Drug Interaction Report

Cilostazol and Ketoconazole Topical: Interaction Details

A pharmacist-reviewed analysis of the Cilostazol and Ketoconazole Topical interaction: the documented clinical effects, severity rating, onset, mechanism, and management considerations, with cited references throughout.

AI-assisted, pharmacist-reviewed · Source data updated Aug 8, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature

Cilostazol

Pletal®
+

Ketoconazole Topical

Extina® Foam Ketozole® Cream Kuric Nizoral AD® Shampoo Nizoral® Cream Nizoral® Shampoo Xolegel®
Dr. Brian Staiger, PharmD, BCPS
Medically reviewed by
Dr. Brian Staiger, PharmD, BCPS
Updated Aug 8, 2026
Editorial policy · Data sources
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Interaction severity
Major
Potentially serious — often needs a change or close monitoring.
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.

Of 78 documented Cilostazol interactions, 65 are rated major — including this one.
Worried about symptoms right now? Contact your pharmacist or prescriber, or call Poison Control at 1-800-222-1222 (US). Call 911 for an emergency.
Onset
unspecified
Evidence
probable
Severity
Major

What happens

Increased cilostazol exposure and an altered (increased/reduced) cilostazol active metabolites exposure

Interaction Deep Dive

Exert caution when cilostazol (CYP3A4 substrate) is coadministered with ketoconazole (CYP3A4 inhibitor), as it may increase cilostazol exposure and may alter (increased/reduced) cilostazol active metabolites exposure. Upon coadministration, monitor patients closely for signs or symptoms of increased or prolonged effects or side effects of cilostazol, and reduce cilostazol dosage as deemed necessary1.

Why it happens (mechanism)

Inhibition of CYP3A4-mediated metabolism of cilostazol

Literature reports

2 reports — tap to read

a) Coadministration of ketoconazole 400 mg and cilostazol 100 mg increased AUC 117% and Cmax 94% 2.

b) Concomitant use of single doses of cilostazol 100 mg and ketoconazole 400 mg approximately doubled cilostazol concentrations and altered (increase/decrease) the concentrations of the active metabolites of cilostazol 1.

Common questions

Can I take Cilostazol and Ketoconazole Topical together?

Increased cilostazol exposure and an altered (increased/reduced) cilostazol active metabolites exposure Always confirm with your pharmacist or prescriber before making any change.

How serious is the Cilostazol and Ketoconazole Topical 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 "probable". Good supporting evidence, though not definitively proven.

Questions for your pharmacist

  • Does my dose of Cilostazol or Ketoconazole Topical 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)

  1. Product Information: Ketoconazole oral tablet, ketoconazole oral tablet. Taro Pharmaceuticals U.S.A. Inc. (per DailyMed), Hawthorne, NY, 2024. DailyMed
  2. Product Information: PLETAL(R) oral tablets, cilostazol oral tablets. Otsuka America Pharmaceutical, Inc. (per FDA), Rockville, MD, 2015. DailyMed
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Cilostazol

Keep reading about Cilostazol

All Cilostazol interactions (78) Cilostazol drug information
Also serious with: Defibrotide Injection Abrocitinib Meloxicam Injection Miconazole Vaginal
Ketoconazole Topical

Keep reading about Ketoconazole Topical

All Ketoconazole Topical interactions (546) Ketoconazole Topical drug information
Also serious with: Colchicine Conivaptan Crizotinib Dabrafenib
Beyond drug–drug

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:

Cilostazol + Activated Charcoal Danshen Grapefruit Piracetam St. John's Wort Acacia Rigidula Aconite Adrafinil + 278 more

major · moderate · minor — check everything you take with our drug–supplement interaction checker.

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This information is for education, not a substitute for professional medical advice. Do not start, stop, or change any medication without talking to your pharmacist or prescriber.