Darifenacin and Flecainide: Interaction Details
AI-assisted, pharmacist-reviewed · Source data updated Aug 8, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Darifenacin
Flecainide
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 flecainide exposure with an increased risk of cardiac arrhythmias
Interaction Deep Dive
Coadministered darifenacin may increase flecainide exposure, causing a potential risk of arrhythmias or other serious adverse effects. Flecainide, like imipramine, is metabolized primarily by the CYP2D6 isoenzyme and it has a narrow therapeutic window. The mean maximum concentration (Cmax) and area under the concentration-time curve (AUC) of imipramine increased 57% and 70%, respectively, when used together with darifenacin 30 mg once daily at steady-state. Note: The recommended dose of darifenacin is 7.5 or 15 mg once daily. The AUC of desipramine, the active metabolite of imipramine, increased 3.6-fold. Caution should be used with the coadministration of darifenacin and CYP2D6 substrates with a narrow therapeutic window, such as flecainide1.
Why it happens (mechanism)
Competitive inhibition of CYP2D6-mediated flecainide metabolism
Common questions
Can I take Darifenacin and Flecainide together?
Increased flecainide exposure with an increased risk of cardiac arrhythmias Always confirm with your pharmacist or prescriber before making any change.
How serious is the Darifenacin and Flecainide interaction?
It is rated major. Potentially serious — often needs a change or close monitoring.
How quickly could this interaction happen?
The documented onset is "delayed". Effects tend to build up gradually over days to weeks.
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 Darifenacin or Flecainide 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: Enablex, darifenacin. Pfizer Inc. Brooklyn, New york, USA, 2004. DailyMed
Keep reading about Darifenacin
Keep reading about Flecainide
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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