Zonisamide for epilepsy (Zonegran)

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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.

Type of medicineAn antiepileptic medicine
Used forEpilepsy in adults and children over 6 years of age
Also calledZonegran®
Available asCapsules

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.

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 are pregnant, trying for a baby or breast-feeding.
  • If you are taking any other medicines. This includes any medicines you are taking which are available to buy without a prescription, such 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.
  • 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.
  • 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.
  • 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.
  • 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 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.

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 visionDo not drive or 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 concentrationIf any of these become troublesome, speak with your doctor for advice
Common zonisamide side-effects (these affect less than 1 in 10 people)What can I do if I experience this?
Feeling sick, stomach upset, indigestionStick 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 symptomsIf 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.

  • 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.

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.

Further reading & references

  • Manufacturer's PIL, Zonegran® capsules; Eisai Ltd, The electronic Medicines Compendium. Dated October 2013.
  • British National Formulary; 68th Edition (Sep 2014) British Medical Association and Royal Pharmaceutical Society of Great Britain, London

Disclaimer: This article is for information only and should not be used for the diagnosis or treatment of medical conditions. EMIS has used all reasonable care in compiling the information but make no warranty as to its accuracy. Consult a doctor or other health care professional for diagnosis and treatment of medical conditions. For details see our conditions.

Original Author:
Helen Allen
Current Version:
Peer Reviewer:
Dr John Cox
Document ID:
4120 (v29)
Last Checked:
Next Review:
The Information Standard - certified member

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