How does it work?

Topamax tablets and sprinkle capsules contain the active ingredient topiramate, which is a medicine that is used to treat epilepsy. Topiramate is also available without a brand name, ie as the generic medicine.

The brain and nerves are made up of many nerve cells which communicate with each other through electrical signals. These signals must be carefully regulated for the brain and nerves to function properly. When abnormally rapid and repetitive electrical signals are released in the brain, the brain becomes over-stimulated and normal function is disturbed. This results in fits or seizures.

Topiramate works in three ways to prevent epileptic fits. Firstly, it enhances the activity of a neurotransmitter called GABA in the brain. Neurotransmitters are chemicals that are stored in nerve cells and are involved in transmitting messages between the nerve cells. GABA is a neurotransmitter that acts as a natural calming agent. It keeps the nerve activity in the brain in balance. As topiramate enhances the action of GABA, it helps calm the nerve activity in the brain.

Topiramate also prevents sodium from entering the nerve cells when they begin to fire rapid and repetitive electrical signals. A build up of sodium in the nerve cells is necessary for the electrical signal to build up and be passed on. Topiramate therefore prevents the excessive electrical activity that causes fits.

Topiramate also decreases the ability of a neurotransmitter called glutamate to excite the nerve cells. It does this by blocking glutamate receptors.

All these actions calm the nerve cells and stabilise the electrical nerve activity in the brain. This helps maintain normal brain function and prevent fits.

Topiramate is also prescribed to prevent migraine headaches in adults, for example, for those who have three or more migraine attacks per month, or frequent migraines that significantly interfere with daily routine. It is not fully understood how topiramate works to prevent migraines. The medicine has to be taken continuously to prevent migraines. It is not intended for treating individual migraine attacks.

What is it used for?

• Epilepsy. Topamax is used to treat generalised tonic-clonic seizures (grand mal epilepsy) and partial seizures.
• Type of severe childhood epilepsy (Lennox-Gastaut syndrome).
• Prevention of migraine in adults.

Warning!

• Topamax tablets should be swallowed whole, not broken. Topamax capsules can be swallowed whole, or can be opened and the contents sprinkled on a teaspoon of soft food, such as mashed banana, apple sauce, ice cream or yoghurt. If you do this, the food and medicine mixture should be swallowed immediately without chewing. It should not be kept for later use.
• This medicine may cause drowsiness and problems with concentration. If affected do not drive or operate machinery. Drinking alcohol is likely to increase any drowsiness.
• It is important to drink plenty of water while taking this medicine, particularly in warm environments or when exercising. This is because topiramate has been reported to reduce sweating on rare occasions and this could cause flushing and raised body temperature. Drinking water helps keep the body cool. It is especially important to make sure children taking this medicine get enough fluid, as the majority of cases of raised temperature have been in children.
• Topiramate may increase the risk of kidney stones, particularly if you have a personal or family history of kidney stones, or if you are taking other medicines that have this side effect. Drinking plenty of water also reduces the risk of developing kidney stones.
• There may be a small increased risk of suicidal thoughts and behaviour in people taking antiepileptic medicines such as topiramate for any condition. For this reason, it is very important to seek medical advice if you, or someone else taking this medicine, experience any changes in mood, distressing thoughts, or feelings about suicide or self-harm at any point while taking this medicine. For more information speak to your doctor or pharmacist.
• Rarely, this medicine may cause raised pressure in the eye (closed angle glaucoma). If you experience sudden eye pain or redness, or blurring of your vision, particularly in the first few weeks of treatment, then consult your doctor immediately. If you do have raised pressure in the eye, you will need to stop treatment with this medicine and start treatment to lower the pressure in your eye. Your doctor will explain more.
• This medicine can cause loss of appetite and weight loss. You should be weighed regularly during treatment. If you are losing too much weight, or a child taking this medicine is not gaining enough weight, your doctor will ask you to increase the amount of food being eaten, or may prescribe dietary supplements.
• This medicine may rarely cause skin reactions. You should let your doctor know if you develop a rash, skin peeling, itching, or other unexplained skin reaction while taking this medicine.
• If you are taking an oral contraceptive at the same time as this medicine you should tell your doctor if you experience any changes in your menstrual bleeding, because this may mean that your contraceptive is becoming less effective at preventing pregnancy.
• If you have epilepsy it is important to take your medication regularly, as directed by your doctor, because missing doses can trigger seizures in some people. If you have trouble remembering to take your medicine you should ask your pharmacist for advice. You may find a pill reminder box helpful.
• You should not stop taking this medicine suddenly unless your doctor tells you otherwise, as this may result in your seizures or migraines returning or getting worse. If it is decided that you should stop taking this medicine, it should be withdrawn gradually, according to the instructions given by your doctor.

