Flecainide for arrhythmias

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Flecainide for arrhythmias

This leaflet is about the use of flecainide for the treatment of heart rate that is too fast (called tachycardia) or is irregular (called arrhythmia).

This leaflet has been written specifically for parents and carers about the use of this medicine in children. The information may differ from that provided by the manufacturer. Please read this leaflet carefully. Keep it somewhere safe so that you can read it again.

If your child has not eaten for more than 24 hours, for example if they have gastroenteritis (a tummy bug), contact your specialist doctor, as there is a chance of more serious side-effects from taking flecainide. Your doctor may want to reduce the dose for a few days.

Name of drug

Brand name:

Why is it important for my child to take this medicine?

Flecainide will help your child’s heart to beat at a normal rate and with a normal pattern (rhythm) so that it works properly to pump blood. It can be used for a range of arrhythmias including supraventricular tachycardia (sometimes called SVT), ventricular tachycardia, ventricular ectopic beats, Wolff–Parkinson–White syndrome and atrial fibrillation.

What is flecainide available as?

  • Tablets: 50 mg, 100 mg
  • Capsules: 200 mg
  • Liquid medicine: 25 mg in 5 mL

When should I give flecainide?

Flecainide is usually given two or three times a day.  Your doctor will tell you how often to give it.

  • Twice a day: this should be once in the morning and once in the evening. Ideally, these times are 10–12 hours apart, for example some time between 7 and 8 am and between 7 and 8 pm.
  • Three times a day: this should be once in the morning, once in the early afternoon and once in the evening. Ideally, these times are at least 6 hours apart, for example 8 am, 2 pm and 8 pm.

Give the medicine at about the same times each day so that this becomes part of your child’s daily routine, which will help you to remember.

How much should I give?

Your doctor will work out the amount of flecainide (the dose) that is right for your child. The dose will be shown on the medicine label.

It is important that you follow your doctor’s instructions about how much to give.

How should I give it?

Your child should not have milk, including breast milk, infant formula feed or dairy products (cheese, cream, yogurt) at the same time as flecainide, as the medicine will not be absorbed from the stomach properly. You should allow at least one hour, preferably two hours, between feeding and giving flecainide. 

TabletsTablets should be swallowed with a glass of water or juice, but not milk. Your child should not chew the tablet.

CapsuleCapsules should be swallowed with a glass of water or juice, but not milk. Your child should not chew the capsule.

Liquid medicine with oral syringeLiquid medicine: Measure out the right amount using an oral syringe or medicine spoon. You can get these from your pharmacist. Do not use a kitchen teaspoon as it will not give the right amount. The liquid medicine may make your child’s mouth feel numb for a short while. Give it at least an hour before or after food.

When should the medicine start working?

It may take a few days for flecainide to have an effect. Continue to give flecainide regularly during this time.

What if my child is sick (vomits)?

  • If your child is sick less than 30 minutes after having a dose of flecainide, give them the same dose again.
  • If your child is sick more than 30 minutes after having a dose of flecainide, you do not need to give them another dose. Wait until the next normal dose.

What if I forget to give it?

  • If you usually give it twice a day: If you remember up to 4 hours after you should have given a dose, give your child the missed dose. For example, if you usually give a dose at about 7 am, you can give the missed dose at any time up to 11 am. If you remember after that time, do not give the missed dose. Wait until the next normal dose.
  • If you usually give it three times a day: Do not give the missed dose. Just give the next dose as usual.

Never give a double dose of flecainide.

What if I give too much?

It may be dangerous to give too much flecainide.

If you are concerned that you may have given too much, contact your doctor or local NHS services (call 111 in England and Scotland; 111 or 0845 4647 in parts of Wales).  

Take the medicine container or packet with you, even if it is empty. This will be useful to the doctor. Have the medicine or packaging with you if you telephone for advice.

Are there any possible side-effects?

We use medicines to make our children better, but sometimes they have other effects that we don’t want (side-effects).

