ANTI-EPILEPTIC DRUGS

by Epilepsy Association of Scotland

Anti-epileptic therapy currently enables over 70% of people with epilepsy to live free of seizures. In the last few years three new drugs have become available, and there are a further four or five at an advanced stage of research.

Purpose

The purpose of drug treatment is to control (but not cure) epilepsy, by preventing seizures without producing undesirable side-effects. Reaching this balance may take several months or even longer. During this period some people will experience adverse symptoms that can make them lose heart. In others, control of seizures will never be fully gained. It is important for these people to continue with treatment, and to keep a careful note of seizure numbers and side-effects. This record will help the doctor make the best decision, particularly if it becomes necessary to change the dose or to try another drug.

Alternative treatment

Anti-epileptic drugs are the mainstay of treatment for epilepsy. Occasionally (for instance, in young children with very severe epilepsy) a special diet may be helpful. For a few people, surgery will be advised.

Common anti-epileptic drugs

There are a number of established drugs that are commonly prescribed. These can be referred to by their chemical name, or by the manufacturer's trade name (in brackets), as follows:

• Carbamazepine (Tegretol)
• Clobazam (Frisium)
• Clonazepam (Rivotril)
• Ethosuximide (Zarontril)
• Phenobarbitone
• Phenytoin (Epanutin)
• Primidone (Mysoline)
• Sodium Valproate (Epilim)

Rectal diazepam (Stesolid) may be prescribed to prevent a series of seizures or, occasionally, status epilepticus. Parents and other carers can also administer this formulation to stop a child having a febrile convulsion.

New drugs

Over the past few years, three new drugs, vigabatrin (Sabril), lamotrigine (Lamictal), and gabapentin (Neurontin) have been launched in this country. These are used mainly as additional treatment, i.e. they are taken in conjunction with other anti-epileptic drugs by people who are still experiencing seizures despite receiving one or more of the established drugs. Because they are so new, it is likely that all their side-effects are still not known. In addition, they cost quite a bit more than the older drugs. Nevertheless, they are very effective in many cases, and represent hope for the future. There are even more new drugs on the way, such as oxcarbazepine, felbamate, topiramate and tiagabine.

Mode of action

Anti-epileptic drugs are absorbed into the body and carried in the blood to the brain, where they dampen down the tendency for the development of the "electrical storms" that are seizures. Control is helped by maintaining a roughly constant amount of drug in the bloodstream throughout the day and night. Missed doses reduce the blood level, and can result in more seizures. Too much medication can, surprisingly, sometimes also produce an increase in seizures. It is important, therefore, that the same amount of drug is taken each day. The exact timing of every dose is not as important.

Side-effects

Anti-epileptic drugs are not addictive, but they sometimes cause side-effects. These can include tiredness, double vision, nausea, headache, weight gain, temporary hair loss, skin rash, swollen gums, tremor of the fingers, and unsteadiness. Some adverse effects can be minimised by adjusting the dose of the medication. Good dental hygiene can prevent swollen gums. Correct timing of doses can ensure that tiredness occurs only at night. Watching the diet will help to avoid a gain in weight. The appearance of a skin rash should be reported immediately to your doctor.

Women who take anti-epileptic medication and who wish to use some form of oral contraception should seek medical advice, as many anti-epileptic drugs can reduce the effectiveness of the contraceptive pill. Exceptions are sodium valproate (Epilim) and clonazepam (Rivotril), and the newer drugs vigabatrin (Sabril), lamotrigine (Lamictal), and gabapentin (Neurontin).

Women on anti-epileptic medication, who want to have a baby, should ideally consult their doctor before becoming pregnant, as there may be a small risk to the baby from their treatment. Changing or reducing the anti-epileptic drugs prior to pregnancy may be advised. A woman who is already pregnant should discuss with her doctor the best course of action, in order to minimise the risks both to herself and to her baby. The dose of anti-epileptic drugs should not be substantially altered in early pregnancy, as it is particularly important to keep the number of seizures as low as possible to avoid harming the unborn child.

