Prescription medication · Class IC Antiarrhythmic

flecainide

Also sold as Tambocor. This medicine can prevent fast heart rates in the upper chambers of the heart.

Data updated 2026-05-15

2,345
FDA reports
22
InteractionsSeveral interactions
$0.16
Generic price (NADAC)

What the data shows

flecainide (Tambocor) is a prescription Class IC Antiarrhythmic, with 2,345 FDA adverse-event reports on file, with 22 documented drug interactions.

Reporting volume reflects how widely a drug is used and studied, not how dangerous it is, a FAERS report documents a temporal association, never proof of cause.

flecainide (Tambocor) is a prescription Class IC Antiarrhythmic. This medicine can prevent fast heart rates in the upper chambers of the heart.

Flecainide is a medicine used to prevent irregular heartbeats. It helps your heart beat normally.

Verify with FDA → · CMS NADAC pricing →

Drug Pricing (NADAC)

Generic Price

$0.16/unit

Generic Available

Yes (7 manufacturers)

Pricing data from NADAC (CMS), effective December 18, 2024. Compare all drug costs →

NADAC price trail: FLECAINIDE ACETATE 100 MG TAB

Same CMS presentation as the headline generic unit price above (2 effective dates). Adjacent % compares consecutive NADAC releases for this description only, not a patient out-of-pocket quote. Latest step: +4.9% vs prior release.

Effective NADAC / unit vs prior NDCs
May 22, 2024 $0.1547/EA - 1
December 18, 2024 $0.1623/EA +4.9% 12
View Alternatives → Compare with Another Drug →

What it does

This medicine can prevent fast heart rates in the upper chambers of the heart.

Common side effects

Dizziness, Vision problems, Difficulty breathing

Key warnings

Flecainide can increase the risk of death or cardiac arrest in some patients who have had a heart attack.

The sections below are summarized in plain English from flecainide's FDA-approved prescribing information. They describe what the official label says, and are not personal medical advice.

How It Works

Flecainide works by slowing down electrical signals in the heart. This helps to stabilize your heart rhythm. It belongs to a class of drugs called Class IC antiarrhythmics.

Side Effects (from patient reports)

Based on 2,345 FDA adverse event reports.

Most-reported reactions

Adverse reactions in FAERS for flecainide, by number of reports

reports

What this shows Bars show how often each reaction was reported, not how likely it is to happen, a report records a temporal association, never proof that the drug caused it.

Source FDA Adverse Event Reporting System (FAERS)

Serious Warnings

Flecainide can increase the risk of death or cardiac arrest in some patients who have had a heart attack. It is generally not recommended for people with less serious, but unpleasant, heart rhythm problems. Flecainide is also not recommended if you have chronic atrial fibrillation.

Known Drug Interactions

major nirmatrelvir/ritonavir

Antiarrhythmics amiodarone, dronedarone, flecainide, propafenone, quinidine ↑ antiarrhythmic Co-administration contraindicated due to potential for cardiac arrhythmias [see Contraindications (4) ] .

Mechanism: Ritonavir blocks the enzymes that process flecainide, leading to much higher levels of the heart drug in your system. This increase can cause the heart to beat in an unsafe or irregular way.

moderate darifenacin

7 DRUG INTERACTIONS Caution should be taken when darifenacin extended-release tablets are used concomitantly with medications that are predominantly metabolized by CYP2D6 and which have a narrow therapeutic window, such as flecainide, thioridazine and tricyclic antidepressants ( 7.2 ) The concomitant use of darifenacin extended-release tablets with other anticholinergic agents may increase the frequency and/or severity of dry mouth, constipation, blurred vision and other anticholinergic pharmacological effects. 7.3 CYP2D6 Substrates Caution should be taken when darifenacin extended-release...

Mechanism: Darifenacin interferes with the enzyme that clears flecainide from your system. This can cause the heart medicine to reach high levels in your body that could be toxic.

moderate fluoxetine

Coadministration of fluoxetine with other drugs that are metabolized by CYP2D6, including certain antidepressants (e.g., TCAs), antipsychotics (e.g., phenothiazines and most atypicals), and antiarrhythmics (e.g., propafenone, flecainide, and others) should be approached with caution. Drugs with a narrow therapeutic index represent the greatest concern (e.g., flecainide, propafenone, vinblastine, and TCAs).

Mechanism: Fluoxetine blocks the enzyme that breaks down flecainide in your body. This can cause flecainide to build up to unsafe levels in your blood.

minor propranolol

In a study involving healthy subjects receiving flecainide acetate and propranolol concurrently, plasma flecainide levels were increased about 20% and propranolol levels were increased about 30% compared to control values. In this formal interaction study, flecainide acetate and propranolol were each found to have negative inotropic effects; when the drugs were administered together, the effects were additive. The effects of concomitant administration of flecainide acetate and propranolol on the PR interval were less than additive.

Mechanism: Taking these drugs together increases the amount of medicine in your blood and can further weaken the heart's ability to pump.

minor diltiazem

There has been too little experience with the coadministration of flecainide acetate with nifedipine or diltiazem to recommend concomitant use.

Mechanism: There is not enough medical information available to know how these two drugs interact when used together.

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This is a plain-language summary of FDA-label interaction records and does not provide individual medication-combination directions.

