Dofetilide and Ribociclib: Interaction Details
AI-assisted, pharmacist-reviewed · Source data updated Aug 8, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Ribociclib
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 CYP3A4 substrates exposure, an increased risk of CYP3A4 substrate-related adverse reactions and an increased risk of QT interval prolongation
Interaction Deep Dive
Avoid coadministration of ribociclib (a strong CYP3A4 inhibitor) with QT prolonging CYP3A4 substrates with NTI as it may increase CYP3A4 substrate exposure and adverse reactions, monitor for increased adverse reactions. The dose of a sensitive CYP3A4 substrate with NTI may need to be reduced. If unavoidable, monitor ECG when initiating, during concomitant use, and as clinically indicated. QTcF (QT interval corrected per Fridericia formula ) prolongation more than 480 ms and less than or equal to 500 ms requires interruption of ribociclib treatment until QTcF resolves to less than 480 ms. In early breast cancer, Interrupt ribociclib treatment and wait until QTcF resolves to less than 480 ms, and resume at the same dose, In advanced or metastatic breast cancer, Interrupt ribociclib treatment and wait until QTcF resolves to less than 480 ms, and reduce to the next lower dose level; if QTcF prolongation of more than 480 ms recurs, interrupt ribociclib treatment and wait until QTcF resolves to less than 480 ms, then resume at next lower dose level. When QTcF prolongation is more than 500 ms: Interrupt ribociclib treatment and wait until QTcF resolves to less than 480 ms, then resume at next lower dose level. If QTcF more than 500 ms recurs, discontinue ribociclib. Permanently discontinue ribociclib if QTcF interval prolongation is either more than 500 ms or more than 60 ms change from baseline and associated with any of the following: torsade de pointes, polymorphic ventricular tachycardia, syncope, or signs/symptoms of serious arrhythmia. If dose reduction below 200 mg/day is required, discontinue ribociclib1.
Why it happens (mechanism)
Inhibition of CYP3A4-mediated metabolism by ribociclib; additive QT interval prolongation
Literature reports
1 report — tap to read
a) Coadministration of ribociclib 400 mg once daily for 8 days with midazolam (a sensitive CYP3A4 substrate) increased midazolam Cmax by 2.1-fold and AUC(inf) by 3.8-fold in a drug interaction study in healthy subjects. Administration of ribociclib at 600 mg once daily is predicted to increase midazolam Cmax by 2.4-fold and AUC by 5.2-fold 1.
Common questions
Can I take Dofetilide and Ribociclib together?
Increased CYP3A4 substrates exposure, an increased risk of CYP3A4 substrate-related adverse reactions and an increased risk of QT interval prolongation Always confirm with your pharmacist or prescriber before making any change.
How serious is the Dofetilide and Ribociclib 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 Ribociclib 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: KISQALI(R) oral tablets, ribociclib oral tablets. Novartis Pharmaceuticals Corporation (per FDA), East Hanover, NJ, 2025. DailyMed
Keep reading about Ribociclib
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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