Side-effects you must do something about

If your child is short of breath or is wheezing, or their face, lips or tongue start to swell, or they develop a rash, they may be allergic to flecainide. Take your child to hospital or call an ambulance straight away.

If your child’s heartbeat changes, starts to pound or beats faster (they may say their heart feels fluttery or is racing) or slower than usual, or if they have chest pain or become short of breath, call for an ambulance or take your child to hospital straight away. This may be a sign of a problem with the heart rate, which may need treatment.

Very rarely, flecainide causes seizures (convulsions or fits). If your child has a seizure, telephone for an ambulance straight away. Do not restrain your child, but try to make sure that they cannot hurt themselves. Put them in the recovery position (on their side).

If your child gets a yellowish tinge to the skin or whites of the eyes, or they have severe stomach pain or a high temperature (above 38°C), contact your doctor straight away, as there may be a problem with their liver.

  • Your child may say that they see black spots or that their eyesight is blurred (fuzzy), or they see double. Contact your doctor if this happens.
Other side-effects you need to know about
  • Your child may have stomach pain, feel sick or be sick (vomit), feel bloated, have wind, diarrhoea or constipation (difficulty doing a poo) when they first start taking flecainide. If these symptoms carry on for more than a week, contact your doctor.
  • Your child may feel less hungry (lose their appetite). Encourage them to eat small meals often.
  • Your child may feel dizzy or light-headed when they stand up. Encourage them to stand up slowly and to sit or lie down if they fell dizzy or light-headed.
  • Your child may be more tired than usual and may feel weak. They may also seem more forgetful. These effects should wear off. If they are still a problem after 2 weeks or if you are worried, contact your doctor.
  • Your child’s skin may seem more sensitive and they may get a rash or itchiness. Try applying a moisturising cream or anti-itch cream. If this does not help, contact your doctor, in case your child is allergic to flecainide.
  • Your child’s skin will be more sensitive to the sun while they are taking flecainide. Keep them out of strong sun. They should wear a long-sleeved top, trousers and a hat and should use a high-factor sun screen (at least SPF 30).

There may, sometimes, be other side-effects that are not listed above. If you notice anything unusual and are concerned, contact your doctor.

Can other medicines be given at the same time as flecainide?

  • You can give your child medicines that contain paracetamol or ibuprofen, unless your doctor has told you not to.
  • Flecainide should not be taken with some medicines that you get on prescription. Check with your doctor or pharmacist before giving any other medicines to your child. This includes herbal or complementary medicines.

Is there anything else I need to know about this medicine?

  • Flecainide liquid medicine has a local anaesthetic effect so your child’s mouth may feel numb for a while after taking it. They should not eat for about an hour after taking it, in case they bite their tongue.
  • Your doctor may take blood samples to measure how much flecainide is in your child’s blood.
  • If your daughter thinks that she may be pregnant, it is important that she sees your family doctor as soon as possible. She should keep taking her medicine until she sees her doctor.

General advice about medicines

  • If you are not sure a medicine is working, contact your doctor, but continue to give the medicine as usual in the meantime. Do not give extra doses, as you may do harm.
  • Only give this medicine to your child. Never give it to anyone else, even if their condition appears to be the same, as this could do harm.

If you think someone else may have taken the medicine by accident, contact your doctor straight away.

  • Make sure you always have enough medicine. Order a new prescription at least 2 weeks before you will run out.
  • Make sure that the medicine you have at home has not reached the ‘best before’ or ‘use by’ date on the packaging.

Where I should keep this medicine?

  • Keep the medicines in a cupboard, away from heat and direct sunlight.

Liquid medicine should be stored at room temperature as it will precipitate (powder will form in the medicine) if it is put in the fridge.

  • Make sure that children cannot see or reach the medicine.
  • Keep the medicine in the container it came in.

Who to contact for more information

Your doctor or pharmacist will be able to give you more information about flecainide and about other medicines used to treat arrhythmias.

You can also get useful information from: 
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