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Anti-seizure medication (ASM)

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Anti-seizure medication (ASM)

For most people with epilepsy, the main type of treatment is anti-seizure medication (ASM), previously called anti-epileptic drugs or AEDs. Up to 70% (7 in 10) of people could stop having seizures with the right medication.

An introduction to anti-seizure medication

For most people with epilepsy, the main type of treatment is anti-seizure medication (ASM), previously called anti-epileptic drugs or AEDs. Up to 70% (7 in 10) of people could stop having seizures with the right medication. This information is for both adults and children with epilepsy and answers some questions you might have about anti-seizure medication. Where we talk about controlling seizures or ‘seizure control’ we mean stopping seizures from happening.

What is anti-seizure medication (ASM) and what does it do?

Some medications are taken as a ‘course of treatment’ to cure a condition (for example, taking a course of antibiotics for an infection). Anti-seizure medication (ASM) is different; it is a preventative medication taken every day to try and stop seizures from happening. It does this by reducing the excessive electrical activity in the brain that causes seizures. The way ASM works is not completely understood, and it is likely that different ASMs work in slightly different ways.

What is the aim of treatment with ASM?

The aim of treatment is ‘optimal therapy’. This means taking the fewest types of ASMs, at the lowest dose in order to get the best seizure control possible with the fewest side effects. If optimal therapy cannot be found with one particular ASM there are usually several others that can be tried, alone or in combination.

When is treatment usually started?

Epilepsy is the tendency to have repeated seizures that start in the brain. Treatment is usually only considered after a diagnosis of epilepsy has been made. This is usually after someone has had repeated seizures.

In some rare situations treatment might be considered straightaway, after just a single seizure. This is usually only when a doctor thinks that it is very likely that you will have further seizures.

Who will be involved with my epilepsy care?

If you or your child have been diagnosed with epilepsy, it is likely that you will have seen a specialist - a neurologist for adults, or a paediatrician or paediatric neurologist for children. You may already have discussed treatment options with them. They will usually prescribe your ASM and arrange follow-up appointments to see how you are getting on.

The day-to-day management of your epilepsy might be under the care of your GP. For example, they might write your prescriptions. They should also have a copy of your treatment plan so you can talk to them about how you get on.

You might also see an epilepsy specialist nurse (ESN). ESNs work alongside the specialist and GP to help you manage your epilepsy. Not all hospitals have an ESN but you can ask about this at your local hospital.

In the longer term, if your seizures become controlled, you might only see your GP to review your epilepsy each year.

How is ASM chosen?

There are about 30 ASMs and each has a particular type or types of seizures that it works for. The choice of ASM firstly depends on the type of seizures you have, and which ASM works for these seizures. NICE has recommendations about which ASM should be used for different types of epilepsy and seizures.

When a drug is chosen, your specialist will take into account any other conditions you have or medication you take. As you may be on drugs for a number of years, they will consider not just what is right for you right now but also for the future. For example, when a girl is first prescribed ASM they will think about when she becomes an adult and may want to start a family.

Some ASM can affect an unborn baby while it is developing and so these drugs are usually avoided for girls and women who may become pregnant.

Although ASM recommendations are largely the same for men, women and children, there are some reasons why a particular ASM might be chosen or avoided for a particular person. This may be due to possible side effects.

Starting treatment

You are entitled to free prescriptions for your ASM and any other prescribed medication. 

Treatment is usually started with a 'first line' ASM. This is an ASM that is tried first and taken on its own, sometimes called monotherapy. Once the most appropriate ASM for you has been identified and discussed with you, you will usually start on a very low dose. This helps your body get used to the medication, and makes side effects less likely. The dose is then increased slowly over a number of weeks until it stops your seizures. The right dose for you may be different to what is right for someone else and is sometimes referred to as your ‘individual therapeutic concentration’.

How the body absorbs, uses and removes medication changes with age. For children, ASM doses are based on their body weight and so the dose increases as they get older (up to around 12 years of age). For adults, doses are not based on body weight.

For most people, once the right ASM for them is found, it will stop their seizures. Although for some people it can take time to get this right, the aim is to stop your seizures by just taking one ASM. However, if your seizures do not stop when the dose is increased, or you start to have side effects, you may want to talk to your doctor about changing to a different ASM. Because different ASMs work in different ways, if one does not control your seizures it doesn't mean that other ASMs won't work. If you change from one ASM to another, the second ASM is usually added and slowly increased to a dose which is likely to work, and the original drug is slowly reduced. 

If your seizures are not controlled with a single ASM you may take a combination of ASMs. This is called polytherapy. Some ASMs added to a first line ASM are called 'second line' ASMs. This is slightly different for children because ASMs are not split into first and second line for treating children age 12 and under. 

Some people continue to have seizures despite taking ASM. In this case they may continue to take ASM to reduce their seizures as much as possible and consider trying other types of treatment (see below).

What if medication doesn’t work for me?

Most people's seizures are controlled with medication. That is why medication is usually the type of treatment that is tried first. But if medication doesn't stop all your seizures, or only stops some of them, there are other types of treatment that might be considered. This might be instead of, or alongside ASM. Rather than waiting until you have tried lots of different ASMs, your specialist might talk to you about alternatives if two or three ASMs have not worked for you. 

If your seizures are not controlled with medication, your specialist may want to review your diagnosis to check that it is correct, to confirm the type of epilepsy or seizures you have, and to review the treatment you have had so far. They may refer you to a tertiary service (a specialist hospital or unit that focuses on specific care for different conditions) if they feel that more specialist treatment, other than ASM would be appropriate for you. 

For example, someone may be considered for epilepsy surgeryVNS (vagus nerve stimulation) therapy, or the ketogenic diet.

Information updated: August 2022

Sodium Valproate

Sodium valproate is an epilepsy drug prescribed for all seizure types including absence, myoclonus and tonic clonic seizures. It is also prescribed to a lesser degree for bipolar disorders. It is known under different brand names including Epilim, Epival, Episenta and Convulex.

New regulations have been introduced by the Medicines and Healthcare products Regulatory Agency (MHRA) around the way in which the drug, sodium valproate is prescribed to people, particularly women and girls, under the age of 55.


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