Ethosuximide for Treating Seizures

Medication for absence seizures

10 year old boy looking into the distance, day dreaming maybe
Ian Ross Pettigrew/Moment/Getty Images 

Ethosuximide (trademarked Zarontin) is a prescription anti-epileptic medication primarily used to treat a specific type of seizure known as an “absence seizure.”

Like all anti-epileptic 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 your experience and behavior. These vary depending on the part of the brain that's 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 can frequently miss portions of lessons. Untreated absence seizures can also pose a safety challenge, and untreated children will need to avoid certain activities until their disease is under control.


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 anti-epileptic 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’s active ingredient is a chemical called alpha-ethyl-alpha-methylsuccinimide. It is not exactly clear how this drug works. Like other ​anti-epileptic drugs, though, 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, which is 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.

In a 2017 review of studies on ethosuximide, researchers concluded that this medication is the best first-line single treatment (monotherapy) for children and adolescents with absence seizures.

They add, though, that in someone who also has generalized tonic-clonic seizures, valproate is a more appropriate treatment.


Ethosuximide is available in both capsule and liquid preparations. It's generally started at a low dose and increase gradually under the supervision of a doctor. The goal is to reach a dose that will control seizures with minimal side effects.

The 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 people 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.

To minimize your risk of seizures, take ethosuximide exactly as prescribed. If you accidentally miss a dose, go ahead and take it as soon as you remember. However, if it is already time for another dose, don’t double up. 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 suddenly, as that can cause seizures. If you're having a problem with this drug, contact your doctor. Lowering your dosage may help with side effects. If weaning off of ethosuximide is the right choice for you, your doctor will give you instructions for slowly reducing your dosage until it's safe to stop taking it.

Side Effects

Like all medications, ethosuximide comes with potential side effects. The most common ones include:

  • Abdominal discomfort
  • Nausea
  • Drowsiness
  • Headache
  • Dizziness
  • Rash
  • Problems with the liver or kidneys (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.

In children, studies show ethosuximide can cause attentional dysfunction, psychomotor slowness, and a drop in alertness. Researchers stated that these effects were mild and comparable to those of other anti-epileptic drugs.

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, contact your doctor.

Due to the potential for problems with blood cells, the liver, and the kidneys, you may need periodic blood and urine tests while taking this medication.

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 anti-epileptic drugs.

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 they can increase the risk of depression as well. You and your health care provider can weigh the risks and benefits of medication for your particular situation.


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. If you are taking ethosuximide and find out you are pregnant, don’t immediately stop taking it. Instead, call your doctor’s office. If you need to go off the drug, your doctor can help get you to do so 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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