Dofetilide and Ivacaftor: Interaction Details
AI-assisted, pharmacist-reviewed · Source data updated Aug 8, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Ivacaftor
Dofetilide
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 CYP3A substrate exposure
Interaction Deep Dive
Use caution with coadministration of ivacaftor or ivacaftor-containing products and a CYP3A substrate with a narrow therapeutic index (including cycloSPORINE, everolimus, sirolimus, and tacrolimus), as this may increase or prolong the therapeutic effect and adverse reactions of the CYP3A substrate. If coadministration is required, monitor appropriately1.
Why it happens (mechanism)
Inhibition of CYP3A-substrate metabolism by ivacaftor
Literature reports
1 report — tap to read
a) Coadministration of ivacaftor with the sensitive CYP3A substrate midazolam increased the midazolam exposure by 1.5-fold. Coadministration of ivacaftor with the sensitive P-gp substrate digoxin increased the digoxin exposure by 1.3-fold 1.
Common questions
Can I take Dofetilide and Ivacaftor together?
Increased CYP3A substrate exposure Always confirm with your pharmacist or prescriber before making any change.
How serious is the Dofetilide and Ivacaftor 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.
From our Q&A
Real reader questions about these medications, each personally answered by our pharmacist:
Questions for your pharmacist
- Does my dose of Dofetilide or Ivacaftor 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: KALYDECO(R) oral tablets, oral granules, ivacaftor oral tablets, oral granules. Vertex Pharmaceuticals Incorporated (per FDA), Boston, MA, 2023. DailyMed
Keep reading about Ivacaftor
Keep reading about Dofetilide
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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