Flecainide: rhythm control tablet, ECG checks and who must avoid it

Flecainide is an anti-arrhythmic medicine. The SmPC describes its use for severe arrhythmias such as ventricular tachycardia, atrial fibrillation and supraventricular tachycardias when other treatments have failed or cannot be used.

Because of the exclusions listed below, the decision to use it rests on a cardiac assessment.

For adults and adolescents aged 13 and over the SmPC describes starting at 50 to 100mg twice daily, with a maximum of 300 to 400mg a day. In older people the initial maximum is 100mg a day with a limit of 300mg daily. Children under 12 are not recommended to take it.

Follow the label from your specialist and never adjust the dose yourself. Keep all review appointments because dose changes are guided by ECG findings.

The SmPC lists cardiac failure, post-myocardial-infarction patients with asymptomatic ventricular arrhythmias, and known Brugada syndrome as contraindications. It states that flecainide has been shown to increase mortality risk in people after a heart attack who have asymptomatic ventricular arrhythmia, and it can unmask Brugada syndrome.

Tell your cardiologist about any heart attack, heart failure, inherited rhythm condition or pacemaker. Flecainide can also raise the pacing threshold in people with pacemakers.

ECG monitoring is a central safeguard. The SmPC describes frequent ECGs while the dose is being found, and routine monitoring afterwards. Potassium and other electrolyte disturbances should be corrected before treatment because they affect the risk of rhythm problems.

Expect specialist follow-up. If you have symptoms such as fainting, palpitations that feel different, or breathlessness, seek urgent medical help, as these can indicate a pro-arrhythmic effect.

Avoid combining flecainide with other class I anti-arrhythmics. With amiodarone the dose of flecainide is reduced by half. Medicines that block the liver enzyme CYP2D6, such as fluoxetine, paroxetine and ritonavir, increase flecainide levels.

Because many everyday medicines can matter, show your pharmacist a full list and tell any new prescriber you take flecainide.

The most common effects are dizziness and visual disturbances, such as blurred vision. The more serious risk is a pro-arrhythmic effect, meaning that the medicine itself can provoke a rhythm problem, particularly in people with structural heart disease, which is why selection and ECG follow-up are so strict.

Report suspected side effects through the MHRA Yellow Card scheme. If you feel faint, have chest pain or a racing heart that does not settle, call 999.

People who are prescribed flecainide often benefit from asking why it was chosen over other rhythm medicines, since the SmPC places it where other treatments have failed or cannot be used. It is reasonable to ask which tests showed that your heart structure is suitable, how often an ECG will be repeated, and which symptoms should make you seek help quickly.

Bring an up-to-date list of tablets, including antidepressants and anything bought from a pharmacy, because fluoxetine, paroxetine and ritonavir are specifically named as raising flecainide levels. Keep a note of any family history of sudden unexplained death or inherited rhythm conditions, as Brugada syndrome is a contraindication, and make sure each new clinician knows you take it.