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Zonisamide 50mg Hard Capsules

Active Ingredient:
Glenmark Pharmaceuticals Europe Ltd See contact details
ATC code: 
About Medicine
The Patient Information Leaflet (PIL) is the leaflet included in the pack with a medicine.
Last updated on emc: 26 Apr 2023

Below is a text only representation of the Patient Information Leaflet (ePIL).

The text only version may be available in large print, Braille or audio CD. For further information call emc accessibility on {phone} 0800 198 5000. The product code(s) for this leaflet is: PL 25258/0182.

Zonisamide 25mg_50mg_100mg Hard Capsules

Package leaflet: Information for the user

Zonisamide Glenmark 25 mg hard capsules

Zonisamide Glenmark 50 mg hard capsules

Zonisamide Glenmark 100 mg hard capsules


Read all of this leaflet carefully before you start taking this medicine because it contains important information for you.
  • Keep this leaflet. You may need to read it again.
  • If you have any further questions, ask your doctor or pharmacist.
  • This medicine has been prescribed for you only. Do not pass it on to others. It may harm them, even if their signs of illness are the same as yours.
  • If you get any side effects talk to your doctor or pharmacist. This includes any possible side effects not listed in this leaflet. See section 4.

What is in this leaflet:

1. What Zonisamide Glenmark is and what it is used for
2. What you need to know before you take Zonisamide Glenmark
3. How to take Zonisamide Glenmark
4. Possible side effects
5. How to store Zonisamide Glenmark
6. Contents of the pack and other information

1. What Zonisamide Glenmark is and what it is used for

Zonisamide Glenmark contains the active substance zonisamide, and is used as an antiepileptic medicine.

Zonisamide is used to treat seizures that affect one part of the brain (partial seizure), which may or may not be followed by a seizure affecting all of the brain (secondary generalisation).

Zonisamide may be used:

  • On its own to treat seizures in adults.
  • With other antiepileptic medicines to treat seizures in adults, adolescents, and children aged 6 years and above.

2. What you need to know before you take Zonisamide Glenmark
Do not take Zonisamide:
  • If you are allergic to zonisamide or any of the ingredients in Zonisamide (listed in section 6),
  • If you are allergic to other sulphonamide medicines. Examples include: sulphonamide antibiotics, thiazide diuretics, and sulfonylurea antidiabetes medicines.

Warnings and precautions:

Zonisamide belongs to a group of medicines (sulphonamides) which can cause severe allergic reactions, severe skin rashes, and blood disorders, which very rarely can be fatal (see section 4 Possible side effects).

Serious rashes occur in association with Zonisamide therapy, including cases of Stevens-Johnson syndrome.

The use of Zonisamide may lead to high levels of ammonia in the blood which could lead to a change in brain function, especially if you are also taking other medicines which can increase ammonia levels (for example valproate), have a genetic disorder causing build-up of too much ammonia in the body (urea cycle disorder), or if you have liver problems. Tell your doctor immediately if you become unusually drowsy or confused.

Talk to your doctor or pharmacist before taking Zonisamide if you:

  • are younger than 12 years old, as you may be at greater risk of decreased sweating, heat stroke, pneumonia and liver problems. If you are younger than 6 years old, Zonisamide is not recommended for you.
  • are elderly, as your dose of Zonisamide may need adjusting, and you may be more likely to develop an allergic reaction, severe skin rash, swelling of the feet and legs, and itchiness when taking Zonisamide (see section 4 Possible Side Effects).
  • suffer from liver problems, as your dose of Zonisamide may need adjusting.
  • have eye problems such as glaucoma.
  • suffer from kidney problems as your dose of Zonisamide may need adjusting.
  • have previously suffered from kidney stones, as you may be at increased risk of developing more kidney stones. Reduce the risk of kidney stones by drinking sufficient water.
  • live in a place or are on holiday in a place where the weather is warm. Zonisamide can make you perspire less, which can cause your body temperature to increase. Reduce the risk of overheating by drinking sufficient water and keeping cool.
  • are underweight, or have lost a lot of weight as Zonisamide can cause you to lose more weight. Tell your doctor as this may need to be monitored.
  • are pregnant or could become pregnant (see section ‘pregnancy, breast-feeding and fertility’ for further information).

If any of these applies to you, tell your doctor before you take Zonisamide

Children and adolescents

Talk to your doctor about the following risks:

Preventing overheating and dehydration in children

Zonisamide can cause your child to sweat less and overheat and if your child is not treated this can lead to brain damage and death. Children are most at risk especially in hot weather.

