Drug Interaction Report

Sodium Bicarbonate and Flecainide: Interaction Details

Name: Sodium Bicarbonate and Flecainide Interaction
Creator: Dr. Brian Staiger, PharmD, BCPS

A pharmacist-reviewed analysis of the Sodium Bicarbonate and Flecainide 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®

Sodium Bicarbonate

Alka-Seltzer® Heartburn Desempacho Neut brand of sodium bicarbonate

Medically reviewed by

Dr. Brian Staiger, PharmD, BCPS

Updated Aug 8, 2026

Editorial policy · Data sources

Interaction severity

Moderate

Can be significant — usually manageable with monitoring.

Minor

Moderate

Major

Contraindicated

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 26 documented Sodium Bicarbonate interactions, 12 are rated moderate — including this one.

Onset

delayed

Evidence

theoretical

Severity

Moderate

What happens

Flecainide toxicity (cardiac arrhythmias)

Interaction Deep Dive

Urinary alkalinization decreases flecainide renal excretion. The half-life, when urinary pH is not controlled, is 14 hours compared to 18 to 30 hours with alkaline urine. Monitor urinary pH if this interaction is expected and flecainide plasma level¹².

Why it happens (mechanism)

Increased tubular reabsorption

Common questions

Can I take Sodium Bicarbonate and Flecainide together?

Flecainide toxicity (cardiac arrhythmias) Always confirm with your pharmacist or prescriber before making any change.

How serious is the Sodium Bicarbonate and Flecainide 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 "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 Sodium Bicarbonate 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 anything you'd monitor while I'm on both?

References (2)

Nappi JM & Anderson JL: Flecainide: a new prototype antiarrhythmic agent. Pharmacotherapy 1985; 5:209-221. PubMed
Johnston A, Warrington S, & Turner P: Flecainide pharmacokinetics in healthy volunteers: the influence of urinary pH. Br J Clin Pharmacol 1985; 20:333-338. PubMed

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Flecainide

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All Flecainide interactions (300) Flecainide drug information

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Sodium Bicarbonate

Keep reading about Sodium Bicarbonate

All Sodium Bicarbonate interactions (26) Sodium Bicarbonate drug information

Also serious with: Gefitinib Memantine Octreotide Injection Neratinib

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

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

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A message from HelloPharmacist

About our interaction database: depth, not breadth

HelloPharmacist doesn't license one of the big commercial interaction databases, so what you'll find here is not a complete list of every known drug interaction. Instead, each entry is researched, analyzed, and written up individually — documented from the published literature, reviewed by a pharmacist, and cited so you can check every source yourself.

If a combination isn't listed here, it means we haven't documented it yet — never that it's safe. For screening a full medication list, we recommend pairing this site with a comprehensive tool like the Drugs.com Interaction Checker and, most importantly, a review by your own pharmacist. For a deep, plain-English, fully sourced explanation of a specific documented interaction — that's exactly what we built this for.

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.