Usual Adult Dose for Arrhythmias

400-800 mg/day. The recommended dose for most adults is 600 mg/day. Patients < 50 kg may be given 400 mg/day.
Immediate-release form: The dose is divided and administered every 6 hours.
Extended-release form: The dose is divided and administered every 12 hours.

Renal Dose Adjustments

Immediate-release:
CrCl < 15 mL/min: Loading dose: 150 mg orally.
Maintenance dose: 100 mg orally every 24 hours.

CrCl 15-30 mL/min: Loading dose: 150 mg orally.
Maintenance dose: 100 mg orally every 12 hours.

CrCl 30-40 mL/min: Loading dose: 150 mg orally.
Maintenance dose: 100 mg orally every 8 hours.

CrCl > 40 mL/min: Loading dose: 200 mg orally.
Maintenance dose: 100 mg orally every 6 hours.

Extended-release:
CrCl <= 40 mL/min: not recommended
CrCl > 40 mL/min: Maintenance dose: 200 mg (extended-release) orally every 12 hours.

Liver Dose Adjustments

Loading dose: 200 mg orally.
Maintenance dose: 100 mg (immediate-release) orally every 6 hours or 200 mg (extended-release) orally every 12 hours.

Dose Adjustments

If rapid control of ventricular arrhythmia is necessary, an initial loading dose of 300 mg of immediate-release, or 200 mg if patient is < 50 kg is recommended.

Patients with cardiomyopathy should not be given a loading dose and should initially receive 100 mg immediate-release every 6 to 8 hours.

Precautions

US BOXED WARNING:

• MORTALITY: 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 had a myocardial infarction more than 6 days but less than 2 years previously, an excessive mortality or non-fatal cardiac arrest rate (7.7%) was seen in patients treated with encainide or flecainide compared with that seen in patients assigned to carefully matched placebo-treated groups (3%). The average duration of treatment with encainide or flecainide in this study was 10 months. The applicability of the CAST results to other populations (e.g., those without recent myocardial infarction) is uncertain. Considering the known proarrhythmic properties of this drug and the lack of evidence of improved survival for any antiarrhythmic drug in patients without life-threatening arrhythmias, the use of this drug as well as other antiarrhythmic agents should be reserved for patients with life-threatening ventricular arrhythmias.

Dialysis

Data not available

Other Comments

A limited number of patients have tolerated up to 400 mg orally every 6 hours.