Category 1 – phenytoin, carbamazepine, phenobarbital, primidone
For these drugs, doctors are advised to ensure that their patient is maintained on a specific manufacturer’s product

Category 2 – valproate, lamotrigine, perampanel, retigabine, rufinamide, clobazam, clonazepam, oxcarbazepine, eslicarbazepine, zonisamide, topiramate
For these drugs, the need for continued supply of a particular manufacturer’s product should be based on clinical judgement and consultation with patient and/or carer, taking into account factors such as seizure frequency and treatment history

Category 3 - levetiracetam, lacosamide, tiagabine, gabapentin, pregabalin, ethosuximide, vigabatrin 
For these drugs, it is usually unnecessary to ensure that patients are maintained on a specific manufacturer’s product unless there are specific reasons such as patient anxiety and risk of confusion or dosing error

How to ensure you are prescribed the same AEDs

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Ask your doctor to prescribe you the  brand name so the pharmacist will  give you that AED

If your doctor writes the generic name of the AED on your prescription, ask if it can include  the name of the specific drug company.

Try to use  the same pharmacist each time as they may have a record of your AEDs and may ensure that you receive the same AED

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How long does it take for seizure medicines to reach the bloodstream?

A dose of medication will reach a peak, or maximum, level in the blood 30 minutes to 4 or 6 hours after it is taken.
The peak time varies for different drugs.
The time between taking the medication and reaching the peak level depends on the specific medicine and what form it is in, for example a liquid, tablets, capsule or slow-release form.
In general, liquids are absorbed quickly.
Medications in slow-release forms are absorbed gradually over hours and produce the steadiest levels in the blood. These slow-release forms can be taken less often, once or twice a day.
Eating before a dose may also affect how long it takes to reach a peak level.
I have heard the term "half-life" used to talk about medications.

What does this mean?
A medicine's half-life is the time it takes for its level in the blood to be reduced by one-half.
The half-life of each seizure medicine depends on how quickly it is broken down and gotten rid of from the body.
How often a medicine should be taken depends on the drug’s half-life.

What's the difference between a medicine that has a short half-life and one with a long half-life?
If a medicine has a short half-life, the amount in your blood may quickly become too low to control your seizures. Medicines with short half-lives ideally should be taken several times a day.
Then you can take a smaller amount each time and your blood level will stay more stable.
Medicines with long half-lives have more stable levels over a number of hours. This let’s the medicine be taken less often.

When are seizure medicines most likely to work?
Seizure medicines work best when the amount in your system reaches a steady state or constant amount.
To keep this steady or constant amount, the medicine needs to be taken on a regular basis. The amount you take in needs to equal the amount your body gets rid of.
Just because a medicine has reached a steady state doesn’t mean that it will control seizures. Only by taking the medicine for a while (usually a number of months) can you tell if the drug is going to work for you

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Is it normal for blood levels of seizure medicines to fluctuate?
Yes, even when someone has been taking the same medication for a long time the amount in your body will change over the course of the day.
Missed doses can also be a reason for why medicine levels change.
Dose-related side effects are more likely to occur at times of the highest (peak) levels and a seizure is more likely to occur at times of the lowest (trough) levels

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Experts suggest the following for avoiding drug interactions with epilepsy drugs.

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• Be honest. Tell your doctor, dentist, and pharmacist about all the medicines, supplements, vitamins, and herbs you use. Go into appointments with a list so you don't forget anything.

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• Don't assume that "natural" means safe. Many herbal medicines and supplements can interact with medicines for epilepsy. "For instance,

• St. John's wort can interact with several anticonvulsant medicines," says Pellock.

• What is the best home remedy for seizures?

• Some herbs, such as chamomile, passionflower, and valerian, may make AEDs more effective and calming. However, ginkgo, ginseng, and stimulating herbs containing caffeine and ephedrine can make seizures worse

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• Be careful with birth control pills. Some medicines for seizures can prevent birth control pills from working. Epilepsy drugs known to have this effect include Carbatrol, Dilantin, phenobarbital, Mysoline, Trileptal, and Topamax.

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• Take special precautions if you're older. Older people are not only more likely to have epilepsy than other adults, but they're also more likely to be on long-term medication for other conditions like high blood pressure, diabetes, or heart problems. That increases your risk of interactions.

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• Watch your diet. Oddly enough, some foods -- like grapefruit -- can interact with epilepsy medicines. Ask your doctor for a list of any foods you should avoid.

  More generally, you should not make radical changes to your eating habits. "Some of these popular diets can cause havoc in people with epilepsy," says Pellock. "That's not just from the weight loss, but from the extreme diet changes they make to achieve it."

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• What foods should you avoid if you have epilepsy?

• Foods which may cause energy peaks and slumps include:

• white bread; non-wholegrain cereals; biscuits and cakes; honey; high-sugar drinks and foods; fruit juices; chips; mashed potatoes; parsnips; dates and watermelon. In general, processed or overcooked foods and over-ripe fruits

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• Keep your doctor up to date. If you need to start taking medicines for another condition -- or have to change any of your doses -- talk to your doctor before you start.

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Updated April 2024