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 →
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.
How to Take It
Take flecainide exactly as your doctor tells you. For fast heart rates, the starting dose is usually 50 mg every 12 hours. Your doctor may increase the dose by 50 mg twice a day every four days until it works. The highest dose is 300 mg per day. For life-threatening ventricular arrhythmias, the starting dose is 100 mg every 12 hours, and your doctor may increase the dose by 50 mg twice a day every four days until it works. Do not take more than 400 mg per day.
This is a plain-language summary of flecainide's FDA labeling, not individualized dosing advice. Ask a pharmacist or prescriber before changing how you take this medication.
Pregnancy & Breastfeeding
Tell your doctor if you are pregnant or plan to become pregnant. It is not known if flecainide can harm an unborn baby. Talk to your doctor about the risks and benefits of taking flecainide while breastfeeding.
This is a plain-language summary of flecainide's FDA labeling, not individualized advice. Ask a pharmacist or prescriber about pregnancy or breastfeeding on this medication.
Missed Dose
If you miss a dose, take it as soon as you remember. If it is almost time for your next dose, skip the missed dose and continue with your regular schedule.
This is a plain-language summary of flecainide's FDA labeling, not individualized advice. Ask a pharmacist or prescriber what to do about your specific missed dose.
Storage
Store flecainide at room temperature (68º to 77ºF) in a tightly closed container, away from light.
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
- Irregular heartbeat in the upper chambers
Irregular heartbeat in the upper chambers
337 reports
- Feeling tired
Feeling tired
276 reports
- Difficulty breathing
Difficulty breathing
270 reports
- Feeling lightheaded
Feeling lightheaded
255 reports
- Feeling sick to your stomach
Feeling sick to your stomach
244 reports
- Pain in your head
Pain in your head
210 reports
- Loose, watery stools
Loose, watery stools
205 reports
- Weakness
Weakness
199 reports
- Accidentally losing your balance
Accidentally losing your balance
179 reports
- Medicine affecting another medicine
Medicine affecting another medicine
170 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.
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
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.
What to do: This combination must be avoided. Your doctor should prescribe a different medication that does not interact this way.
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.
What to do: Your doctor should use caution when prescribing these together. They may need to monitor your heart rhythm or adjust your medication dose.
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.
What to do: Use this combination with caution. Your doctor may need to monitor your heart rhythm or adjust your dosage.
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.
What to do: Your doctor should watch your heart health closely and may need to change your medication doses.
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.
What to do: Doctors generally do not recommend taking these two drugs at the same time because the risks are not yet clear.
This is a plain-language summary of interactions documented in FDA labeling, not individualized advice. Ask a pharmacist or prescriber before combining medications.
Common Questions
Can I take flecainide if I have a pacemaker?
Can I drink alcohol while taking flecainide?
Will flecainide cure my irregular heartbeat?
Can I stop taking flecainide if I feel better?
Does flecainide interact with other medications?
What should I do if I experience side effects?
How long does it take for flecainide to start working?
Can flecainide cause heart failure?
Is flecainide safe for children?
What do the numbers on the tablets mean?
What are the common side effects of flecainide?
Does flecainide interact with other medications?
What drug class is flecainide?
Is flecainide safe during pregnancy?
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 →
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
Why some drugs demand precise dosing and monitoring
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 further shape supply and switching decisions. This page summarizes public FDA data for educational purposes only and is not a substitute for professional medical advice, always consult a licensed healthcare provider before starting, stopping, or changing any medication.
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. Always consult a healthcare professional before making medication decisions.
Last updated: January 9, 2024
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 and last refreshed May 2026. See our methodology for per-source dates and refresh cadence. Spot a figure that looks wrong? Report a correction.
All federal data sources used on this page
- FDA Orange Book - approved drug products with therapeutic equivalence. accessdata.fda.gov/cder/ob
- FDA DailyMed - NIH-hosted drug labeling for FDA-approved meds. dailymed.nlm.nih.gov
- FDA Adverse Event Reporting System (FAERS) - post-marketing safety surveillance. fda.gov/drugs/faers
- NLM RxNorm - standardized clinical drug nomenclature. nlm.nih.gov/research/umls/rxnorm
- CMS Medicare Part B Drug Average Sales Price Files - federal drug pricing data. cms.gov/medicare/part-b-drugs/asp
- FDA Drug Shortages Database - current and resolved drug shortage tracking. accessdata.fda.gov/drugshortages