Use with caution in

• Decreased liver function.
• Decreased kidney function.
• Personal or family history of kidney stones.
• High levels of calcium in the urine (hypercalciuria).
• History of depression or suicidal thoughts.
• Adolescents and young adults.
• Severe lung/breathing disorders.
• Hereditary blood disorders called porphyrias.

Not to be used in

• Epilepsy in children under two years of age.
• Migraine in children under 16 years of age.
• Breastfeeding.
• Rare hereditary problems of galactose intolerance, the Lapp lactase deficiency or glucose-galactose malabsorption.

This medicine should not be used if you are allergic to any of its ingredients. Please inform your doctor or pharmacist if you have previously experienced such an allergy.

If you feel you have experienced an allergic reaction, stop using this medicine and inform your doctor or pharmacist immediately.

Pregnancy and breastfeeding

Certain medicines should not be used during pregnancy or breastfeeding. However, other medicines may be safely used in pregnancy or breastfeeding providing the benefits to the mother outweigh the risks to the unborn baby. Always inform your doctor if you are pregnant or planning a pregnancy, before using any medicine.

• It is very important for women with epilepsy to talk to the doctor responsible for their epilepsy treatment before becoming pregnant. Antiepileptic medicines are associated with an increased risk of developmental disorders and malformations in the baby. However, stopping antiepileptic treatment during pregnancy runs the risk of the mother having seizures, which can harm both the mother and the foetus. This risk may be higher than that from continuing the medication. It is important that all the risks and benefits of treatment are weighed up. Seek medical advice from your doctor.
• The safety of this medicine for use during pregnancy has not been established. It should not be used during pregnancy unless, in the opinion of the doctor, the potential benefit outweighs the potential risk to the foetus.
• This medicine may pass into breast milk. It should not be used by breastfeeding mothers. Mothers who need treatment with this medicine should bottlefeed their infants. Seek medical advice from your doctor.

Label warnings

• This medication may cause drowsiness. If affected do not drive or operate machinery.
• Do not stop taking this medication except on your doctor's advice.

Side effects

Medicines and their possible side effects can affect individual people in different ways. The following are some of the side effects that are known to be associated with this medicine. Just because a side effect is stated here does not mean that all people using this medicine will experience that or any side effect.

• Pins and needles sensation (paraesthesia).
• Headache.
• Fatigue.
• Dizziness.
• Drowsiness.
• Decreased appetite and weight loss.
• Nausea.
• Difficulty sleeping (insomnia).
• Depression.
• Concentration or memory difficulties.
• Abdominal pain.
• Nervousness.
• Decreased sense of touch.
• Confusion.
• Agitation.
• Visual disturbances.
• Speech disturbances.
• Shaky movements and unsteady walk (ataxia).
• Weakness or loss of strength (asthenia).
• Alteration in taste.
• Behaviour problems in children.
• Increased acid levels in the blood (metabolic acidosis).

The side effects listed above may not include all of the side effects reported by the medicine's manufacturer.

For more information about any other possible risks associated with this medicine, please read the information provided with the medicine or consult your doctor or pharmacist.

How can this medicine affect other medicines?

It is important to tell your doctor or pharmacist what medicines you are already taking, including those bought without a prescription and herbal medicines, before you start treatment with this medicine. Similarly, check with your doctor or pharmacist before taking any new medicines while taking this one, to ensure that the combination is safe.

The amount of topiramate in the blood may be decreased by the following medicines:

• carbamazepine
• phenobarbital
• phenytoin
• primidone.

Topiramate may increase the blood level of phenytoin, and people taking this combination of antiepileptic medicines should have the amount of phenytoin in their blood monitored.

It is recommended that people who are taking any antiepileptic medicines should avoid taking the herbal remedy St John's wort (Hypericum perforatum). This is because St John's wort may affect the level of antiepileptic medicines in the blood and could increase the risk of seizures.

Topiramate may make combined oral contraceptive pills less effective by reducing the blood level of oestrogen. For this reason, women using combined oral contraceptives should be prescribed a pill(s) containing at least 50 micrograms of oestrogen. Alternatively, non-hormonal methods of contraception such as condoms should be used to prevent pregnancy. If you are taking an oral contraceptive with topiramate you should tell your doctor if you experience any changes in your menstrual bleeding, because this may mean that your pill is becoming less effective at preventing pregnancy.

There may be an increased risk of drowsiness and sedation if this medicine is taken with any of the following (which can also cause drowsiness):

• alcohol
• barbiturates, eg phenobarbital
• benzodiazepines, eg diazepam
• sedating antihistamines, eg chlorphenamine
• sleeping tablets
• strong opioid painkillers, eg morphine, codeine
• tricyclic antidepressants, eg amitriptyline.

Other medicines containing the same active ingredient

Topiramate tablets are also available without a brand name, ie as the generic medicine.