Key Facts About Ethosuximide for Seizures

One Helpful Treatment for Absence Seizures

10 year old boy looking into the distance, day dreaming maybe
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Ethosuximide (trademarked Zarontin) is an antiepileptic medication primarily used to treat a specific type of seizure known as an “absence seizure.” Like all antiepileptic medications, it carries a risk of increasing suicidal thoughts in certain people. However, it is generally a safe and effective medicine.

Absence Seizures

In general, seizures are characterized by abnormal patterns of neurons firing in the brain.

This abnormal firing causes temporary changes in a person’s experience and behavior. These vary depending on the part of the brain affected. Some people with seizures have other medical problems that are affecting the brain, either permanently or temporarily. Other people with seizures have a condition called epilepsy, which causes a person to experience chronic seizures.

Absence seizures are a type of seizure that changes the electrical activity of the brain in a particular way and in a particular location. They are sometimes called “petit mal” seizures. These seizures cause reduced consciousness for a brief period (often just a few seconds), during which a person has reduced awareness of their environment.

When someone is having an absence seizure they might appear to be staring out into space, and they might display automatic movements, like tapping their fingers. The symptoms are often more subtle than some other types of seizures.

Absence seizures are more common in children than adults.

It is important to get treatment for absence seizures. Absence seizures can reduce a child's academic performance, because they are missing part of what is shared in class. Untreated absence seizures can also pose a safety challenge, and untreated children will need to avoid certain activities until their disease is under control.

How Ethosuximide Works

Ethosuximide’s active ingredient is a chemical called alpha-ethyl-alpha-methylsuccinimide . It is not exactly clear how this drug works. However, like other ​antiepileptic drugs, it helps suppress abnormal electrical activity in the brain.

Specifically, ethosuximide may work through its effect on a specific type of calcium channel in the brain. This channel affects the brains excitability, how often certain neurons send electrical signals.

Ethosuximide may change how often the channel opens and closes. This helps stabilize the brain’s electrical activity and thus helps prevent absence seizures in particular.


Ethosuximide is FDA approved for people with absence seizures, and it has been used for this for many years. It is one of the most common drugs approved for this condition. Lamotrigine and valproate are two other antiepileptic drugs commonly given for this type of seizure. Less commonly, ethosuximide is given to people with other seizure types, usually in addition to other drugs.


Ethosuximide is available in both capsule and liquid preparations. People needing ethosuximide usually begin with a starting dose and increase gradually under the supervision of a physician.

The goal is to get a dose that will control seizures with minimum side effects. Final dosing will vary based on the patient’s weight and other factors. Ethosuximide should be stored at room temperature away from light. It can be taken with or without food.

Some patients need to take ethosuximide in combination with other anticonvulsant drugs (such as valproate) to control their seizures. Make sure to tell your doctor about all the medicines that you take,
including over-the-counter medicines, since these can affect how well the drug works.

It is important to take ethosuximide exactly as prescribed, to minimize your risk of seizures.

If you accidentally skip a dose, go ahead and take the dose as soon as you remember. However, if it is already time for another dose, don’t double up your doses. Just take your regular amount.

If you accidentally take more ethosuximide than you should, contact your doctor immediately, or go to your emergency care center. A major overdose of ethosuximide might cause serious problems like reduced breathing. If this occurs, health professionals will need to intervene to decrease the amount of drug in your body.

Don’t stop taking ethosuximide without talking to your doctor about it first. If you do, you may have a seizure. If you are having a problem with ethosuximide, contact your health provider. Your doctor will help you get off the drug safely, if that is right for you. Your doctor can help reduce your dose slowly, to minimize the risk of seizures.

Suicidal Thoughts

It’s important to be aware of one uncommon but very important potential side effect of ethosuximide: suicidal thoughts. This is a dangerous potential side effect of all antiepileptic drugs, including ethosuximide.

It is important to watch out for any worsening signs or symptoms of depression or other unusual changes in a person's mental state or behavior. If these emerge, it is important to seek professional help right away. Of course, not all people taking ethosuximide will experience this side effect.

Though it is important to be aware of this potential problem, untreated seizures also carry their own risks, and can increase the risk of depression as well. You and your health care provider can weigh the risks and benefits in your particular situation.

Potential Side Effects

Like all medications, ethosuximide comes with potential side effects. Some of the most common are gastric complaints, like abdominal discomfort or nausea. Some other potential side effects are as follows:

  • Drowsiness
  • Headache
  • Dizziness
  • Rash
  • Problems with the liver or kidney (rare)

Because of the drowsiness that ethosuximide can cause, it is important to be cautious about driving and other potentially dangerous tasks. This is especially important if one is just getting used to the medication.

Rarely, ethosuximide can also cause a serious problem in which a person’s blood cells aren’t working well. This might show up as signs of an infection (like sore throat and fever) or as symptoms of easy bruising or very pale appearance. If these occur soon after taking ethosuximide, consult with your physician.

Because of the risk of certain side effects from ethosuximide, people taking the drug may need periodic blood and urine tests. These tests can make sure that your liver, kidney, and blood cells are all still functioning well.


People who are known to be allergic to other medicines in the succinimide family should not take ethosuximide.

Caution should also be used in pregnant and breastfeeding women. Ethosuximide may increase the risk of birth defects. However, if you are taking ethosuximide and find out you are pregnant, don’t immediately stop taking it. Instead, call your doctor’s office. If desirable, your doctor can help get you off the drug safely.

A Word From Verywell

Ethosuximide can be a helpful drug for many people with absence seizures. As with all drugs, it comes with potential side effects. Talk to your health provider to see if ethosuximide makes sense in your situation.

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Article Sources
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  • Zarontin [package insert]. NY, NY: Pfizer. 2009.
  • Zarontin [package leaflet]. Tadworth, England: Pfizer Limited. 2015.