Dofetilide and Ritonavir: Interaction Details
AI-assisted, pharmacist-reviewed · Source data updated Aug 8, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Ritonavir
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 dofetilide exposure and an increased risk of QT interval prolongation
Interaction Deep Dive
Coadministration of dofetilide with other drugs that may prolong the QT interval, such as ritonavir, is not recommended due to the potential for additive effects on the QT interval and increased risk of serious cardiovascular effects13. Concomitant use of dofetilide and ritonavir (CYP3A4 inhibitor) may also increase risk of QT interval prolongation 2.
Why it happens (mechanism)
Inhibition of CYP3A4-mediated metabolism of dofetilide; additive QT interval prolongation
Common questions
Can I take Dofetilide and Ritonavir together?
Increased dofetilide exposure 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 Ritonavir 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 Ritonavir 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 (3)
- Product Information: TIKOSYN(R) oral capsules, dofetilide oral capsules. Pfizer Labs (per FDA), New York, NY, 2019. DailyMed
- Product Information: Dofetilide oral capsules, dofetilide oral capsules. Granules Pharmaceuticals Inc. (per DailyMed), Chantilly, VA, 2025. DailyMed
- Product Information: NORVIR(R) oral tablets, oral solution, oral powder, ritonavir oral tablets, oral solution, oral powder. AbbVie Inc (per FDA), North Chicago, IL, 2020. DailyMed
Keep reading about Ritonavir
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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