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Generic Name:

ethosuximide, Oral capsule

All Brands

  • Zarontin
SECTION 1 of 5

Highlights for ethosuximide

Oral capsule
1

Ethosuximide is an oral drug that’s used to treat absence (petit mal) seizures in people with epilepsy.

2

The standard starting dose for adults is 500 mg taken by mouth once per day or 250 mg twice per day. Your total daily dose can be increased by 250 mg every 4–7 days until your seizures are controlled. 

3

Ethosuximide can cause serious side effects, including blood cell problems and liver or kidney damage. It can also cause severe skin reactions.

4

Drugs used to treat epilepsy can increase your risk of suicidal thoughts and actions. Call your doctor if you have any unusual changes in your mood or behavior, or if you have thoughts of hurting yourself.

IMPORTANT INFORMATION

Blood cells defects

Ethosuximide can cause abnormal amounts of your blood cells and platelets. This can be fatal.

Liver and kidney problems

This drug can harm your liver and kidneys. Use it with caution if you have liver or kidney disease.

Suicidal thoughts

Drugs used to treat epilepsy can increase your risk of suicidal thoughts and actions. Call your doctor if you have any unusual changes in your mood or behavior, or if you have thoughts of hurting yourself.

Multiorgan hypersensitivity

Ethosuximide can cause a severe allergic reaction. This is called Drug Reaction with Eosinophilia and Systemic Symptoms (DRESS). This reaction can occur at any time (as soon as 2–6 weeks after starting this drug) and may be fatal. Symptoms may include:

  • skin rash
  • fever
  • swollen lymph glands 
  • organ damage, including liver failure
  • yellowing of your skin or the whites of your eyes
  • swelling in the upper right quadrant of your stomach
  • change in urine output
  • trouble breathing
  • chest pain

What is ethosuximide?

Ethosuximide is a prescription drug. It’s available in these forms: oral capsule and oral solution.

Ethosuximide is available in its generic form. Generic drugs usually cost less. Talk to your healthcare provider to see if the generic will work for you.

Ethosuximide may be taken as part of a combination therapy with other anticonvulsants.

Why it's used

Ethosuximide is used to reduce or stop absence seizures (petit mal seizures) in people with epilepsy.

How it works

Ethosuximide belongs to a class of drugs called succinimide-type anticonvulsant agents or antiepileptic drugs (AEDs).

More Details

How it works

Ethosuximide belongs to a class of drugs called succinimide-type anticonvulsant agents or antiepileptic drugs (AEDs). A class of drugs refers to medications that work similarly. They have a similar chemical structure and are often used to treat similar conditions.

Ethosuximide works by reducing the number of seizures that cause you to lose consciousness. It prevents your brain from reacting to things that can cause you to have a seizure.

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SECTION 2 of 5

ethosuximide Side Effects

Oral capsule

Most Common Side Effects

The most common side effects that occur with ethosuximide include:

  • stomach problems, such as:

    • nausea
    • vomiting
    • diarrhea
    • stomach pain
    • indigestion
    • loss of appetite
  • weight loss

  • tiredness or fatigue

  • dizziness or lightheadedness

  • unsteadiness when walking

  • headache

  • trouble concentrating

  • hiccups

If these effects are mild, they may go away within a few days or a couple of weeks. If they’re more severe or don’t go away, talk to your doctor or pharmacist.

Serious Side Effects

If you experience any of these serious side effects, call your doctor right away. If your symptoms are potentially life threatening, or if you think you have a medical emergency, call 9-1-1.

  • serious allergic reactions, including Stevens-Johnson syndrome, which can be a life-threatening allergic skin reaction. Symptoms may include:

    • skin rash
    • hives
    • sores in your mouth, nose, or around your eyes
    • blistering or peeling skin
    • trouble breathing
    • swelling of your lips, tongue, or face
  • changes in thinking, mood, or behavior, such as:

    • suspicious thoughts
    • hallucinations (seeing or hearing things that aren’t there)
    • delusions (false thoughts or beliefs)
  • more frequent or worse grand mal seizures

  • life-threatening blood problems. Symptoms may include:

