Zarontin (Ethosuximide) for Treating Seizures

This medication is mainly for absence seizures

Table of Contents
View All
Table of Contents

Zarontin (ethosuximide) is a prescription anti-epileptic medication primarily used to treat a specific type of seizure known as an absence seizure. The drug is suspected to work by decreasing the abnormal electrical activity in the brain that gives way to these seizures, which reduces consciousness for a brief period of time. Zarontin is generally considered a safe and effective medicine. But like all anti-epileptic medications, it carries a risk of increasing suicidal thoughts in certain people.

Baby boy drinking medicine off a spoon. Debica, Poland
Anna Bizon / Getty Images

Absence seizures are more common in children than adults. It is important to get treatment early on, and Zarontin is considered the best option to try first. These seizures can reduce a child's academic performance and pose safety challenges, and children with absence seizures will need to avoid certain activities until their condition is under control.


Zarontin is approved by the U.S. Food and Drug Administration (FDA) for people with absence seizures, and it has been used for this for many years. It is one of the most common drugs prescribed for this condition. Lamotrigine and valproate are two other anti-epileptic drugs commonly given for this type of seizure.

In fact, 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.

Less commonly, Zarontin is given to people with other seizure types, usually in addition to other drugs.

How It Works

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 by changing how often a specific type of calcium channel in the brain opens and closes. This affects the brains excitability (how often certain neurons send signals), which helps stabilize the brain’s electrical activity and, thus, help prevent absence seizures in particular.


Zarontin is available in both capsule and liquid preparations. It's generally started at a low dose that's increased gradually under the supervision of a healthcare provider. The goal is to reach a dose that will control seizures with minimal side effects. The final dosing will vary based on a 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 Zarontin in combination with other anticonvulsant drugs (such as valproate) to control their seizures. Make sure to tell your healthcare provider about all the medicines that you take, including over-the-counter medicines, since these can affect how well ethosuximide 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.

Overdose Warning

If you accidentally take more Zarontin than you should, contact your healthcare provider 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.

Stopping Zarontin

Stopping ethosuximide suddenly can cause seizures. If you're having a problem with this drug, contact your healthcare provider. Lowering your dosage may help with side effects, and your healthcare provider can give you instructions on how to slowly reduce your dosage until it's safe to stop taking the medication.

Side Effects

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

  • Abdominal discomfort
  • Nausea
  • Drowsiness
  • Headache
  • Dizziness
  • Rash

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, Zarontin 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 healthcare provider.

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

Suicidal Thoughts

It’s important to be aware of one uncommon but very significant potential side effect of ethosuximide (and all anti-epileptic drugs): suicidal thoughts.

Watch out for any worsening signs or symptoms of depression or other unusual changes in a person's mental state or behavior. If it's you taking the drug, try your best to acknowledge any of your own. If these emerge, seek professional help right away. Of course, not all people taking ethosuximide will experience this side effect.

While this is obviously a concern, untreated seizures also carry their own risks and can increase the risk of depression themselves. A healthcare provider can help weigh the risks and benefits of medication for a particular individual.


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

Ethosuximide may increase the risk of birth defects, so you should notify your healthcare provider if you find out you're pregnant. Await instruction instead of immediately stopping the drug.

Zarontin is not recommended while breastfeeding due to concerns about abnormalities in weight and developmental milestones.

Was this page helpful?
5 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Brigo F, Igwe SC. Ethosuximide, sodium valproate or lamotrigine for absence seizures in children and adolescents. Cochrane Database Syst Rev. 2017;2:CD003032. doi:10.1002/14651858.CD003032.pub3

  2. Posner E. Absence seizures in children. BMJ Clinical Evidence. 2013;2013:0317.

  3. IJff DM, van Veenendaal TM, Debeij-van Hall MH, et al. The cognitive profile of ethosuximide in children. Paediatr Drugs. 2016;18(5):379-85. doi:10.1007/s40272-016-0187-z

  4. Mula M, Hesdorffer DC. Suicidal behavior and antiepileptic drugs in epilepsy: analysis of the emerging evidenceDrug Healthc Patient Saf. 2011;3:15–20. doi:10.2147/DHPS.S13070

  5. Davanzo R, Dal Bo S, Bua J, et al. Antiepileptic drugs and breastfeeding. Ital J Pediatr. 2013 Aug 28;39:50. doi:10.1186/1824-7288-39-50

Additional Reading