Usual Adult Dose for Ventricular Tachycardia

Initial dose: 100 mg orally every 12 hours.
Maintenance dose: May be increased in increments of 50 mg bid every 4 days until efficacy is achieved. Most patients with SUSTAINED VT do not require more than 150 mg every 12 hours (300 mg/day), and the maximum dose recommended is 400 mg/day.

Usual Adult Dose for Atrial Fibrillation

Initial dose: 50 mg orally every 12 hours.
Maintenance dose: May be increased in increments of 50 mg bid every 4 days until efficacy is achieved.

Usual Adult Dose for Atrial Flutter

Initial dose: 50 mg orally every 12 hours.
Maintenance dose: May be increased in increments of 50 mg bid every 4 days until efficacy is achieved.

Usual Adult Dose for Wolff-Parkinson-White Syndrome

Initial dose: 50 mg orally every 12 hours.
Maintenance dose: May be increased in increments of 50 mg bid every 4 days until efficacy is achieved.

Usual Adult Dose for Paroxysmal Supraventricular Tachycardia

Initial dose: 50 mg orally every 12 hours.
Maintenance dose: May be increased in increments of 50 mg bid every 4 days until efficacy is achieved.

Usual Pediatric Dose for Supraventricular Tachycardia

less than 1 month:
Supraventricular tachycardia: Limited data available: Initial: 2 mg/kg/day orally divided every 12 hours; titrate to clinical response, monitor serum concentration; mean dose required to suppress SVT: 3.35 ± 1.35 mg/kg/day in 17 neonates (n=20 treated neonates; mean PNA: 11.5 days; mean GA: 36.8 weeks; mean birthweight: 2.8 kg); study did not report resultant serum concentrations.

1 month or older:
Initial: 1 to 3 mg/kg/day orally or 50 to 100 mg/m2/day orally in 3 divided doses; usual: 3 to 6 mg/kg/day or 100 to 150 mg/m2/day in 3 divided doses; up to 8 mg/kg/day or 200 mg/m2/day for uncontrolled patients with subtherapeutic levels; higher doses have been reported, however they may be associated with an increased risk of proarrhythmias; a review of world literature reports the average effective dose to be 4 mg/kg/day or 140 mg/m2/day.

Renal Dose Adjustments

CrCl=35 mL/min or less: Initial dose: 100 mg orally once a day or 50 mg twice a day. It may take longer than 4 days before a new steady-state plasma level is reached following a dosage change.

In patients with less severe renal dysfunction: Initial dose: 100 mg every 12 hours.

Liver Dose Adjustments

Flecainide should not be used in patients with significant liver dysfunction unless the potential benefits clearly outweigh the risks, as elimination from plasma can be markedly slower in patients with significant hepatic impairment. If it is deemed necessary, frequent and early plasma level monitoring is required to guide dosage and dosage increases should be made very cautiously when plasma levels have plateaued (after more than four days).

Dose Adjustments

Patients not adequately controlled by (or intolerant to) a dose given at 12 hour intervals may be dosed at 8 hour intervals.
Once adequate control of the arrhythmia has been achieved, it may be possible in some patients to reduce the dose as necessary to minimize side effects or effects on conduction. In such patients, efficacy at the lower dose should be evaluated.

Dosing adjustments based on gender may be required. In a pharmacokinetic study involving Japanese patients with supraventricular tachyarrhythmias, nonrenal clearance of flecainide was significantly higher and plasma levels significantly lower in males than in females. Consequently, antiarrhythmic efficacy was significantly lower in males than in females. Japanese male patients may require higher doses in order to achieve therapeutic plasma levels (i.e., approximately 400 ng/mL) of flecainide compared with females.

Precautions

US BOXED WARNINGS:

• MORTALITY: This drug 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 6 days but less than 2 years previously. An excessive mortality or non-fatal cardiac arrest rate was seen in patients treated with this drug compared with that seen in patients assigned to a carefully matched placebo-treated group. The rate was 16/315 (5.1%) for this drug and 7/309 (2.3%) for the matched placebo. The average duration of treatment with this drug in this study was 10 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 this drug), 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, signs or symptoms.
• VENTRICULAR PROARRHYTHMIC EFFECTS IN PATIENTS WITH ATRIAL FIBRILLATION/FLUTTER: A review of the world literature revealed reports of 568 patients treated with the oral formulation of this drug for paroxysmal atrial fibrillation/flutter. 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 ventricular tachycardia (VT) or ventricular fibrillation (VF). This drug is not recommended for use in patients with chronic atrial fibrillation. Case reports of ventricular proarrhythmic effects in patients treated with this drug for atrial fibrillation/flutter have included increased premature ventricular contractions, VT, VF, and death. As with other Class I agents, patients treated with this drug 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 this drug. Concomitant negative chronotropic therapy such as digoxin or beta-blockers may lower the risk of this complication.

• This drug should be considered a narrow therapeutic index (NTI) drug as small differences in dose or blood concentrations may lead to serious therapeutic failures or adverse drug reactions.

• Generic substitution should be done cautiously, if at all, as current bioequivalence standards are generally insufficient for NTI drugs.
• Additional and/or more frequent monitoring should be done to ensure receipt of an effective dose while avoiding unnecessary toxicities.

Dialysis

Flecainide is not dialyzable (0%-5%) via hemo- or peritoneal dialysis. A supplemental dose is not necessary.

Other Comments

The maximum recommended dose for patients with PSVT is 300 mg/day.
The maximum recommended dose for patients with Sustained VT is 400 mg/day.

Monitoring of electrolytes (i.e., potassium, sodium) periodically has been recommended in high-risk patients in order to prevent flecainide cardiotoxicity.