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.

About anti-seizure medication

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

ASM is a type of medication that aims to stop seizures from happening. It does not stop a seizure once it has started and it cannot cure epilepsy. 

Some medications are taken as a ‘course of treatment’ to cure a condition, for example, taking a course of antibiotics for an infection. 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 it 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 combined.

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. The specialist should have expertise in epilepsy. 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 (see below).

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. 

The National Institute for Health and Care Excellence (NICE) has recommendations about which ASMs should be used for different types of epilepsy and seizures. 

When an ASM is chosen, your specialist will take into account any other conditions you have, or medication you take. As you may be on ASM for a number of years, they will consider not just what is right for you 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, as some ASMs can affect an unborn baby (see below). 
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 (see below).

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. This is sometimes referred to as your ‘individual therapeutic concentration’. 

Therapeutic drug monitoring (TDM) uses blood levels to individualise epilepsy treatment to get the best seizure control with the least side effects. TDM can be very useful when starting medication, although not everyone is offered TDM.

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)

Epilepsy Society is grateful to Dr F J Rugg-Gunn, Consultant Neurologist & Honorary Associate Professor Clinical Lead, Chalfont Centre for Epilepsy, who reviewed this information.

Information updated: July 2024