Dofetilide and Clarithromycin: Interaction Details
AI-assisted, pharmacist-reviewed · Source data updated Aug 8, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Clarithromycin
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, increased risk of QT interval prolongation and torsade de pointes
Interaction Deep Dive
Prolongation of the QT interval and torsade de pointes (including fatalities) have been reported following administration of clarithromycin. Concomitant therapy with clarithromycin and dofetilide (QT prolonging class III antiarrhythmic agents and a CYP3A4 substrate) should be avoided due to the increased risk of dofetilide exposure resulting in serious cardiac adverse events including QT prolongation and torsade de pointes. Elderly patients may be more susceptible to medication-related changes in the QT interval2. Specific antiarrhythmic agents may require a washout period before starting another QT-prolonging agent. Dofetilide, for example, should be stopped for at least 2 days before initiating any interacting drug 1.
Why it happens (mechanism)
Inhibition of CYP3A4-substrate metabolism by clarithromycin; additive QT interval prolongation
Literature reports
1 report — tap to read
a) Concurrent use of class III antiarrhythmic agents, and other drugs that can prolong the QT interval, such as clarithromycin, is not recommended. Dofetilide should be stopped for at least 2 days before any interacting drug is initiated. If concurrent use cannot be avoided, cautious dosing and telemetric monitoring is advised 1.
Common questions
Can I take Dofetilide and Clarithromycin together?
Increased dofetilide exposure, increased risk of QT interval prolongation and torsade de pointes Always confirm with your pharmacist or prescriber before making any change.
How serious is the Dofetilide and Clarithromycin 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 Clarithromycin 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)
- Yamreudeewong W, DeBisschop M, Martin LG, et al: Potentially significant drug interactions of class III antiarrhythmic drugs. Drug Safety 2003; 26(6):421-438. PubMed
- Product Information: VOQUEZNA(TM) TRIPLE PAK(TM) oral kit, vonoprazan oral tablets, amoxicillin oral capsules, clarithromycin oral tablets kit. Phathom Pharmaceuticals (per FDA), Buffalo Grove, IL, 2023. DailyMed
Keep reading about Clarithromycin
Keep reading about Dofetilide
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Prescription drugs aren't the whole picture — herbal and dietary supplements can interact with them too. From the evidence-graded Natural Medicines database:
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