    • fever, swollen glands, or a sore throat that comes and goes, or doesn’t go away
    • frequent infections or an infection that doesn’t go away
    • bruising more easily than normal
    • red or purple spots on your body
    • bleeding from your gums or nosebleeds
    • severe fatigue or weakness
  • systemic lupus erythematosus, an autoimmune disease, while you’re taking the drug. Symptoms may include:

    • joint pain and swelling
    • muscle pain
    • fatigue
    • low-grade fever
    • pain in your chest that gets worse with breathing
    • unexplained skin rash
  • suicidal thoughts or actions. Symptoms may include:

    • thoughts about suicide or dying
    • attempts to commit suicide
    • new or worse depression or anxiety
    • panic attacks
    • trouble sleeping (insomnia)
    • new or worse irritability
    • acting aggressive or violent or being angry
    • acting on dangerous impulses
    • an extreme increase in activity and talking (mania)
Pharmacist's Advice
Clinical Associate Professor, University of Illinois at Chicago College of Pharmacy

Ethosuximide may cause drowsiness. Don’t operate a vehicle, use machinery, or do similar activities that require alertness until you know how this drug affects you.

Disclaimer: Our goal is to provide you with the most relevant and current information. However, because drugs affect each person differently, we cannot guarantee that this information includes all possible side effects. This information is not a substitute for medical advice. Always discuss possible side effects with a healthcare provider who knows your medical history.
SECTION 3 of 5

ethosuximide May Interact with Other Medications

Oral capsule

Ethosuximide can interact with other medications, herbs, or vitamins you might be taking. That’s why your doctor should manage all of your medications carefully. If you’re curious about how this drug might interact with something else you’re taking, talk to your doctor or pharmacist.

Note: You can reduce your chances of drug interactions by having all of your prescriptions filled at the same pharmacy. That way, a pharmacist can check for possible drug interactions.

Alcohol interaction

You shouldn’t drink alcohol while you’re taking ethosuximide. Combining this drug with alcohol can increase your chance of sleepiness or dizziness.

Medications that might interact with this drug

Phenytoin

Ethosuximide can cause the levels of this drug to increase in your body, which may put you at increased risk for side effects. Your doctor should check your blood levels regularly while you take these medications.

Valproic acid

This drug may increase or decrease the levels of ethosuximide in your body. Your doctor should check your blood levels regularly while you take these medications.

Disclaimer: Our goal is to provide you with the most relevant and current information. However, because drugs interact differently in each person, we cannot guarantee that this information includes all possible interactions. This information is not a substitute for medical advice. Always speak with your healthcare provider about possible interactions with all prescription drugs, vitamins, herbs and supplements, and over-the-counter drugs that you are taking.
Ethosuximide warnings
liver disease
People with liver disease

Ethosuximide can harm your liver. Use it with caution if you have liver disease.

kidney disease
People with kidney disease

Ethosuximide can harm your kidneys. Use it with caution if you have kidney disease.

grand mal seizures
People with grand mal seizures

Ethosuximide may increase the frequency of grand mal seizures in some people.

pregnant women
Pregnant women

Ethosuximide is a category C pregnancy drug. That means two things:

  1. Research in animals has shown adverse effects to the fetus when the mother takes the drug.
  2. There haven’t been enough studies done in humans to be certain how the drug might affect the fetus.

Talk to your doctor if you’re pregnant or planning to become pregnant. This drug should only be used if the potential benefit justifies the potential risk to the fetus.

Ethosuximide crosses the placenta, and may cause birth defects if you take it during pregnancy. However, drugs that treat seizures should generally not be stopped during pregnancy. If you stop the medicine and have a seizure, you and your baby could have serious complications. Talk to your doctor about the best way to manage your seizures during pregnancy.

If you become pregnant while taking ethosuximide, you should enroll in the North American Antiepileptic Drug (NAAED) Pregnancy Registry.  This group collects information about the safety of drugs that treat seizures during pregnancy. You can enroll by calling 1-888-233-2334.

breastfeeding
Women who are breast-feeding

Ethosuximide passes through breast milk. It may cause serious effects in a breastfeeding child.