Choice of drug

The benefits of good seizure control must be balanced against the disadvantages of any side-effects when choosing the correct drug and deciding on the dose. There are many factors that can influence the doctor's choice. The type of seizures, medical history, and other medication, are all taken into consideration. The doctor must also decide which form of the drug is most suitable for each patient to take.

Tablets are usually prescribed. However, syrups can be used for children who have difficulty in swallowing tablets. Changes in the make of the usual tablet or capsule should be avoided, since the amount of drug absorbed from different kinds of pills can vary.

Dosage

The most effective amount for controlling seizures varies from person to person. However, the correct dose of the right drug (or in some cases, the right combination of two or more drugs) will completely control seizures in the majority of cases, without any side-effects. As children grow up, their dose may need to be increased. A bigger dose may also be advised if seizures are not fully abolished, and also sometimes in late pregnancy. Consult a doctor if your seizure control is unexpectedly poor, or if drug side-effects become a problem.

Measuring drug level

Occasionally, measuring the drug level in the blood can be helpful. This depends on the drug, how effective it is, and whether there are side-effects. The person's medical history and the number of other drugs being taken are also relevant factors in making this decision. Because some people metabolise anti-epileptic drugs more quickly than others, a blood test may be recommended to ensure that the best dose is being prescribed. A few drops of blood can reveal whether the dose is too low to be effective, or too high and likely to cause unpleasant side-effects.

If seizures are fully controlled without any side-effects it is not necessary to measure the drug level. Drug levels of the newer drugs vigabatrin (Sabril), lamotrigine (Lamictal) and gabapentin (Neurontin) are not helpful.

Missed doses

The importance of taking drugs at regular intervals cannot be over emphasised. However, it is not easy for everyone to remember to take the correct dose at the same time each day, particularly if he or she has a poor memory. The answer may be to set aside the tablets each morning, so that a check can be made in the evening that the full amount has been taken.

Ri-Med Medical Appliances, 82 Whitby Crescent, Woodthorne, Nottingham NG5 4LZ make the "Dosett", which helps people to take their medicine in the correct dose and at the right time. This device consists of a small box divided into seven sections, one for every day of the week. Each section is subdivided into four compartments, allowing up to four daily doses to be held.

An alarm wrist watch can also be used to remind a person when to take his or her medication. If a dose is forgotten, it should be taken at the usual time. This may make the person feel a little dopey for a while, but helps to prevent a seizure occurring.

Extra medication should not be taken after a seizure. If medication has been missed, it is unwise to take part in potentially dangerous activities such as driving or swimming. If occasional nights are spent away from home, missed doses can be avoided by carrying a spare dose or two to cover unexpected circumstances.

When holidaying abroad, it is important to take a supply of your drugs with you sufficient to cover the period away from home, as it may not always be possible to get the same drug, tablets or capsules in a foreign country. Ask our doctor for a list of available drugs and their different trade names in other parts of the world.

Length of treatment

The length of treatment necessary varies with each individual case of epilepsy. Some people will need to take medication throughout their life. However, it may be possible for a few people who have been free of seizures for two years to have their medication slowly withdrawn under medical supervision.

Most doctors (and patients), however, prefer to wait for five years, as the risk of having a further seizure once off medication is substantially less. It is important that treatment is never altered or stopped, except by a doctor. Making changes without medical advice may lead to prolonged or repeated seizures, which can prove dangerous.

Other precautions

Most children like to mimic the activities of adults and they may be tempted to copy a parent who takes tablets every day. All medication should be stored out of reach of children and kept in child-proof containers.

Alcohol interferes with the effectiveness of anti-epileptic drugs. It is advisable to avoid it altogether, or consume it only in modest amounts. Glass bottles may break during a seizure, and should not be carried. Most chemists now supply plastic bottles.

However frustrating it may be to take medication for a long period, it is important to comply with the prescribed drug treatment if seizures are to be fully controlled.

The future

Advances in the understanding of the neurochemical basis of epilepsy, and research into the development of new anti-epileptic drugs, will contribute in future to better seizure control for even more people with epilepsy.