Drug Interaction Report

Silodosin and Ketoconazole Topical: Interaction Details

A pharmacist-reviewed analysis of the Silodosin 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

Ketoconazole Topical

Extina® Foam Ketozole® Cream Kuric Nizoral AD® Shampoo Nizoral® Cream Nizoral® Shampoo Xolegel®
+

Silodosin

Rapaflo Rapaflo®
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
Contraindicated
These should generally not be used together.
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 10 documented Silodosin interactions, 1 is rated contraindicated — 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
Contraindicated

What happens

Increased silodosin exposure

Interaction Deep Dive

Concomitant use of silodosin and strong CYP3A4 inhibitors is contraindicated as it may increase silodosin exposure. Concomitant administration of a single oral dose of silodosin 8 mg and ketoconazole 400 mg (a strong CYP3A4 inhibitor) once daily for 4 days during 2 clinical metabolic inhibition studies revealed a 3.8-fold increase in silodosin maximum plasma concentrations and a 3.2-fold increase in silodosin exposure. Similarly, coadministration of silodosin 4 mg and ketoconazole 200 mg results in a 3.7-fold increase of silodosin maximum plasma concentration and 2.9-fold increase of silodosin exposure1.

Why it happens (mechanism)

Inhibition of CYP3A4-mediated metabolism of silodosin

Literature reports

2 reports — tap to read

a) In a clinical metabolic inhibition study, concomitant administration of a single oral dose of silodosin 8 mg and ketoconazole 400 mg (a strong CYP3A4 inhibitor), caused a 3.8-fold increase in silodosin maximum plasma concentrations and a 3.2-fold increase in silodosin exposure (AUC) 1.

b) In a drug interaction study, coadministration of silodosin 4 mg and ketoconazole 200 mg results in a 3.7-fold increase of silodosin maximum plasma concentration and 2.9-fold increase of silodosin exposure 1.

Common questions

Can I take Silodosin and Ketoconazole Topical together?

Increased silodosin exposure Always confirm with your pharmacist or prescriber before making any change.

How serious is the Silodosin and Ketoconazole Topical interaction?

It is rated contraindicated. These should generally not be used together.

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 Silodosin 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 (1)

  1. Product Information: RAPAFLO(R) oral capsules, silodosin oral capsules. Allergan USA Inc (per manufacturer), Irvine, CA, 2017. DailyMed
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Ketoconazole Topical

Keep reading about Ketoconazole Topical

All Ketoconazole Topical interactions (546) Ketoconazole Topical drug information
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Silodosin

Keep reading about Silodosin

All Silodosin interactions (10) Silodosin drug information
Also serious with: Alfuzosin Cyclosporine Injection Cyclosporine Ophthalmic Doxazosin
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:

Silodosin + Activated Charcoal Grapefruit St. John's Wort Acacia Rigidula Adrafinil African Wild Potato American Elder Astaxanthin + 137 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.