Cilostazol and Aspirin: Interaction Details
AI-assisted, pharmacist-reviewed · Source data updated Jul 11, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Cilostazol
Aspirin
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.
What happens
An increased risk of bleeding
Interaction Deep Dive
Concomitant use of aspirin and cilostazol, a platelet aggregation inhibitor, may increase the risk of bleeding events12. Short term clinical studies of aspirin/cilostazol combination therapy revealed an increased risk of bleeding compared with monotherapy. However, long term studies showed no evidence of increased hemorrhagic events 1. If concurrent use is required, administer aspirin and cilostazol with care and Monitor for signs and symptoms of blood loss.
Why it happens (mechanism)
Additive effects
Literature reports
2 reports — tap to read
a) During short term drug interaction studies, coadministration of aspirin and cilostazol resulted in increased inhibition of ex vivo adenosine phosphate-induced platelet aggregation from 22% to 37%. Additionally, ex vivo arachidonic acid-induced platelet aggregation increased by 20% compared to cilostazol monotherapy and by 48% compared with aspirin monotherapy. Short term administration had no effect on prothrombin time, aPTT, or bleeding time 1.
b) During 8 randomized, placebo-controlled, double-blind clinical trials, patients were administered aspirin therapy 75 to 81 mg/day for 137 days (n=107) or 325 mg/day for 54 days (n=85) in combination with cilostazol or placebo. Across the studies, there was no evidence of increased hemorrhagic events in the aspirin/cilostazol group compared with the aspirin/placebo group 1.
Common questions
Can I take Cilostazol and Aspirin together?
An increased risk of bleeding Always confirm with your pharmacist or prescriber before making any change.
How serious is the Cilostazol and Aspirin 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 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 Cilostazol or Aspirin 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)
- Product Information: CILOSTAZOL oral tablets, cilostazol oral tablets. Roxane Laboratories, Inc. (per manufacturer), Columbus, OH, 2011. DailyMed
- Product Information: AGGRENOX(R) oral extended release capsules, aspirin dipyridamole oral extended release capsules. Boehringer Ingelheim Pharmaceuticals, Inc. (per FDA), Ridgefield, CT, 2012. DailyMed
Keep reading about Cilostazol
Keep reading about Aspirin
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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