When your child is taking Zonisamide: Keep your child cool especially in hot weather

  • Your child must avoid heavy exercise especially when the weather is hot
  • Give your child plenty of cold water to drink
  • Your child must not take these medicines:
  • Carbonic anhydrase inhibitors (like topiramate and acetazolamide), and anticholinergic agents (like clomipramine, hydroxyzine, diphenhydramine, haloperidol, imipramine and oxybutynin).

If your child’s skin feels very hot with little or no sweating, becomes confused, has muscle cramps, or your child’s heartbeat or breathing becomes rapid:

  • Take your child to a cool, shaded place
  • Sponge your child’s skin with cool (not cold) water
  • Give your child cold water to drink
  • Seek urgent medical assistance.

  • Body weight: You should monitor your child’s weight every month and see your doctor as soon as possible if your child is not gaining enough weight. Zonisamide is not recommended for children who are underweight or have a small appetite, and should be used with caution in those below 20 kg.
  • Increased acid level in the blood and kidney stones: Reduce these risks by ensuring that your child drinks enough water and is not taking any other medicine which could cause kidney stones (see Other medicines). Your doctor will monitor your child’s blood bicarbonate levels and kidneys (see also section 4).

Do not give this medicine to children below the age of 6 years because it is not known for this age group whether the potential benefits are greater than the risks.

Other medicines and Zonisamide

Tell your doctor or pharmacist if you are taking, have recently taken or might take any other medicines obtained without a prescription.

  • Zonisamide should be used carefully in adults when taken with medicines that can cause kidney stones, like topiramate or acetazolamide. In children, this combination is not recommended
  • Zonisamide could possibly increase your blood levels of medicines like digoxin and quinidine, and so a reduction in their dose may be required.
  • Other medicines like phenytoin, carbamazepine, phenobarbitone and rifampicin can decrease your blood levels of Zonisamide, which may require an adjustment of your dose of Zonisamide.

Zonisamide with food and drink

Zonisamide can be taken with or without food.

Pregnancy, breastfeeding and fertility

If you are planning a pregnancy, talk to your doctor before you stop contraception and before you become pregnant about the possibility of switching to other suitable treatments. If you are or think you might be pregnant, tell your doctor straight away. You should not stop your treatment without discussing this with your doctor. Suddenly stopping may lead to breakthrough seizures which may harm you and your unborn baby. It is important that your epilepsy remains well controlled.


You must only take Zonisamide during your pregnancy if your doctor tells you to. If you are a woman of childbearing age you must use adequate contraception while taking and for one month after stopping Zonisamide.

Studies have shown an increased risk of physical birth abnormalities in children of women taking epilepsy medicines during pregnancy. The risk of birth defects or neurodevelopmental disorders (problems with brain development) for your child after taking Zonisamide during your pregnancy is unknown. The risk of physical birth abnormalities may increase when more than one epilepsy medicine is used at the same time. Where possible, your doctor should consider using one epilepsy medicine to control your epilepsy. More research is needed to better understand whether taking zonisamide during pregnancy increases the risk of having a baby born with a physical birth abnormality or a learning or thinking disability.

Studies have shown that babies born to mothers using zonisamide during pregnancy were smaller than expected for their age at birth, compared with babies born to mothers treated with lamotrigine monotherapy. Make sure you are fully informed about the risks and the benefits of using zonisamide for epilepsy during pregnancy.

Do not breastfeed whilst taking, or for one month after stopping Zonisamide.

There are no clinical data available on the effects of Zonisamide on human fertility. Studies in animals have shown changes in fertility parameters.

Driving and using machines

Zonisamide may affect your concentration, ability to react/respond, and may make you feel sleepy, particularly at the beginning of your treatment or after your dose is increased. Be especially careful while driving or operating machinery, if Zonisamide affects you in this way.

3. How to take Zonisamide Glenmark

Always take Zonisamide Glenmark exactly as your doctor has told you. You should check with your doctor or pharmacist if you are not sure.

The usual adult dose

When you take Zonisamide on its own:

  • The starting dose is 100 mg taken once a day.
  • This may be increased by up to 100 mg at intervals of two weeks.
  • The usual dose is 300 mg once a day.

When you take Zonisamide with other antiepileptic medicines:

  • The starting dose is 50 mg daily taken in two equal doses of 25 mg.
  • This may be increased by up to 100 mg at intervals of one to two weeks.
  • The usual daily dose is between 300 mg and 500 mg.
  • Some people respond to lower doses. The dose may be increased more slowly if you experience side effects, are elderly or if you suffer from kidney or liver problems.

