Last reviewed 2026-04-20 · How we verify

Tambocor (FLECAINIDE)

Flecainide (Tambocor) is a marketed antiarrhythmic drug primarily indicated for the treatment of Paroxysmal Supraventricular Tachycardias (PSVT). Its key strength lies in its mechanism of action, which effectively blocks potassium channels in the heart to regulate rhythm, setting it apart in the class. The primary risk is the upcoming key composition patent expiry in 2028, which could lead to increased competition from generics.

At a glance

Approved indications

• Paroxysmal Supraventricular Tachycardias (PSVT)
• Paroxysmal Atrial Fibrillation/Flutter (PAF)
• Documented Ventricular Arrhythmias

Boxed warnings

• WARNINGS Mortality Flecainide acetate was included in the National Heart Lung and Blood Institute's Cardiac Arrhythmia Suppression Trial (CAST), a long-term, multicenter, randomized, double-blind study in patients with asymptomatic non-life-threatening ventricular arrhythmias who had a myocardial infarction more than six days but less than two years previously. An excessive mortality or non-fatal cardiac arrest rate was seen in patients treated with flecainide acetate compared with that seen in patients assigned to a carefully matched placebo-treated group. This rate was 16/315 (5.1%) for flecainide acetate and 7/309 (2.3%) for the matched placebo. The average duration of treatment with flecainide acetate in this study was ten months. The applicability of the CAST results to other populations (e.g., those without recent myocardial infarction) is uncertain, but at present, it is prudent to consider the risks of Class IC agents (including flecainide acetate), coupled with the lack of any evidence of improved survival, generally unacceptable in patients without life-threatening ventricular arrhythmias, even if the patients are experiencing unpleasant, but not life-threatening, symptoms or signs. Ventricular Pro-arrhythmic Effects in Patients with Atrial Fibrillation/Flutter A review of the world literature revealed reports of 568 patients treated with oral flecainide acetate for paroxysmal atrial fibrillation/flutter (PAF). Ventricular tachycardia was experienced in 0.4% (2/568) of these patients. Of 19 patients in the literature with chronic atrial fibrillation (CAF), 10.5% (2) experienced VT or VF. FLECAINIDE IS NOT RECOMMENDED FOR USE IN PATIENTS WITH CHRONIC ATRIAL FIBRILLATION. Case reports of ventricular proarrhythmic effects in patients treated with flecainide acetate for atrial fibrillation/flutter have included increased PVCs, VT, ventricular fibrillation (VF), and death. As with other Class I agents, patients treated with flecainide acetate for atrial flutter have been reported with 1:1 atrioventricular conduction due to slowing the atrial rate. A paradoxical increase in the ventricular rate also may occur in patients with atrial fibrillation who receive flecainide acetate. Concomitant negative chronotropic therapy such as digoxin or beta-blockers may lower the risk of this complication.

Common side effects

• Dizziness
• Visual Disturbances
• Dyspnea
• Headache
• Nausea
• Fatigue
• Palpitation
• Chest Pain
• Asthenia
• Tremor
• Constipation
• Edema

Drug interactions

• digitalis preparations
• propranolol
• beta blockers
• highly protein-bound drugs (e.g., anticoagulants)
• diuretics
• enzyme inducers (phenytoin, phenobarbital, carbamazepine)
• cimetidine
• amiodarone
• quinidine
• disopyramide
• verapamil
• nifedipine

Key clinical trials

• Efficacy of Early Rhythm Control Therapy in Patients With Subclinical Atrial Fibrillation (NA)
• Catheter Ablation Versus Anti-arrhythmic Drugs for Premature Ventricular Complexes (NA)
• Pulsed Field Ablation (PFA) vs Anti-Arrhythmic Drug (AAD) Therapy as a First Line Treatment for Persistent Atrial Fibrillation (NA)
• Flecainide Safety in Patients With Coronary Artery Disease and Atrial Fibrillation (PHASE4)
• EfFect of Ablation of Persistent AtriaL Fibrillation on COgNitive Function in Individuals With Mild Cognitive Impairment (NA)
• Dronedarone Rhythm Intervention for Early Atrial Fibrillation (PHASE4)
• Shortening Duration of Antiarrhythmic Medication for SVT in Infants
• The Use of Flecainide for Treatment of Atrial Fibrillation

Primary sources

Every claim on this page is sourced from regulatory or scientific primary sources. See our editorial policy for full methodology.

Competitive intelligence

For the full competitive landscape — auto-detected comparators, recent regulatory actions across the set, upcoming PDUFA, patent timeline, sponsor landscape:

• Tambocor CI brief — competitive landscape report
• Tambocor updates RSS · CI watch RSS