Drug Interaction Report

Conjugated / Estrogens and Ketoconazole Topical: Interaction Details

A pharmacist-reviewed analysis of the Conjugated / Estrogens 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®
+

Conjugated / Estrogens

Premarin
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 5 documented Conjugated / Estrogens interactions, 2 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
theoretical
Severity
Major

What happens

Increased conjugated estrogens exposure and an increased risk of conjugated estrogens-related adverse effects

Interaction Deep Dive

Concomitant use of conjugated estrogens with a strong CYP3A4 inhibitor may increase exposure of estrogens and may result in side effects12.

Why it happens (mechanism)

Inhibition of CYP3A4-mediated metabolism of conjugated estrogens

Literature reports

1 report — tap to read

a) In in-vivo studies have shown that estrogens are metabolized partially by CYP3A). Therefore, inhibitors of CYP3A4 may affect estrogen drug metabolism. Inhibitors of CYP3A4, such as erythromycin, clarithromycin, ketoconazole, itraconazole, ritonavir and grapefruit juice, may increase plasma concentrations of estrogens and may result in side effects 12.

Common questions

Can I take Conjugated / Estrogens and Ketoconazole Topical together?

Increased conjugated estrogens exposure and an increased risk of conjugated estrogens-related adverse effects Always confirm with your pharmacist or prescriber before making any change.

How serious is the Conjugated / Estrogens 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 "theoretical". Predicted from the drugs' pharmacology; not yet confirmed in people.

Questions for your pharmacist

  • Does my dose of Conjugated / Estrogens 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: PREMARIN(R) oral film coated tablets, conjugated estrogen oral film coated tablets. Wyeth Pharmaceuticals LLC (per Dailymed), Philadelphia, PA, 2024. DailyMed
  2. Product Information: PREMARIN vaginal cream, conjugated estrogen vaginal cream. Wyeth Pharmaceuticals LLC (per Dailymed), Philadelphia, PA, 2024. DailyMed
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Ketoconazole Topical

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All Ketoconazole Topical interactions (546) Ketoconazole Topical drug information
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Conjugated / Estrogens

Keep reading about Conjugated / Estrogens

All Conjugated / Estrogens interactions (5) Conjugated / Estrogens drug information
Also serious with: Hydroxychloroquine

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