Flecainide and Quinine: Interaction Details
AI-assisted, pharmacist-reviewed · Source data updated Aug 8, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Quinine
No brand names on recordFlecainide
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
Flecainide toxicity (cardiac arrhythmias)
Interaction Deep Dive
Quinine was found to interfere with the metabolism of flecainide. Studies of the metabolites of flecainide indicated that the first 2 metabolic steps were inhibited. Flecainide half-life increased by about 20%1.
Why it happens (mechanism)
Decreased hepatic metabolism
Literature reports
1 report — tap to read
a) Quinine was found to interfere with the metabolism of flecainide in healthy volunteers. Concomitant administration of quinine increased the AUC and half-life and decreased the total clearance of flecainide. In addition, the portion of flecainide excreted unchanged in the urine was significantly increased by quinine. Studies of the metabolites of flecainide indicated that the first 2 metabolic steps were inhibited 1.
Common questions
Can I take Flecainide and Quinine together?
Flecainide toxicity (cardiac arrhythmias) Always confirm with your pharmacist or prescriber before making any change.
How serious is the Flecainide and Quinine interaction?
It is rated minor. Usually limited clinical impact.
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 Flecainide or Quinine 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 anything you'd monitor while I'm on both?
References (1)
- Munafo A, Reymond-Michel G, & Biollaz J: Altered flecainide disposition in healthy volunteers taking quinine. Eur J Clin Pharmacol 1990; 38:269-273. PubMed
Keep reading about Quinine
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.
Check another combination
Our instant two-drug interaction checker is almost here.
Still have questions about this combination?
Every question gets a real answer from a licensed pharmacist — free, and usually within a day.
Ask the pharmacist