Ketoconazole Topical and Vanzacaftor: Interaction Details
AI-assisted, pharmacist-reviewed · Source data updated Aug 8, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Ketoconazole Topical
Vanzacaftor
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 vanzacaftor exposure and an increased risk of vanzacaftor-related adverse reactions
Interaction Deep Dive
Coadministration of vanzacaftor and a strong CYP3A inhibitor may increase the exposure of vanzacaftor, which may increase the risk of vanzacaftor-associated adverse reactions. In a drug interaction study, coadministration of a single dose of vanzacaftor 5 mg with the strong CYP3A inhibitor itraconazole 200 mg daily increased vanzacaftor AUC by 6.37-fold and Cmax by 1.55-fold. Reduce the vanzacaftor dosage with concomitant use of strong CYP3A inhibitors. For 6 to less than 12 years old, patients weighing less than 40 kg adjust the dose to two tablets of vanzacaftor 4 mg/tezacaftor 20 mg/deutivacaftor 50 mg once a week and for patients greater than or equal to 40 kg adjust the dose to one tablet of vanzacaftor 10 mg/tezacaftor 50 mg/deutivacaftor 125 mg once a week. For 12 years and older patients adjust the dose to one tablet of vanzacaftor 10 mg/tezacaftor 50 mg/deutivacaftor 125 mg once a week1.
Why it happens (mechanism)
Inhibition of CYP3A-mediated metabolism of vanzacaftor
Literature reports
1 report — tap to read
a) In a drug interaction study, coadministration of a single dose of vanzacaftor 5 mg with the strong CYP3A inhibitor itraconazole 200 mg daily increased vanzacaftor AUC by 6.37-fold and Cmax by 1.55-fold 1.
Common questions
Can I take Ketoconazole Topical and Vanzacaftor together?
Increased vanzacaftor exposure and an increased risk of vanzacaftor-related adverse reactions Always confirm with your pharmacist or prescriber before making any change.
How serious is the Ketoconazole Topical and Vanzacaftor 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 "probable". Good supporting evidence, though not definitively proven.
Questions for your pharmacist
- Does my dose of Ketoconazole Topical or Vanzacaftor 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: ALYFTREK(R) oral tablets, vanzacaftor, tezacaftor, and deutivacaftor oral tablets. Vertex Pharmaceuticals Incorporated (per FDA), Boston, MA, 2024. DailyMed
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