Topiramate is a medicine used to treat epilepsy. These are also called anti-epileptic medicines.

It can also be taken to prevent migraine.

This medicine is only available on prescription. It comes as tablets or capsules.

• It's usual to take topiramate twice a day. You can take it with or without food.
• Common side effects of topiramate include feeling sleepy, dizziness, diarrhoea and feeling sick. These are usually mild and go away by themselves.
• If taking topiramate for epilepsy, it usually takes a couple of weeks for it to work. If taking topiramate to prevent migraines, it can take up to 3 months for it to work fully.
• Topiramate is also called by the brand name Topamax.

Topiramate can be taken by adults and children aged 2 years and over.

Topiramate is not suitable for some people.

Tell your doctor before starting the medicine if you:

• have ever had an allergic reaction to topiramate or any other medicines in the past
• have kidney problems, especially kidney stones
• have a blood disorder called acute porphyria
• have a history of blood metabolic acidosis, where the body produces too much acid or cannot remove it properly
• have eye problems, especially glaucoma
• have liver problems
• need to take high doses of vitamin C or calcium supplements
• are pregnant

Topiramate is a prescription medicine.

It's important to take it as instructed by your doctor.

How much will I take?

How much you take will depend on what you're using topiramate for.

It's usual to start topiramate at a low dose of 25mg to 50mg a day.

This will be increased over several weeks to the usual doses for:

• epilepsy - 100mg to 200mg a day, taken as 2 doses
• epilepsy (if you take another epilepsy medicine with topiramate) - 200mg to 400mg a day, taken as 2 doses
• migraines - 50mg to 100mg, taken as 2 doses

In children, the dose of topiramate will depend on the weight of your child.

Your doctor will be able to give the right dose to your child.

How to take it

It's usual to take topiramate twice a day. You can take topiramate at any time of day, but try to take your doses at the same time each day.

Try to space your doses evenly through the day. For example, first thing in the morning and in the evening.

Topiramate tablets can be taken with or without food. Swallow your tablets whole with a glass of water. Do not chew them.

Topiramate capsules can be swallowed whole or they can be opened and sprinkled on a teaspoon of soft food, like porridge or yoghurt.

What if I forget to take it?

If you forget to take a dose, take one as soon as you remember.

If it's less than 8 hours before the next dose is due, it's better to leave out the missed dose and take your next dose as normal.

Do not take 2 doses at the same time to make up for a forgotten dose.

If you forget doses often, it may help to set an alarm to remind you.

You could also ask your pharmacist for advice on other ways to help you remember to take your medicine.

What if I take too much?

Ask your doctor for advice straight away. Taking too much topiramate by accident can lead to serious side effects.

Like all medicines, topiramate can cause side effects, although not everyone gets them.

Common side effects

These common side effects may happen in more than 1 in 100 people. They're usually mild and go away by themselves.

Keep taking the medicine, but talk to your pharmacist or doctor if these side effects bother you or do not go away:

• feeling sick (nausea)
• feeling sleepy, dizzy or tired
• diarrhoea
• feeling depressed
• loss of appetite or weight loss

Serious side effects

Serious side effects are rare and happen in less than 1 in 10,000 people.

Tell your doctor straight away if you:

• get blurred vision, have difficulty seeing and eye pain – these can be signs of glaucoma; these symptoms usually occur during the first month of starting topiramate
• get pain in your back, belly or side, a burning sensation when you pee, cloudy or smelly pee – these are signs of kidney stones
• feel sleepy, lose your appetite, have an irregular heartbeat and faint – these can be signs of metabolic acidosis
• think your children are not sweating – some children taking topiramate may not sweat enough in hot weather, causing their body temperatures to rise

Serious allergic reaction

In rare cases, it's possible to have a serious allergic reaction (anaphylaxis) to topiramate.

These are not all the side effects of topiramate.

For a full list, see the leaflet inside your medicines packet.

What to do about:

• feeling sick - stick to simple meals and do not eat rich or spicy food. It might help to take your topiramate after a meal or snack.
• feeling sleepy, dizzy or tired - do not drive or use tools or machinery. Try to avoid drinking alcohol, as this will make you feel more tired. If you feel dizzy, stop what you're doing and sit or lie down until you feel better. As your body gets used to topiramate, these side effects should wear off. If they do not after a few weeks or you feel dizzy all the time, speak to your doctor.
• diarrhoea - drink lots of fluids, such as water or squash, to avoid dehydration. Signs of dehydration include peeing less than usual or having strong-smelling pee. Do not take any other medicines to treat diarrhoea without speaking to a pharmacist or doctor.
• feeling depressed - if this continues, speak to your doctor.
• loss of appetite or weight loss - try to eat at usual meal times even if you do not feel hungry. If this becomes a problem, speak to your doctor or pharmacist.

There's no firm evidence that topiramate is harmful to an unborn baby.

But for safety your doctor will only advise you to take it in pregnancy if the benefits of the medicine outweigh the risks.

It's important for you and your baby to stay well during pregnancy.

If you become pregnant while taking topiramate, tell your doctor or nurse straight away.

Do not stop taking it without talking to your doctor first.

If you have epilepsy, it's very important that it's treated during pregnancy as fits (seizures) can harm you and your unborn baby.

If you're pregnant, or trying to get pregnant, and taking topiramate, you're recommended to take a higher dose of folic acid, a vitamin that helps your baby grow normally.

Your doctor might prescribe a high dose of 5mg a day for you to take while you're trying to get pregnant and during the first 12 weeks of pregnancy.

For more information about how topiramate can affect you and your baby during pregnancy, read the leaflet about the best use of medicines in pregnancy (BUMPS).

Topiramate and breastfeeding

If your doctor or health visitor says your baby is healthy, topiramate can be taken while you're breastfeeding.

Topiramate passes into breast milk, but it's unlikely to cause any side effects in your baby.

It's been linked with side effects in very few breastfed babies.

If you notice that your baby's not feeding as well as usual, or seems unusually sleepy, or you have any other concerns about them, talk to your pharmacist, health visitor or doctor as soon as possible.

There are some medicines that may interfere with the effects of topiramate.

Tell your doctor if you're taking any of these medicines:

• medicines used to treat diabetes, such as metformin, glibenclamide and pioglitazone
• medicines used to treat depression or anxiety, such as venlafaxine and amitriptyline
• medicines for heart or blood pressure, such as diltiazem, hydrochlorothiazide and propranolol
• antipsychotic medicines, such as risperidone
• any other epilepsy medicines

Mixing topiramate with herbal remedies and supplements

Do not take St John's wort, the herbal remedy for depression, while you're being treated with topiramate.

This is because St John's wort may make topiramate less effective.