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Phenobarbital for preventing seizures

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Phenobarbital for preventing seizures

This leaflet is about the use of phenobarbital to prevent epileptic seizures. (Seizures may also be called convulsions or fits.)

Information Standard quality markThis leaflet has been written specifically 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.

Name of drug

Phenobarbital
(This drug used to be known as phenobarbitone.)

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

It is important that your child takes phenobarbital regularly so that they have fewer seizures.

What is phenobarbital available as?

  • Tablets: 15 mg, 30 mg, 60 mg; these tablets contain lactose
  • Liquid medicine (orange): 15 mg in 5 mL; this contains a high concentration of alcohol and is not suitable for children with epilepsy

Other liquid medicines that do not contain alcohol can be prepared specially by your pharmacist. Check that you are always given the same strength of medicine.

When should I give phenobarbital?

Phenobarbital may be given once or twice a day.

  • Once a day: This is usually in the evening.
  • 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 sometime between 7 and 8 am and between 7 and 8 pm.

How much should I give?

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

Your doctor will start your child on a low dose and then gradually increase it over a few days or weeks to help your child get used to the medicine. If you are not sure how much to give, check with your doctor or pharmacist.

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

How should I give it?

TabletsTablets should be swallowed whole with a glass of water, milk or juice. Your child should not chew the tablet.
You can crush the tablet and mix it with about 2 tablespoons of fruit juice or soft food such as yogurt, honey or jam. Make sure your child swallows it straight away, without chewing.

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.

When should the medicine start working?

It may take a few weeks for phenobarbital to work properly, so your child may still have seizures during this time. This is because the amount of medicine has to be increased slowly. Continue to give the medicine in the way you have been told to by your doctor or epilepsy nurse. Phenobarbital may not stop your child’s seizures completely. If you are worried about whether it is helping, contact your doctor but continue to give the medicine.

What if my child is sick (vomits)?

  • If your child is sick less than 30 minutes after taking a dose of phenobarbital, give the same dose again.
  • If your child is sick more than 30 minutes after taking a dose of phenobarbital, 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 once a day: If you remember before bedtime, give the missed dose. You do not need to wake up a sleeping child to give a missed dose. You can give the missed dose in the morning, as long as this is at least 12 hours before the evening dose is due.

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. Just give the next dose as usual.

Never give a double dose of phenobarbital.

What if I give too much?

If you think you may have given your child too much phenobarbital, contact your doctor or NHS Direct (0845 4647 in England and Wales; 08454 24 24 24 in Scotland) or take your child to hospital.

Take the medicine packaging with you, even if it is empty. This will be useful to the doctor. Have the 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 cause effects that we don’t want (side-effects).

Phenobarbital usually causes only mild side-effects, which should get better as your child’s body gets used to the medicine. If they are still a problem after 2 weeks or you are worried, contact your doctor, but continue to give phenobarbital.

  • Your child’s behaviour may change – they may be drowsy (sleepy), seem less alert than normal and may say they cannot think clearly or remember things. They may develop a tremor (shakiness), or their coordination may be affected (they may seem clumsy). They may also have changes in mood and may be aggressive or hyperactive (more active than usual and finding it hard to relax). They may have sleep disturbances, such as difficulty getting to sleep.

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 phenobarbital?

  • You can give your child medicines that contain paracetamol or ibuprofen, unless your doctor has told you not to.
  • Some cough medicines and medicines for hay fever could make children drowsy (sleepy) if they are also taking phenobarbital. Check with a doctor or pharmacist before giving any of these medicines to your child.
  • It is important to check with your doctor or pharmacist before giving any other medicines to your child. This includes herbal or complementary medicines.

Epilepsy and pregnancy

  • Pregnancy presents a risk to both the mother with epilepsy and her unborn baby. If your daughter has sex, it is essential that she uses adequate contraception to prevent an unplanned pregnancy.
  • If your daughter thinks that she may be pregnant, it is important that she sees your family doctor as early as possible. Your daughter should keep taking her medication until she sees her doctor.

Phenobarbital and pregnancy

  • Phenobarbital may harm an unborn baby.
  • The oral contraceptive pill can be used safely in women or girls who are taking phenobarbital but its effectiveness may be reduced.

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

  • Some other medicines used to treat epilepsy may affect how well phenobarbital works, or may cause side-effects. If you are worried about side-effects, or if your child seems to be having more fits, contact your doctor or epilepsy nurse.

General advice about medicines for seizures

Do not suddenly stop giving any of these medicines to your child, as they may have a seizure. If you are worried, contact your doctor but carry on giving the medicine to your child as usual.

If your child seems to have more seizures than usual, contact your doctor or epilepsy nurse.

  • If your doctor decides to stop a particular medicine, they will discuss this with you. You will usually reduce the dose bit by bit.

Do not change the dose of any drug without talking to your doctor first.

  • It is best that your child always has the same brand of each medicine, as there may be differences between brands. Keep a record of which medicines your child has.
  • Try to give medicines at about the same times every day, to help you remember.
  • Only give the medicine(s) to your child. Never give them 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 that you always have enough medicine. Order a new prescription at least 2 weeks before you will run out.
  • Make sure that the medicines you have at home have not reached the ‘best before’ or ‘use by’ date on the packaging. Give old medicines to your pharmacist to dispose of.

Where I should keep this medicine?

  • Keep the medicine in a cupboard, away from heat and direct sunlight.
  • You may need to keep liquid medicine in the fridge – check the instructions on the bottle. Make sure that the medicine doesn’t freeze.
  • 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 child’s hospital doctor, epilepsy nurse or pharmacist will be able to give you more information about phenobarbital and other medicines used to treat epilepsy.

You can also get useful information from: 
Publication date: 
09/12/2011

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