Skip to main content

Zonisamide for epilepsy

Zonegran, Desizon

You need to take zonisamide regularly. Do not stop taking it unless your doctor tells you to.

Make sure you drink plenty of water and take care not to become overheated in warm weather.

The most common side-effects are feeling dizzy or sleepy, and lack of appetite.

Continue reading below

About zonisamide

Type of medicine

An antiepileptic medicine

Used for

Epilepsy in adults and in children over 6 years of age

Also called

Zonegran®; Desizon®

Available as

Capsules and oral liquid medicine

Having epilepsy means that you have had more than one unexplained fit, or seizure. A seizure is a short episode of symptoms caused by a burst of abnormal electrical activity in your brain. With partial seizures (also called focal seizures), the burst of electrical activity is in one part of your brain and therefore you tend to have localised or 'focal' symptoms. Because different parts of the brain control different functions, your symptoms will depend on which part of your brain is affected. Partial seizures can sometimes develop into seizures which affect all of your brain. These are called secondary generalised seizures. Symptoms that may occur during a seizure can affect your muscles, sensations, behaviour, emotions, consciousness, or a combination of these.

The seizures can be prevented in most people by suitable antiepileptic medication. Zonisamide works by stabilising the electrical activity of your brain. This helps to prevent the seizures from occurring.

Before taking zonisamide

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 (or your child if you are their carer) start taking zonisamide it is important that your doctor knows:

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

  • If you have ever had a kidney stone.

  • If you have ever had any problems with your vision or with your eyes - for example, raised pressure in your eye(s), a condition known as glaucoma.

  • If you are pregnant, trying for a baby or breastfeeding.

  • If you are taking 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. This is especially important if you have had an allergic reaction to a sulfonamide antibiotic medicine.

  • If you have an allergy to peanuts or to soya.

Continue reading below

How to take zonisamide

  • Before you start the treatment, read the manufacturer's printed information leaflet from inside the pack and any additional information you are given by your doctor. The manufacturer's leaflet will give you more information about zonisamide and will provide you with a full list of the side-effects which you may experience from taking it.

  • Take zonisamide exactly as your doctor tells you to. You will be prescribed either one or two doses to take each day. Your dose will be printed on the label of the pack to remind you about what the doctor said. There are several different strengths of zonisamide capsules. It is usual to start treatment on a low dose, and then for the dose to be increased gradually to a regular maintenance dose.

  • It is important you try to take your doses at the same times each day. Having a routine will help you to remember to take your doses regularly.

  • Swallow the capsule with a drink of water. You can take zonisamide either before or after a meal.

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

Getting the most from your treatment

  • When you first start a new treatment for epilepsy there may be a change in the number or type of seizures you experience. Your doctor will advise you about this.

  • Make sure you drink plenty of water while you are on zonisamide. This is because some people who have taken zonisamide have developed kidney stones - drinking plenty of water will help to prevent this. Occasionally, people taking zonisamide have had heatstroke - drinking plenty of water will also help to prevent this. This is especially important for active children during warm weather, and for people working in a hot environment:

    • Symptoms of heat stroke are: a hot dry skin, feeling confused, muscle cramps, rapid breathing, and a rapid heartbeat.

    • What to do if you suspect heat stroke: move into a cool place and drink cold water. Get medical help straightaway and, in the meantime, sponge your (or your child's) skin with cool water.

  • Try to keep your regular appointments with your doctor. This is so your doctor can check on your progress.

  • While you are being treated for epilepsy there is a small risk that you may develop mood changes, distressing thoughts and feelings about suicide. If this happens, you must tell your doctor about it straightaway.

  • Many antiepileptic medicines can harm an unborn child. If you are a woman, make sure you have discussed with your doctor which types of contraception are suitable for you and your partner. If you want to have a family, discuss this with your doctor so that you can be given advice from a specialist before you become pregnant. You should use effective contraception during treatment with zonisamide and for at least one month after stopping.

  • Different formulations of some antiepileptic medicines can act in a slightly different way in your body. Because of this, your doctor may recommend that you continue to take zonisamide from the same manufacturer each time you obtain a new supply. If so, each time you collect a prescription, check to make sure your supply looks the same and that the name is the same. If you are unsure, or if you have any questions about your prescription, please ask your pharmacist to advise you.

  • People with epilepsy must stop driving at first. Your doctor will advise you about when it may be possible for you to start driving again. This will usually be after a year free of seizures.

  • If you drink alcohol, ask your doctor for advice. Your doctor may advise you not to drink alcohol while you are on this medicine.

  • If you buy any medicines, check with a pharmacist that they are suitable for you to take with your antiepileptic medication.

  • You need to take zonisamide regularly every day. Do not stop taking it unless your doctor tells you to stop. Stopping treatment suddenly can cause problems and your doctor will want you to reduce your dose gradually if this becomes necessary.

Continue reading below

Can zonisamide cause problems?

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 zonisamide. 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 zonisamide side-effects (these affect more than 1 in 10 people)

What can I do if I experience this?

Feeling dizzy or sleepy; double vision

Do not drive and do not use tools or machines while affected

Lack of appetite, loss of weight, mood changes (such as being agitated or irritable, and depression), feeling unsteady or uncoordinated, poor memory or concentration

If any of these become troublesome, speak with your doctor for advice

Common zonisamide side-effects (these affect fewer than 1 in 10 people)

What can I do if I experience this?

Feeling sick (nausea), stomach upset, indigestion

Stick to simple meals - avoid rich and spicy food. Drink plenty of water to replace any lost fluids

Itchy rash or an allergic reaction; sharp back pain (which may indicate a kidney stone)

Speak with your doctor as soon as possible if you experience any of these

Bruising, feeling shaky, flu-like symptoms

If troublesome, speak with your doctor for advice

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

How to store zonisamide

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

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

  • The oral liquid medicine keeps for one month after first opening. After this time make sure you use a new bottle. It is a good idea to write the date you opened the bottle on the label.

Important information about all medicines

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.

If you are having an operation or dental treatment, tell the person carrying out the treatment which medicines you are taking.

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.

MHRA - Reporting adverse reactions

Report suspected side effects to medicines, vaccines, e-cigarettes, medical device incidents, defective or falsified (fake) products to the Medicines and Healthcare products Regulatory Agency to ensure safe and effective use.

Further reading and references

Article History

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

symptom checker

Feeling unwell?

Assess your symptoms online for free