Use in children (aged 6 to 11 years) and adolescents (aged 12 to 17 years) weighing at least 20 kg:
  • The starting dose is 1 mg per kg of body weight taken once a day.
  • This may be increased by 1 mg per kg of body weight at intervals of one to two weeks.
  • The usual daily dose is 6 to 8 mg per kg for a child with a body weight of up to 55 kg or 300 to 500 mg for a child with a body weight more than 55 kg (which ever dose is lower) taken once a day.

Example: A child who weighs 25 kg should take 25 mg once a day for the first week, and then increase the daily dose by 25 mg at the start of each week until a daily dose between 150 to 200 mg is reached.

If you feel that the effect of Zonisamide is too strong or too weak, talk to your doctor or pharmacist.

How and when to take the capsules
  • Zonisamide capsules must be swallowed whole with water.
  • Do not chew the capsules.
  • Zonisamide can be taken once or twice daily, as instructed by your doctor.
  • If you take Zonisamide twice a day, take half the daily dose in the morning and half in the evening.

If you take more Zonisamide than you should

If you may have taken more Zonisamide than you should, tell a carer (relative or friend), your doctor or pharmacist immediately, or contact your nearest hospital casualty department, taking your medicine with you. You may become sleepy and could lose consciousness. You might also feel sick, have a sore stomach, muscle twitches, eye movement, feel faint, have a slowed heartbeat, and reduced breathing and kidney function. Do not try to drive.

If you forget to take Zonisamide
  • If you forget to take a dose, don’t worry: take the next dose when it is due.
  • Do not take double the dose to make up for the forgotten dose.

If you stop taking Zonisamide
  • Zonisamide is meant to be taken as a long-term medicine. Do not reduce your dose or stop your medicine unless your doctor tells you to.
  • If your doctor advises you to stop taking Zonisamide your dose will be reduced gradually to lower the risk of more seizures.

If you have any further questions on the use of this product, ask your doctor or pharmacist.

4. Possible side effects

Like all medicines, Zonisamide can cause side effects, although not everybody gets them.

Zonisamide belongs to a group of medicines (sulphonamides) that can cause severe allergic reactions, severe skin rashes, and blood disorders, which very rarely can be fatal.

Contact your doctor immediately if you:
  • have difficulty breathing, a swollen face, lips or tongue, or a severe skin rash as these symptoms may indicate that you are having a severe allergic reaction.
  • have signs of overheating - high body temperature but little or no sweating, rapid heartbeat and breathing, muscle cramps, and confusion.
  • have thoughts of harming or killing yourself. A small number of people being treated with anti- epileptics such as Zonisamide have had thoughts of harming or killing themselves.
  • have pain in your muscles or a feeling of weakness, as this may be a sign of abnormal muscle breakdown which can lead to kidney problems.
  • get a sudden pain in your back or stomach, have pain on urinating (passing water) or notice blood in your urine, as this may be a sign of kidney stones.
  • develop visual problems such as eye pain or blurred vision while taking Zonisamide.

Contact your doctor as soon as possible if you:
  • have an unexplained skin rash, as this could develop into a more severe skin rash or skin peeling.
  • feel unusually tired or feverish, have a sore throat, swollen glands, or find that you bruise more easily, as this may mean you have a blood disorder.
  • have signs of increased acid level in the blood- headaches, drowsiness, shortness of breath and loss of appetite. Your doctor may need to monitor or treat this.

Your doctor may decide that you should stop using Zonisamide.

The most common side effects of Zonisamide are mild. They occur during the first month of treatment and usually decrease with continued treatment. In children ages 6 – 17 years old, side effects were consistent with those described below with the following exceptions: pneumonia, dehydration, sweating decreased (common) and abnormal liver enzymes (uncommon).

Very common side effects (may affect more than 1 in 10 people)

  • agitation, irritability, confusion, depression
  • poor muscle coordination, dizziness, poor memory, sleepiness, double vision
  • loss of appetite, decreased blood levels of bicarbonate (a substance that prevents your blood from becoming acidic)

Common side effects (may affect up to 1 in 10 people)

  • difficulty sleeping, strange or unusual thoughts, feeling anxious or emotional.
  • slowed thoughts, loss of concentration, speech abnormalities, abnormal skin sensation (pins and needles), tremor, involuntary movement of the eyes.
  • kidney stones.
  • skin rashes, itching, allergic reactions, fever, tiredness, flu-like symptoms, hair loss.
  • ecchymosis (a small bruise caused by blood leaking from broken blood vessels in the skin).
  • loss of weight, nausea, indigestion, stomach pains, diarrhoea (loose stools), constipation.
  • swelling of the feet and legs.

