Flecainide

Flecainide is a medication (‘antiarrhythmic’) used to treat atrial fibrillation, ventricular ectopic beats, and supraventricular tachycardia.

Mechanism

Flecainide slows the activation of sodium channel proteins in the heart. This suppresses ectopic “extra” beats in the atrium which trigger atrial fibrillation and supraventricular tachycardia, and will also suppress symptomatic ventricular ectopic “extra” beats.

Dosage

The usual dose of flecainide is 50mg every 12 hours, with the dose increased to 100-150mg twice a day depending on response and tolerability.

It typically starts working within 1-3 hours, but it may be some days before it has maximum effect. If it is not working after 5-7 days then the dose can be increased.

While flecainide can suppress abnormal rhythms, rarely it can cause abnormal heart rhythm. In some patients treated for atrial fibrillation, flecainide triggers another rhythm problem called atrial flutter. This can cause the heart to beat very quickly. To prevent this fast heart, flecainide is always given with a second ‘slowing’ medication. Typically this will be a ‘calcium channel blocker’ e.g. verapamil or diltiazem, or a ‘beta blocker’ e.g. metoprolol, atenolol, or bisoprolol; and sometimes a ‘glycoside’ called digoxin.

Monitoring

Like all antiarrhythmic medication, flecainide requires careful monitoring.

It can only be used when the heart is healthy and structurally normal, and there is no severe coronary artery disease.

Before starting flecainide you will be asked about typical symptoms of coronary artery disease (e.g. chest pain or shortness of breath), and you may have a scan to rule out coronary artery disease.

An ECG is performed to check that the baseline electrical activity of the heart is normal.

Lastly, an echocardiogram is performed to examine the function and structure of the heart.

An ECG is repeated once you have started flecainide to examine its effect on the electrical activity of the heart.

These same tests will be repeated every 1-2 years while you remain on flecainide.

Side Effects/Interactions

Non-cardiac: dizziness, blurred vision, headaches and nausea. Cardiac: slow heart beat, fainting due to slow or fast heart beat (uncommon) - it is very important that you attend emergency if you faint while taking flecainide.

Drug Interactions (Advanced)

Flecainide is metabolized by the liver enzyme CYP2D6. Therefore, drugs which inhibit CYP2D6 may increase the level of flecainide in the blood stream and increase the risk of toxicity.

Examples of CYP2D6 inhibitors include: paroxetine (SSRI), fluoxetine (SSRI), quinidine (antiarrhythmic), amiodarone (antiarrhythmic), duloxetine (SNRI), and sertraline (SSRI).

Conversely, flecainide may increase the level of digoxin in the blood.

Flecainide may accumulate in kidney failure. The effect is unpredictable, but requires more careful monitoring. It is not removed by haemodialysis.

Summary

If used and monitored carefully, in a structurally normal and healthy heart, flecainide is a safe and effective medication for the treatment of atrial fibrillation, SVT, and ventricular ectopic beats.