Cardiovascular
Flecainide
A class Ic antiarrhythmic — Restores and maintains normal rhythm in selected arrhythmias — only in structurally normal hearts.
Education and reference only. This is a plain-language class overview — it deliberately contains no doses. Always check the current Summary of Product Characteristics (SmPC), the BNF and your local formulary before prescribing or administering any medicine.
What it is
Flecainide is used to restore and maintain normal heart rhythm in selected arrhythmias — particularly atrial fibrillation and some other supraventricular arrhythmias — in people whose hearts are structurally normal.
How it works
It blocks the fast sodium channels that begin each heartbeat's electrical impulse, slowing conduction through the heart and suppressing the abnormal circuits that sustain certain arrhythmias. In a damaged or scarred heart, that same slowing can create dangerous new arrhythmias — which is why a healthy heart structure is essential.
In practice
In practice flecainide is an effective rhythm-control drug for atrial fibrillation and certain other arrhythmias, including as a "pill-in-the-pocket" approach for infrequent attacks in suitable patients, but its use is governed by one defining rule: it must be avoided in people with significant structural or ischaemic heart disease, where it increases the risk of dangerous arrhythmias and death. So before it is used, that is excluded, and in atrial fibrillation it is generally paired with a rate-controlling drug (such as a beta-blocker) to avoid a rapid ventricular response if the rhythm changes. It widens the heart's electrical complexes, so an ECG is used to monitor for excessive effect, and it can unmask or worsen conduction problems. It interacts with other drugs that affect the heart's electrics and is generally started under specialist guidance.
Examples
Practical use
How to take it & use it well
- Flecainide is a tablet taken by mouth to control certain abnormal heart rhythms, such as some forms of atrial fibrillation and other fast rhythms.
- Take it regularly as prescribed, usually at evenly spaced times, and do not stop suddenly without advice.
- It is not suitable if you have had a heart attack or have certain types of structural or coronary heart disease, so your heart is assessed first.
- In atrial fibrillation it is usually combined with a rate-controlling medicine to keep the heart from beating too fast.
- You will have ECG heart tracings before and during treatment to check it is working safely.
- Report fainting, palpitations, breathlessness or a worsening of your symptoms promptly.
Common uses
- Rhythm control in atrial fibrillation (including "pill-in-the-pocket")
- Some other supraventricular arrhythmias
- Selected arrhythmias in structurally normal hearts
Monitoring
- ECG for excessive QRS widening or conduction problems
- Symptoms and rhythm control
- Cardiac structure assessed before use
Weighing it up
Advantages & disadvantages
Advantages
- Can effectively control troublesome fast or irregular heart rhythms and reduce symptoms.
- May restore and help maintain a normal heart rhythm in suitable people.
- Can be used as a planned tablet for occasional episodes in some carefully selected patients.
- Taken by mouth and managed largely at home once stable.
Disadvantages
- Can be dangerous in people with structural or coronary heart disease, where it may worsen rhythms.
- May itself trigger new or more serious abnormal heart rhythms.
- Needs ECG monitoring and is not suitable for everyone.
- Side effects can include dizziness, visual disturbance and breathlessness.
- Should not be stopped or started without specialist guidance.
Key safety principles
What to watch for
- Avoid in significant structural or ischaemic heart disease — risk of dangerous proarrhythmia.
- In atrial fibrillation, usually combined with a rate-controlling drug (e.g. a beta-blocker).
- Widens the heart's electrical complexes — ECG monitoring; interacts with other cardiac drugs.
Key interactions
What to avoid or check alongside
- Other anti-arrhythmic and heart-rhythm medicines can add to its effects on the heart and increase the risk of dangerous rhythms.
- Medicines that slow the heart, such as beta-blockers and some calcium-channel blockers, can add to slowing and need careful balancing.
- Some antidepressants and other medicines that affect how flecainide is broken down can raise its levels and toxicity.
- Used in atrial fibrillation it is paired with a rate-control medicine, because without one the heart can be driven dangerously fast.
Patient & carer advice
- This is only safe if your heart's structure is normal — which we check first
- If you use it "pill-in-the-pocket", follow the exact plan you were given
- Report palpitations, blackouts or breathlessness
Use with
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Answers
Flecainide: frequently asked questions
Why is flecainide not suitable if I have heart disease?
In people who have had a heart attack or have structural or coronary heart disease, flecainide can trigger dangerous heart rhythms. Your heart is assessed first to make sure it is safe for you.
Why do I need another heart medicine alongside flecainide in AF?
In atrial fibrillation, flecainide can sometimes allow the heart to beat very fast. A rate-controlling medicine such as a beta-blocker is usually given with it to prevent this.
Why do I have ECG tracings on flecainide?
Flecainide affects the heart's electrical activity, so ECG tracings are done before and during treatment to confirm it is working safely and not causing harmful rhythm changes.
What is the pill-in-the-pocket approach?
Some carefully selected people take a single dose only when an episode of a fast rhythm starts, rather than every day. This is only done under specialist guidance after it has been shown to be safe for you.
What should I report while taking flecainide?
Tell your team about fainting, palpitations, new or worsening breathlessness, dizziness or visual disturbance, as these may mean the dose or treatment needs reviewing.
Authoritative sources
Always verify against the source
This overview is for orientation. For doses, interactions, contra-indications and the full monograph, use:
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