Uncommon side effects (may affect up to 1 in 100 people)

  • anger, aggression, thoughts of suicide, suicide attempt.
  • vomiting.
  • gall bladder inflammation, gallstones.
  • urinary stones.
  • lung infection / inflammation, urinary tract infections.
  • low blood potassium levels, convulsions/seizures.

Very rare side effects (may affect up to 1 in 10,000 people)

  • hallucinations, memory loss, coma, neuroleptic malignant syndrome (inability to move, sweating, fever, incontinence), status epilepticus (prolonged or repeated seizures).
  • breathing disorders, shortness of breath, inflammation of the lungs.
  • inflammations of the pancreas (severe pain in the stomach or back)
  • liver problems, kidney failure, increased blood levels of creatinine (a waste product that your kidneys should normally remove). .
  • severe rashes or skin peeling (at the same time you may feel unwell or develop a fever).
  • abnormal muscle breakdown (you may feel pain or weakness in your muscles) which can lead to kidney problems.
  • swollen glands, blood disorders (reduction in the number of blood cells, which can make infection more likely and can make you look pale, feel tired and feverish, and bruise more easily).
  • decreased sweating, overheating.
  • glaucoma, which is a blockage of fluid in the eye causing increased pressure in the eye. Eye pain, blurred vision or decreased vision may occur and can be signs of glaucoma.

Reporting of side effects

If you get any side effects, talk to your doctor, pharmacist or nurse. This includes any possible side effects not listed in this leaflet. You can also report side effects directly via the Yellow Card Scheme or search for MHRA Yellow Card in the Google Pay or Apple App Store. By reporting side effects you can help provide more information on the safety of this medicine.

5. How to store Zonisamide Glenmark

Keep this medicine out of the sight and reach of children.

Do not use this medicine after the expiry date which is stated on the blister and the carton after EXP. The expiry date refers to the last day of that month.

This medicinal product does not require any special storage conditions.

Do not use if you notice any damage to the capsules, blister or carton or any visible signs of deterioration in the medicine. Return the pack to your pharmacist.

Do not throw away any medicines via wastewater or household waste. Ask your pharmacist how to throw away medicines you no longer require. These measures will help to protect the environment.

6. Contents of the pack and other information
What Zonisamide Glenmark contains

The active substance in Zonisamide Glenmark is zonisamide.

Zonisamide Glenmark 25 mg hard capsules contain 25 mg of zonisamide.

Zonisamide Glenmark 50 mg hard capsules contain 50 mg zonisamide.

Zonisamide Glemnmark 100 mg hard capsules contain 100 mg zonisamide.

  • The other ingredients that are present in the capsule contents are: microcrystalline cellulose, hydrogenated vegetable oil and sodium lauryl sulpfate. The printing ink contains schellac (E904), potassium hydroxide and iron oxide black (E172).
  • The capsule shell contains: gelatin, titanium dioxide (E171). Additionally the 50mg capsule shell contains iron oxide black (E172) and the 100mg capsule shell contains quinoline yellow (E104) and erythrosine (E127)..

What Zonisamide Glenmark looks like and contents of the pack
  • Zonisamide 25 mg hard capsules have an opaque white cap and body, imprinted with a 'G' and '742' , approximately 14.40±0.5 mm in length.
  • Zonisamide 50 mg hard capsules have an opaque grey cap and opaque white body, imprinted with a 'G' and '743', approximately 15.80±0.5 mm in length.
  • Zonisamide 100 mg hard capsules have an opaque red cap and opaque white body, imprinted with a 'G' and '744', approximately 19.20±0.5 mm in length..

Zonisamide capsules are packaged in blisters supplied in boxes containing: 14, 28, 56, 84, 98 and 196 hard capsules.

Not all pack sizes may be available.

Marketing Authorisation Holder
Glenmark Pharmaceuticals Europe Limited
Laxmi House
2-B Draycott Avenue
United Kingdom

Glenmark Pharmaceuticals Europe Limited
Building 2
Croxley Green Business Park
WD18 8YA

This leaflet was last revised in April 2023.

Glenmark Pharmaceuticals Europe Ltd
Company image
Building 2, Croxley Park, Watford, WD18 8YA
+44 (0)1923 202 950
+44 (0)1923 251137
Medical Information Direct Line
0800 458 0383
Stock Availability
+44 (0)1923 202 950