Telaprevir and Ketoconazole Topical: Interaction Details
AI-assisted, pharmacist-reviewed · Source data updated Aug 8, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Telaprevir
No brand names on recordKetoconazole 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 ketoconazole exposure, an increased telaprevir exposure and an increased risk for QT interval prolongation
Interaction Deep Dive
Coadministration ketoconazole (a strong CYP3A4 inhibitor that may prolong the QT interval) with a CYP3A4 substrate known to prolong the QT interval, such as telaprevir is contraindicated, as it may result in elevated telaprevir exposure, increasing the risk for QT prolongation and life-threatening ventricular tachyarrhythmias, including torsades de pointes1. Coadministration of ketoconazole (CYP3A4 substrate) and telaprevir (strong CYP3A4 inhibitor) may also increase ketoconazole exposure. When coadministration is required, high doses of ketoconazole (greater than 200 mg/day) are not recommended 2.
Why it happens (mechanism)
Inhibition of CYP3A4-mediated metabolism of ketoconazole; inhibition of CYP3A4-mediated metabolism of telaprevir; additive QT interval prolongation
Literature reports
1 report — tap to read
a) In a pharmacokinetic study, following a single-dose of ketoconazole 400 mg given concomitantly with a single-dose of telaprevir 750 mg orally, mean ratio estimates of telaprevir AUC and Cmax were increased compared with administration of telaprevir alone (ratio estimates, 1.62; 90% confidence interval (CI), 1.45 to 1.81 and 1.24; 90% CI, 1.1 to 1.41, respectively). In addition, the mean ratio estimate of ketoconazole AUC was increased when a single ketoconazole 200 or 400 mg dose was given to patients receiving telaprevir 1250 mg every 8 hours for 4 days (ratio estimates, 2.25; 90% CI, 1.93 to 2.61 and 1.46; 90% CI, 1.35 to 1.58, respectively); corresponding mean ratio estimate of ketoconazole Cmax were 1.75 (90% CI, 1.51 to 2.03) and 1.23 (90% CI, 1.14 to 1.33), respectively). No changes were observed in the mean ratio estimate of Cmin for either ketoconazole or telaprevir 2.
Common questions
Can I take Telaprevir and Ketoconazole Topical together?
Increased ketoconazole exposure, an increased telaprevir exposure and an increased risk for QT interval prolongation Always confirm with your pharmacist or prescriber before making any change.
How serious is the Telaprevir and Ketoconazole Topical interaction?
It is rated contraindicated. These should generally not be used together.
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 Telaprevir 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: Ketoconazole oral tablet, ketoconazole oral tablet. Taro Pharmaceuticals U.S.A. Inc. (per DailyMed), Hawthorne, NY, 2024. DailyMed
- Product Information: INCIVEK(TM) film coated oral tablets, telaprevir film coated oral tablets. Vertex Pharmaceuticals Incorporated, Cambridge, MA, 2011.
Keep reading about Telaprevir
Keep reading about Ketoconazole Topical
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