literature reports
2 reports — tap to read
a) Giving omeprazole together with cilostazol 100 mg raised the AUC of the pharmacologically active 3,4-dehydro-cilostazol metabolite by 69% 2.
b) Taking cilostazol, a CYP2C19 substrate, alongside omeprazole, a CYP2C19 inhibitor, led to higher plasma levels of cilostazol and one of its active metabolites. Twenty healthy nonsmoking volunteers took part in a single-center, open-label study designed to assess how omeprazole affects the pharmacokinetics of a single dose of cilostazol 100 mg. Each participant was given cilostazol 100 mg on day 0 while fasting. From day 7 through day 18, omeprazole 40 mg was administered every morning. An additional single dose of cilostazol 100 mg was given with omeprazole on day 14 3. Following omeprazole dosing, the Cmax of cilostazol rose by 18% (from 782 mcg/L to 921 mcg/L) and the AUC rose by 26% (from 10,287 mcg/L/h to 13,033 mcg/L/hr). The mean Cmax of OPC-13015, a pharmacologically active metabolite of cilostazol, increased by 29% and its AUC increased by 69% when omeprazole was present 31. In contrast, the Cmax and AUC of OPC-13213, another pharmacologically active metabolite of cilostazol, fell by 22% and 31%, respectively. Even though the changes in systemic exposure to cilostazol were well tolerated, the cilostazol dose should be lowered to 50 mg twice daily when it is used concurrently with omeprazole 3.
Common questions
Can I take Omeprazole and Cilostazol together?
Omeprazole can raise cilostazol levels by blocking its breakdown, so your doctor may lower the cilostazol dose (often to 50 mg twice daily) and watch for stronger side effects; keep taking both as prescribed and check with your care team. Always confirm with your pharmacist or prescriber before making any change.
How serious is the Omeprazole and Cilostazol 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 Cilostazol interaction managed?
Good news: this is a manageable interaction. Keep taking both medicines exactly as prescribed unless your care team tells you otherwise. Your prescriber may lower your cilostazol dose (a common approach is 50 mg twice daily) while you're also on omeprazole. Your team may watch you a bit more closely for stronger cilostazol effects like headache, dizziness, a fast or pounding heartbeat, or diarrhea… 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 Cilostazol 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: KONVOMEP(TM) powder for oral suspension, omeprazole sodium bicarbonate powder for oral suspension. Azurity Pharmaceuticals Inc (per manufacturer), Woburn, MA, 2022. DailyMed
- Product Information: PLETAL(R) oral tablets, cilostazol oral tablets. Otsuka America Pharmaceutical, Inc. (per FDA), Rockville, MD, 2015. DailyMed
- Suri A & Bramer SL: Effect of omeprazole on the metabolism of cilostazol. Clin Pharmacokinet 1999; 37(suppl 2):53-59. PubMed
Keep reading about Cilostazol
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