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Flecainide for irregular heartbeats

Flecainide is used to treat irregular heartbeats.

The treatment will usually be started for you in hospital by a heart specialist.

It may make you feel dizzy at first. Other side-effects include blurred vision and a lack of energy.

At a glance

  • Flecainide is a medicine used to treat irregular heart rhythms.

  • It works by helping to correct irregular heartbeats to a normal rhythm and slowing an overactive heart.

  • Take flecainide tablets twice a day, around the same times, before or after food.

  • Tell your doctor if you have other heart problems, or kidney or liver issues.

  • Do not drive or use machines if you experience blurred vision or dizziness.

  • Contact your doctor if you have breathing difficulties, chest pain, feel hot, or feel faint.

Continue reading below

About flecainide

Type of medicine

An anti-arrhythmic medicine

Used for

Irregular heartbeats

Available as

Tablets and injection

Flecainide is used to treat arrhythmias. An arrhythmia is an irregularity in your heartbeat, which causes your heart to skip a beat, beat unevenly or beat very fast or very slowly.

Flecainide works by correcting irregular heartbeats to a normal rhythm and by slowing an overactive heart. It will be prescribed for you by a heart specialist doctor. There are two strengths of tablet available (50 mg and 100 mg).

Some medicines are not suitable for people with certain conditions, and sometimes a medicine may only be used if extra care is taken. For these reasons, before you start taking flecainide it is important that your doctor knows:

  • If you have a pacemaker fitted or if you have any heart problems other than your abnormal heart rhythm. In particular, let your doctor know if you have heart failure, or if you have had a heart attack.

  • If you have any problems with the way your liver works, or any problems with the way your kidneys work.

  • If you are pregnant or breastfeeding.

  • If you are taking or using any other medicines. This includes any medicines you are taking which are available to buy without a prescription, as well as herbal and complementary medicines.

  • If you have ever had an allergic reaction to a medicine.

Continue reading below

  • Before you start the treatment, read the manufacturer's printed information leaflet from inside the pack. It will give you more information about flecainide and will provide you with a full list of the side-effects which you may experience from taking it.

  • Your doctor will tell you what the right dose of flecainide is for you. The dose may need to be adjusted as your symptoms become controlled, so make sure you take flecainide exactly as your doctor tells you to. Flecainide tablets are usually taken twice each day. Your dose will be printed on the label of the pack to remind you about what the doctor said to you.

  • Try to take your doses around the same times of day, as this will help you to remember to take them regularly.

  • You can take flecainide tablets either before or after food.

  • If you forget to take a dose, leave out the missed dose but make sure that you remember to take your next dose when it is due. Do not take two doses together to make up for a forgotten dose.

  • Try to keep your regular appointments with your doctor. This is so your doctor can check your heart rhythm and monitor your progress.

  • Treatment with flecainide is usually long-term unless you experience an adverse effect. You should continue to take it unless you are advised otherwise by your doctor.

  • If you are having an operation or any medical/dental treatment, remember to tell the person carrying out the treatment that you are taking flecainide. This is because it can interfere with some local anaesthetics and increase the risk of side-effects.

  • If you buy any medicines 'over the counter', always check with a pharmacist that they are suitable for you to take alongside your other medicines. A medicine called cimetidine (which is taken to reduce stomach acid) can interfere with flecainide.

Continue reading below

Along with their useful effects, most medicines can cause unwanted side-effects although not everyone experiences them. The table below contains some of the most common ones associated with flecainide. You will find a full list in the manufacturer's information leaflet supplied with your medicine. The unwanted effects often improve as your body adjusts to the new medicine, but speak with your doctor or pharmacist if any of the following continue or become troublesome.

Very common flecainide side-effects (these affect more than 1 in 10 people)


What can I do if I experience this?

Blurred or double vision, feeling dizzy

Do not drive and do not use tools or machines

Common flecainide side-effects

(these affect fewer than 1 in 10 people)

What can I do if I experience this?