Common Questions

Can I take flecainide if I have a pacemaker?
Flecainide is contraindicated in patients with preexisting second- or third-degree AV block, or with right bundle branch block when associated with a left hemiblock (bifascicular block), unless a pacemaker is present.
Can I drink alcohol while taking flecainide?
Ask your doctor or pharmacist. They can give you the best advice based on your health and other medicines.
Will flecainide cure my irregular heartbeat?
Flecainide helps to control irregular heartbeats, but it may not cure them. You may need to take it long-term.
Can I stop taking flecainide if I feel better?
Do not stop taking flecainide without talking to your doctor first. Stopping suddenly can make your condition worse.
Does flecainide interact with other medications?
Yes, flecainide can interact with other medications. Tell your doctor about all the medicines you take, including over-the-counter drugs and supplements.
What should I do if I experience side effects?
Tell your doctor if you experience any side effects while taking flecainide. They may be able to adjust your dose or recommend other treatments.
How long does it take for flecainide to start working?
It may take several days for flecainide to reach its full effect. Your doctor will monitor your heart rhythm to see how well it is working.
Can flecainide cause heart failure?
Flecainide can worsen heart failure in some patients. Tell your doctor if you have a history of heart failure.
Is flecainide safe for children?
Any use of flecainide acetate tablets in children should be directly supervised by a cardiologist skilled in the treatment of arrhythmias in children.
What do the numbers on the tablets mean?
Flecainide Acetate Tablets USP, 50 mg are debossed with “CC” on one side and “11” on other side. 100 mg are debossed with ‘1’ and ‘2’ separated by deep score line on one side and “CC” on other side. 150 mg are debossed with ‘1’ and ‘3’ separated by deep score line on one side and “CC” on other side.
What are the common side effects of flecainide?
The registry lists Dizziness, Vision problems, Difficulty breathing, Headache, Nausea among the most-reported FAERS reaction terms for flecainide. The compiled record contains 2,345 FDA adverse-event reports. These counts are not an individual symptom assessment.
Does flecainide interact with other medications?
The registry has 22 documented interaction rows for flecainide. Notable source-record pairings include nirmatrelvir/ritonavir, darifenacin, fluoxetine. These rows are not a complete medication review.
What drug class is flecainide?
flecainide belongs to the Class IC Antiarrhythmic drug class. It requires a prescription (Rx). This medicine can prevent fast heart rates in the upper chambers of the heart.
What pregnancy or breastfeeding source fields are listed for flecainide?
The FDA label for flecainide contains product-specific pregnancy or breastfeeding language. PlainMeds does not apply that source text to an individual.

Related Medications in Class IC Antiarrhythmic

Other drugs grouped near flecainide - same-class peers and common alternatives.

adenosine

Adenocard

Adenosine (Adenocard) is a medicine used to treat certain types of irregular heartbeats.

Compare with flecainide →

amiodarone

Cordarone, Pacerone

Amiodarone (Pacerone) is a medicine used to treat life-threatening, irregular heartbeats.

Compare with flecainide →

atropine

AtroPen

Atropine is a medicine that can temporarily block severe effects on your body.

Compare with flecainide →

bumetanide

Bumex

Bumetanide is a water pill (diuretic).

Compare with flecainide →

carvedilol

Coreg

Carvedilol is a medicine that lowers blood pressure and helps your heart work better.

Compare with flecainide →

Compare flecainide vs adenosine side-by-side →

Medication Guides

Understanding Drug Interactions

How CYP450 enzymes, inhibitors, and inducers affect your medications

Generic vs Brand Name Drugs

FDA requirements, cost savings, and when the difference matters

Narrow Therapeutic Index Drugs

FDA bioequivalence and label-record context for narrow therapeutic index medicines

Common Drug Interactions

Dangerous medication combinations and how to protect yourself

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What the FDA Data Shows for flecainide

The FDA label for flecainide (sold under brand names such as Tambocor) classifies it as a prescription-only medication in the Class IC Antiarrhythmic class. This medicine can prevent fast heart rates in the upper chambers of the heart. Official labeling lists 8 commonly reported side effects, including Dizziness, Vision problems, Difficulty breathing.

Post-market surveillance from the FDA Adverse Event Reporting System (FAERS) captures real-world experience. For this drug, FAERS contains 2,345 voluntary reports. The database also lists 22 documented drug interactions derived from FDA labeling, with the top-flagged interaction rated major severity. NADAC pricing from CMS shows a generic unit cost of $0.16.

Report counts do not establish causation, a FAERS entry documents a temporal association, not proof that the drug produced the outcome. Widely prescribed medications naturally accumulate more reports than niche therapies, so raw totals must be interpreted alongside total exposure. Shortage status, recall history, and patent information are separate source-record fields. This page is a public FDA/CMS registry and does not provide medical, treatment, substitution, or medication-change directions.

Data Sources

Drug labeling: FDA Drug Labels (SPL/DailyMed). Adverse events: FDA Adverse Event Reporting System (FAERS). Pricing: CMS National Average Drug Acquisition Cost (NADAC).

FAERS reports are voluntary and do not establish causation. Drug interactions are derived from FDA labeling and clinical references. This registry does not provide medication decisions.

Last updated: January 9, 2024

PlainMeds is rendered directly from FDA openFDA/FAERS extracts, DailyMed labels, and CMS drug-pricing files, no number is typed in by an editor. FAERS counts, recalls, shortages, and price figures on this page are queried live from those federal extracts. See our editorial standards & corrections policy, the methodology behind these numbers, or report a data error. Data current as of 2026-05-15. Primary sources: openFDA / FAERS, DailyMed and CMS Part B ASP.

Read our methodology - how this data is sourced, computed, and verified.

Data currency: FDA FAERS adverse-event reports through 2025, CMS NADAC acquisition-cost pricing effective December 2024, compiled from the source snapshot dated . See our methodology for per-source dates and refresh cadence. Spot a figure that looks wrong? Report a data issue.

All federal data sources used on this page