APO-FLECAINIDE

What it is

APO-FLECAINIDE contains flecainide acetate in 50 mg and 100 mg tablet strengths. Flecainide acetate belongs to the membrane stabilising (Class 1) group of antiarrhythmic agents. The predominant action of flecainide acetate is to inhibit the fast, or sodium, channel which is largely responsible for the rapid upstroke of the myocardial action potential in cardiac conducting tissue.

Approved indications —

Supraventricular arrhythmias due to pre-excitation syndromes such as Wolff-Parkinson-White and Lown-Ganong-Levine syndromes — Supraventricular arrhythmias due to dual atrioventricular nodal pathways in patients with debilitating symptoms — Paroxysmal atrial fibrillation/flutter associated with disabling symptoms — Life threatening ventricular arrhythmias not controlled by other drugs, for continuous maintenance of normal rhythm following initial oral or intravenous therapy or conversion by other means

Dosing overview

Steady-state plasma levels in patients with normal renal and hepatic function may not be achieved until the patient has received 3 to 5 days of therapy at a given dose, so increases in dosage should be made no more frequently than once every four days.

Key safety warnings

In the Cardiac Arrhythmia Suppression Trial, oral flecainide was associated with a higher incidence of mortality or non-fatal cardiac arrest (19 of 323 patients) compared with placebo (7 of 318 patients) in patients with asymptomatic non-life threatening ventricular arrhythmias who had myocardial infarction more than six days but less than two years previously, with an even higher incidence of mortality observed in flecainide-treated patients with more than one myocardial infarction. Patients with structural heart disease treated with flecainide for supraventricular arrhythmias may be at increased risk for proarrhythmia and cardiac adverse events, and the use of flecainide in these patients has been associated with life-threatening and occasionally fatal ventricular arrhythmias, particularly in the presence of impaired left ventricular function with ejection fraction ≤ 40%. Flecainide acetate is not recommended for use in patients with chronic atrial fibrillation. A review of the world literature revealed that ventricular tachycardia was experienced in 0.4% (2 of 568) of patients treated with oral flecainide acetate for paroxysmal atrial fibrillation/flutter, but of 19 patients with chronic atrial fibrillation, 10.5% (2 of 19) experienced ventricular tachycardia or ventricular fibrillation. Because flecainide acetate has a mild negative inotropic effect, it may cause or worsen congestive heart failure, particularly in patients with cardiomyopathy, pre-existing severe heart failure (New York Heart Association functional class III or IV) or ejection fractions ≤ 40%, and should therefore be used cautiously in patients who are known to have a history of congestive heart failure or myocardial dysfunction. Flecainide acetate slows cardiac conduction sufficiently in most patients to produce measurable increases in the duration of the PR, QRS and QT intervals on the electrocardiogram, with increases of more than 25% in the duration of the PR interval occurring commonly and approximately one third of patients developing first-degree heart block, and widening of the QRS of 25% or more also being common.

Contraindications

— Second or third degree atrioventricular block, unless a pacemaker is present to sustain rhythm — Right bundle branch block when associated with a left hemi-block (bifascicular block) unless a pacemaker is present to sustain rhythm — Cardiogenic shock — Asymptomatic premature ventricular contractions and/or asymptomatic non-sustained ventricular tachycardia in patients with a history of myocardial infarction — Known hypersensitivity to the drug — Severe renal or hepatic impairment unless plasma level monitoring can be done

Regulatory history

APO-FLECAINIDE was first listed on the Australian Register of Therapeutic Goods on 19 June 2018, with two registered variants: the 50 mg tablet blister pack (ARTG 289980) and the 100 mg tablet blister pack (ARTG 289979).