Feeling weak or tired, lack of energy, fluid retention (causing swollen hands or feet)

If troublesome, speak with your doctor

Important: there have been reports of flecainide causing unwanted heartbeat changes in some people. This has caused symptoms such as difficulties with breathing, chest pain, feeling hot and feeling faint. If you experience any of these symptoms, you should contact your doctor for advice straightaway.

If you experience any other symptoms which you think may be due to flecainide, speak with your doctor or pharmacist for further advice.

  • Keep all medicines out of the reach and sight of children.

  • Store in a cool, dry place, away from direct heat and light.

Important information about all medicines

Never take more than the prescribed dose. If you suspect that you or someone else might have taken an overdose of this medicine, go to the accident and emergency department of your local hospital. Take the container with you, even if it is empty.

This medicine is for you. Never give it to other people even if their condition appears to be the same as yours.

Do not keep out-of-date or unwanted medicines. Take them to your local pharmacy which will dispose of them for you.

If you have any questions about this medicine ask your pharmacist.

Report side effects to a medicine or vaccine

If you experience side effects, you can report them online through the Yellow Card website.

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Unsure about mixing medicines?

Check for possible interactions between medicines, supplements and foods before taking them together.

Frequently asked questions

What kind of heart conditions does flecainide treat?

Flecainide is specifically prescribed for arrhythmias, which are irregularities in your heartbeat. This includes situations where your heart might skip a beat, beat unevenly, too fast, or too slowly, and it works by helping to restore a normal heart rhythm or slow down an overactive heart.

Why is it important for my doctor to know about my other health conditions before I start flecainide?

It's important for your doctor to know about other health conditions because some medicines aren't suitable for certain conditions, or might need extra care. For flecainide, in particular, your doctor needs to know if you have a pacemaker, other heart problems (like heart failure or a past heart attack), or issues with your liver or kidneys. This helps ensure the medicine is safe and appropriate for you.

Can I take flecainide with other medicines?

You should tell your doctor about all other medicines you are taking, including those bought without a prescription, and herbal or complementary medicines. For example, a medicine called cimetidine, used for stomach acid, can interfere with flecainide. Always check with a pharmacist if buying over-the-counter medicines to ensure they are suitable to take with flecainide.

How often will I need to see my doctor while taking flecainide?

You should try to keep your regular appointments with your doctor while taking flecainide. These appointments are important so your doctor can regularly check your heart rhythm and monitor how you are progressing with the treatment.

What should I do if I forget to take a dose of flecainide?

If you forget a dose of flecainide, you should leave out the missed dose completely. Then, just make sure to take your next dose when it is due. Do not take two doses together to try and make up for the one you missed.

Are there any activities I should avoid if I experience side-effects like blurred vision or dizziness?

If you experience side-effects such as blurred or double vision, or if you feel dizzy, it's important not to drive a car or operate any tools or machinery. These common side-effects can affect your ability to perform these activities safely.

How should I store flecainide tablets at home?

You should keep all flecainide tablets out of the reach and sight of children. Store them in a cool, dry place, away from any direct heat and light, to ensure they remain effective.

Further reading and references

Continue reading below

About the authorView full bio

Author image

Michael Stewart, MRPharmS

Medicine Leaflet Review Manager – Contractor, Pharmacist

BPharm (Hons), MRPharmS

Michael is a community pharmacist practicing in the Midlands and South Yorkshire with more than 20 years’ experience advising on medicines and medical conditions. He has a strong background in healthcare training, having produced and delivered training courses for pharmacy teams and staff of residential care settings, including nurses. He has also contributed to pharmacy advisory boards for the management of low acuity conditions in the community.

About the reviewer

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Sid Dajani

Sultan Dajani qualified at the London School of Pharmacy in 1994 and became the youngest elected member of the Royal Pharmaceutical Society council since its founding in 1842.

Article history

The information on this page is written and peer reviewed by qualified clinicians.

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