Ketoconazole Topical and Oxybutynin: Interaction Details
AI-assisted, pharmacist-reviewed · Source data updated Aug 8, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Oxybutynin
Ketoconazole Topical
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
Increased oxybutynin plasma concentrations
Interaction Deep Dive
Oxybutynin is metabolized primarily by the CYP3A4 isoenzyme in the liver and gut wall. Concomitant administration with a strong CYP3A4 inhibitor, such as ketoconazole, led to approximately 3-4 fold higher mean oxybutynin chloride plasma levels. Therefore, use caution if these agents are coadministered12. Monitor patients for increased oxybutynin adverse effects (dry mouth, constipation, headache).
Why it happens (mechanism)
Inhibition of CYP3A4-mediated oxybutynin metabolism
Common questions
Can I take Ketoconazole Topical and Oxybutynin together?
Increased oxybutynin plasma concentrations Always confirm with your pharmacist or prescriber before making any change.
How serious is the Ketoconazole Topical and Oxybutynin interaction?
It is rated moderate. Can be significant — usually manageable with 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.
From our Q&A
Real reader questions about these medications, each personally answered by our pharmacist:
Questions for your pharmacist
- Does my dose of Ketoconazole Topical or Oxybutynin 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 anything you'd monitor while I'm on both?
References (2)
- Product Information: DITROPAN(R) oral tablets, syrup, oxybutynin chloride oral tablets, syrup. Sanofi-Aventis US LLC, Kansan City, MO, 2008. DailyMed
- Product Information: DITROPAN XL(R) oral extended release tablets, oxybutynin chloride oral extended release tablets. Ortho-McNeil Pharmaceutical Inc, Raritan, NJ, 2008. DailyMed
Keep reading about Oxybutynin
Keep reading about Ketoconazole Topical
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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