Thiotepa and Ketoconazole Topical: Interaction Details
AI-assisted, pharmacist-reviewed · Source data updated Aug 8, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Ketoconazole Topical
Thiotepa
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 thiotepa exposure and an increased risk of thiotepa-related adverse effects and toxicity
Interaction Deep Dive
Avoid concomitant use of thiotepa (CYP3A4 substrate) and a strong CYP3A4 inhibitor due to increased risk of thiotepa exposure and the potential effects on efficacy. Consider alternative medication with no or minimal CYP3A4 inhibition. If concomitant use cannot be avoided, monitor the patient closely for adverse drug reaction12.
Why it happens (mechanism)
Inhibition of CYP3A4 mediated metabolism of thiotepa
Common questions
Can I take Thiotepa and Ketoconazole Topical together?
Increased thiotepa exposure and an increased risk of thiotepa-related adverse effects and toxicity Always confirm with your pharmacist or prescriber before making any change.
How serious is the Thiotepa 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 Thiotepa 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)
- Product Information: TEPADINA(R) intravenous, intracavitary, intravesical injection, thiotepa intravenous, intracavitary, intravesical injection. ADIENNE SA (per FDA), Cedar Park, TX, 2017. DailyMed
- Product Information: TEPYLUTE intravenous injection, thiotepa intravenous injection. Shorla Oncology Inc (per FDA), Cambridge, MA, 2024. DailyMed
Keep reading about Ketoconazole Topical
Keep reading about Thiotepa
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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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