TAMBOCOR

What it is

TAMBOCOR 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 AV nodal pathways in patients with debilitating symptoms. — Paroxysmal atrial fibrillation/flutter associated with disabling symptoms. — Life threatening ventricular arrhythmias not controlled by other drugs, used for continuous maintenance of normal rhythm following initial oral or intravenous therapy or conversion by other means.

Dosing overview

The dosage of flecainide acetate must be adjusted to the individual needs of each patient based on therapeutic response and tolerance, and dosage may need to be modified if the age, weight, or clinical status of the patient dictates. Steady-state plasma levels may not be achieved until 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

Although flecainide acetate may be effective in supraventricular arrhythmias in patients with structural heart disease, its use has been associated with life-threatening and occasionally fatal ventricular arrhythmias; in these patients, particularly in the presence of impaired left ventricular function, flecainide acetate should be used with extreme caution, preferably after other antiarrhythmic drugs have been tried or considered inappropriate. In the Cardiac Arrhythmia Suppression Trial, oral flecainide was associated with a higher incidence of mortality or non-fatal cardiac arrest in patients with asymptomatic non-life threatening ventricular arrhythmias who had myocardial infarction, and an even higher incidence of mortality was 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; 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 has a mild negative inotropic effect and may cause or worsen congestive heart failure, particularly in patients with cardiomyopathy, pre-existing severe heart failure (NYHA functional class III or IV) or ejection fractions ≤ 40%; it should be used cautiously in patients with a history of congestive heart failure or myocardial dysfunction. Use of flecainide acetate in chronic atrial fibrillation has not been adequately studied and is not recommended.

Contraindications

TAMBOCOR is contraindicated in: second or third degree A-V block unless a pacemaker is present; right bundle branch block associated with a left hemi-block (bifascicular block) unless a pacemaker is present; 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; and in patients with severe renal or hepatic impairment unless plasma level monitoring can be done.

Key safety warnings (Adverse effects)

The most serious adverse reactions reported for flecainide acetate in patients with ventricular arrhythmias were new or exacerbated ventricular arrhythmias which occurred in 6.8% of patients and new or worsened congestive heart failure which occurred in 3.9% of patients. The most commonly reported non-cardiac adverse reactions experienced by patients with ventricular arrhythmias were dizziness 27%, visual disturbance 26% (includes blurred vision, diplopia, visual field effects, photophobia), headache 10%, nausea 10% and dyspnoea 9%.

Regulatory history

TAMBOCOR flecainide acetate 50 mg tablets were first listed on the ARTG on 27 August 1992, and 100 mg tablets were also first listed on 27 August 1992.