Ketoconazole Topical and Trimetrexate: Interaction Details
AI-assisted, pharmacist-reviewed · Source data updated Aug 8, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Ketoconazole Topical
Trimetrexate
No brand names on record
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 trimetrexate exposure and an increased trimetrexate-related adverse reactions
Interaction Deep Dive
Caution is advised when trimetrexate and ketoconazole are coadministered, as this may trimetrexate exposure. Upon coadministration, monitor patients closely for signs or symptoms of increased or prolonged effects or side effects of the trimetrexate, and reduce trimetrexate dosage as deemed necessary1.
Why it happens (mechanism)
Unknown
Common questions
Can I take Ketoconazole Topical and Trimetrexate together?
Increased trimetrexate exposure and an increased trimetrexate-related adverse reactions Always confirm with your pharmacist or prescriber before making any change.
How serious is the Ketoconazole Topical and Trimetrexate interaction?
It is rated major. Potentially serious — often needs a change or close monitoring.
How quickly could this interaction happen?
The documented onset is "delayed". Effects tend to build up gradually over days to weeks.
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 Ketoconazole Topical or Trimetrexate 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)
- Product Information: Ketoconazole oral tablet, ketoconazole oral tablet. Taro Pharmaceuticals U.S.A. Inc. (per DailyMed), Hawthorne, NY, 2024. DailyMed
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