Reviewed on 9/1/2021

What Is Flecainide and How Does It Work?

Flecainide is a prescription medication used to treat paroxysmal supraventricular tachycardias (PSVT), including atrioventricular nodal reentrant tachycardia, atrioventricular reentrant tachycardia and other supraventricular tachycardias of unspecified mechanism associated with disabling symptoms, paroxysmal atrial fibrillation/flutter (PAF) associated with disabling symptoms and documented ventricular arrhythmias, such as sustained ventricular tachycardia (sustained VT), that in the judgment of the physician are life-threatening.

  • Flecainide is available under the following different brand names: Tambocor.

What Are Dosages of Flecainide?

Dosages of Flecainide:

Adult and Pediatric Dosages


  • 50 mg
  • 100 mg
  • 150 mg

Dosage Considerations – Should be Given as Follows:


Adult Dosages

  • PSVT and paroxysmal atrial fibrillation
  • 50 mg orally twice daily; may increase by 50 mg every 4 days; do not exceed 300 mg/day
  • Sustained VT
  • 100 mg orally twice daily initiated in hospital; may increase by 50 mg every 4 days; do not exceed 400 mg/day

Pediatric Dosages

  • Infants under 6 months: 50 mg/m²/day orally divided every 8-12 hours
  • Infants 6 months or older: 100 mg/m²/day orally divided every 8-12 hours
  • Not to exceed 200 mg/m²/day

Dosing considerations

Adults and Pediatric Dosages:

  • Pediatric only: Usual therapeutic level: 200-500 ng/ml; some may require under 800 ng/ml for adequate control
  • Steady-state plasma levels not achieved for 3-5 days, so increases in dosage should not be made less than every 4 days
  • Loading dose not recommended, due to increased incidence of proarrhythmic events and chronic heart failure
  • Patients intolerant to twice-daily dosing may require 8 hour dosing
  • Once adequate control of arrhythmia has been achieved, may reduce dose, provided there is no loss of efficacy
  • After 5 doses/steady-state, obtain ECG after initiation or change of dose; obtain plasma trough flecainide levels 1 hour pre-dose
  • Usual trough plasma levels: 0.2-1 mcg/mL
  • When given concomitantly with amiodarone, reduce flecainide dose by 50% and monitor closely
  • Dose cautiously in patients with history of heart attach (myocardial infarction) or chronic heart failure
  • When switching from another antiarrhythmic to flecainide, allow over 2-4 plasma half-lives to elapse before starting flecainide; if discontinuation of previous drug may produce life-threatening arrhythmias, consider hospitalizing patient

Dosage Modifications

Adult and Pediatric Dosages:

Renal impairment

  • Severe (under 35 ml/min): 100 mg orally once daily or 50 mg orally twice daily
  • Higher than 25 ml/min: 100 mg orally twice daily

Hepatic impairment

  • Use only if benefits outweigh risk; monitor plasma levels regularly; reduce dose as necessary


Heart Disease: Symptoms, Signs, and Causes See Slideshow

What Are Side Effects Associated with Using Flecainide?

Side effects of flecainide include:

This document does not contain all possible side effects and others may occur. Check with your physician for additional information about side effects.

What Other Drugs Interact with Flecainide?

If your doctor has directed you to use this medication, your doctor or pharmacist may already be aware of any possible drug interactions and may be monitoring you for them. Do not start, stop, or change the dosage of any medicine before checking with your doctor, health care provider, or pharmacist first.

  • Severe interactions of flecainide include:
    • tipranavir
  • Flecainide has serious interactions with at least 29 different drugs.
  • Flecainide has moderate interactions with at least 128 different drugs.
  • Mild interactions of flecainide include:

This information does not contain all possible interactions or adverse effects. Therefore, before using this product, tell your doctor or pharmacist of all the products you use. Keep a list of all your medications with you, and share this information with your doctor and pharmacist. Check with your health care professional or doctor for additional medical advice, or if you have health questions, concerns, or for more information about this medicine.

What Are Warnings and Precautions for Flecainide?



  • National Heart, Lung, and Blood Institute (NHLBI) Cardiac Arrhythmia Suppression Trial (CAST): Excessive mortality or nonfatal cardiac arrest (7.7%) shown with encainide or flecainide, compared with placebo (3%)
  • This was a long-term, multicenter, randomized, double-blind study in patients with asymptomatic, non-life-threatening ventricular arrhythmias who previously had a heart attack (myocardial infarction) over 6 days prior but less than

2 years

  • The average duration of treatment with encainide or flecainide was 10 months
  • Applicability of results to other populations is uncertain
  • Reserve class IC antiarrhythmics use for life-threatening ventricular arrhythmias only
  • Due to known proarrhythmic properties of flecainide and lack of evidence of improved survival for any antiarrhythmics, flecainide use should be restricted to patients with life-threatening ventricular arrhythmias

Ventricular proarrhythmic effects with atrial flutter

  • Not recommended for chronic atrial fibrillation
  • 10.5% incidence of ventricular tachycardia/fibrillation in patients treated for chronic atrial fibrillation
  • Proarrhythmic effects with flecainide for atrial fibrillation/flutter: Increased risk of PVCs, ventricular tachycardia, ventricular fibrillation, and fatality
  • As with other class I agents, the use of flecainide for atrial flutter has been reported with 1:1 atrioventricular conduction due to atrial rate slowing
  • Paradoxical increase in ventricular rate may occur in patients with atrial fibrillation; concomitant negative chronotropic therapy (digoxin, beta-blockers) may lower the risk
  • This medication contains flecainide. Do not take Tambocor if you are allergic to flecainide or any ingredients contained in this drug.
  • Keep out of reach of children. In case of overdose, get medical help or contact a Poison Control Center immediately


  • Hypersensitivity
  • 2nd or 3rd-degree atrioventricular block, right bundle branch block when associated with left hemiblock (bifascicular block), unless a pacemaker is present to sustain cardiac rhythm; discontinue therapy immediately

Effects of Drug Abuse

  • No information available

Short-Term Effects

  • See "What Are Side Effects Associated with Using Flecainide?"

Long-Term Effects

  • See "What Are Side Effects Associated with Using Flecainide?"


  • Atrial fibrillation, chronic heart failure, low blood pressure, high blood pressure, post-heart attack (myocardial infarction) patients, geriatrics, arrhythmia events, liver/kidney impairment, sick sinus syndrome
  • May slow cardiac conduction to produce dose-related increases in PR, QRS, and QT intervals; manage the patient on the lowest effective dose
  • Discontinuation should be done in a hospital
  • Causes increased mortality in post-acute myocardial infarction (AMI) period, also with chronic atrial fibrillation
  • May affect endocardial pacemaker reversibly by increasing endocardial pacing thresholds or suppressing ventricular escape rhythms; do not administer to patients with existing poor thresholds or nonprogrammable pacemakers unless suitable pacing rescue is available
  • Correct preexisting low potassium or high potassium before initiating therapy
  • May cause visual disturbances
  • Flecainide may depress LV systolic function significantly with preexisting LV systolic dysfunction
  • Flecainide should be avoided in patients with heart failure or structural heart disease

Pregnancy and Lactation

  • Use flecainide during pregnancy with caution if the benefits outweigh the risks. Animal studies show risk and human studies are not available, or neither animal nor human studies were done.
  • Flecainide enters breast milk. Consult with your physician if breastfeeding


See Images
Medscape. Flecainide.
RxList. Tambocor Monograph.

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