Drug Interaction Report

Flecainide and Propranolol: Interaction Details

A pharmacist-reviewed analysis of the Flecainide and Propranolol interaction: the documented clinical effects, severity rating, onset, mechanism, and management considerations, with cited references throughout.

AI-assisted, pharmacist-reviewed · Source data updated Aug 8, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature

Flecainide

Tambocor®
+

Propranolol

Hemangeol Inderal InnoPran
Dr. Brian Staiger, PharmD, BCPS
Medically reviewed by
Dr. Brian Staiger, PharmD, BCPS
Updated Aug 8, 2026
Editorial policy · Data sources
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Interaction severity
Moderate
Can be significant — usually manageable with monitoring.
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.

Of 300 documented Flecainide interactions, 11 are rated moderate — including this one.
Onset
delayed
Evidence
probable
Severity
Moderate

What happens

Bradycardia, decreased cardiac output

Interaction Deep Dive

A number of controlled studies have demonstrated that when propranolol and flecainide are taken together, the plasma levels of both drugs may increase by 15% to 30% (on the average), as compared to when either drug is used alone31.

Why it happens (mechanism)

Additive cardiovascular effects, decreased flecainide metabolism, decreased propranolol metabolism

Literature reports

2 reports — tap to read

a) Concomitant oral flecainide 200 mg twice daily and oral propranolol 80 mg three times daily therapy was reported to result in additive effects on decreasing the heart rate and lowering of systolic and diastolic blood pressure. Both drugs in combination produced less than additive effects on prolonging the PR interval. Echocardiographic changes were consistent with a negative inotropic effect, with propranolol more active than flecainide, and combined effects were either additive or less than additive 1.

b) A study reported the reversal of proarrhythmic events induced by encainide and flecainide with propranolol in 4 patients 2.

Common questions

Can I take Flecainide and Propranolol together?

Bradycardia, decreased cardiac output Always confirm with your pharmacist or prescriber before making any change.

How serious is the Flecainide and Propranolol interaction?

It is rated moderate. Can be significant — usually manageable with 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 "probable". Good supporting evidence, though not definitively proven.

Questions for your pharmacist

  • Does my dose of Flecainide or Propranolol 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 (3)

  1. Lewis GP & Holtzman JL: Interaction of flecainide with digoxin and propranolol. Am J Cardiol 1984; 53:52B-57B. PubMed
  2. Myerburg RJ, Kessler KM, Cox MM, et al: Reversal of proarrhythmic effects of flecainide acetate and encainide hydrochloride by propranolol. Circulation 1989; 80:1571-1579. DOI
  3. Holtzman JL, Kvam DC, Berry DA, et al: The pharmacodynamic and pharmacokinetic interaction of flecainide acetate with propranolol: effects on cardiac function and drug clearance. Eur J Clin Pharmacol 1987; 33:97-99. PubMed
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Flecainide

Keep reading about Flecainide

All Flecainide interactions (300) Flecainide drug information
Also serious with: Nirmatrelvir Mesoridazine Pimozide Mavorixafor
Propranolol

Keep reading about Propranolol

All Propranolol interactions (76) Propranolol drug information
Also serious with: Mefloquine Lacosamide Injection Capmatinib Indacaterol Oral Inhalation
Beyond drug–drug

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:

Flecainide + Activated Charcoal American Hellebore Arsenic Cesium Ephedra Grapefruit Sida Cordifolia 1,3-dmaa + 78 more
Propranolol + Activated Charcoal American Hellebore American Mistletoe Indian Snakeroot Tyramine 1,3-dmaa Acacia Rigidula Active Hexose Correlated Compound (ahcc) + 228 more

major · moderate · minor — check everything you take with our drug–supplement interaction checker.

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This information is for education, not a substitute for professional medical advice. Do not start, stop, or change any medication without talking to your pharmacist or prescriber.