Flecainide for irregular heartbeats

Last updated by Peer reviewed by Sid Dajani
Last updated Meets Patient’s editorial guidelines

Added to Saved items

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.

Type of medicineAn anti-arrhythmic medicine
Used forIrregular heartbeats
Available asTablets 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.
  • 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.

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 dizzyDo 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.

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.

Are you protected against flu?

See if you are eligible for a free NHS flu jab today.

Check now

Further reading and references