Talk to your doctor is you’re currently taking ethosuximide and are considering breastfeeding.

for children
For children

Children may tolerate the liquid form of this drug better than the oral capsule. The safety and effectiveness of ethosuximide in people younger than 3 years haven’t been established.

call doctor
When to call the doctor

Call your doctor if the number of seizures you have increases or if you start having a different type of seizure.

allergies
Allergies

Ethosuximide can cause a severe allergic reaction called Stevens-Johnson syndrome, which may be fatal. Symptoms of an allergic reaction include:

  • rash
  • hives
  • peeling or blistering skin
  • sores in your mouth, nose, or around your eyes
  • trouble breathing
  • swelling of your tongue, lips, or face

Don’t take this drug again if you’ve ever had an allergic reaction to it or other succinimide anticonvulsants. Taking it again could be fatal.

SECTION 4 of 5

How to Take ethosuximide (Dosage)

Oral capsule

All possible dosages and forms may not be included here. Your dose, form, and how often you take it will depend on:

  • your age
  • the condition being treated
  • how severe your condition is
  • other medical conditions you have
  • how you react to the first dose

What are you taking this medication for?

Epileptic absence seizures

Brand: Zarontin

Form: Oral capsule
Strengths: 250 mg
Form: Oral solution
Strengths: 250 mg/5mL

Generic: ethosuximide

Form: Oral capsule
Strengths: 250 mg
Form: Oral solution
Strengths: 250 mg/5mL
Adult dosage (ages 18 years and older)
  • Starting dose: 500 mg taken by mouth once per day or 250 mg twice per day. Your doctor may increase your total daily dose by 250 mg every 4–7 days until your seizures are controlled. 
  • Maximum recommended dose: 1.5 g per day (taken in divided doses). If your doctor chooses to go higher than this, then you’ll need extra monitoring.
  • The usual maintenance dose is 20–40 mg/kg/day given in 2 divided doses.
Child dosage (ages 6-17 years)
  • Starting dose: 500 mg taken by mouth once per day. Your doctor may increase your total daily dose by 250 mg every 4–7 days until your seizures are controlled. The best dose for most children is 20 mg/kg per day.
  • Maximum recommended dose: 1.5 g per day (taken in divided doses). If your doctor chooses to go higher than this, then you’ll need extra monitoring.
Child dosage (ages 3-6 years)
  • Starting dose: 250 mg taken by mouth once per day. Your doctor may increase your total daily dose by 250 mg every 4–7 days until your seizures are controlled. The best dose for most children is 20 mg/kg per day.
  • Maximum recommended dose: 1.5 g per day (taken in divided doses). If your doctor chooses to go higher than this, then you’ll need extra monitoring.
Child dosage (ages 0-2 years)

The safety and effectiveness of ethosuximide in people younger than 3 years haven’t been established.

Special considerations

People with liver disease. Ethosuximide should be used with great caution if you have liver disease. Your doctor will periodically monitor your liver function.

People with kidney disease: Ethosuximide should be used with great caution if you have kidney disease. Your doctor will periodically monitor your kidney function.

Warnings

Your total daily dose should be increased in small increments (250 mg) every 4–7 days until your seizures are under control.

Disclaimer: Our goal is to provide you with the most relevant and current information. However, because drugs affect each person differently, we cannot guarantee that this list includes all possible dosages. This information is not a substitute for medical advice. Always to speak with your doctor or pharmacist about dosages that are right for you.
Pharmacist's Advice
Clinical Associate Professor, University of Illinois at Chicago College of Pharmacy

Ethosuximide comes with serious risks if you don’t take it as prescribed.

If you don’t take it at all

Your seizure condition won’t improve and may get worse.

If you don’t take it on schedule

The drug may not be as effective. Stopping an anti-seizure medicine suddenly can cause seizures that won’t stop. This condition can be fatal. Don’t stop taking this medicine without talking to your doctor first.

If you take too much

Taking too much ethosuximide can cause severe side effects, such as nausea, vomiting, shallow or slowed breathing, drowsiness, and coma. Call your doctor right away or go to the emergency room if you think that you’ve taken too much.

What to do if you miss a dose

If you miss a dose, take it as soon as possible. If it’s almost time for your next dose, skip the missed dose and go back to your normal schedule.

Don’t take two doses at the same time to make up for the missed dose. This could result in toxic side effects.

How to tell if the drug is working

You may be able to tell this medicine is working if your seizures are better controlled.

Ethosuximide is a long-term drug treatment used to manage seizure disorder.

Important considerations for taking ethosuximide
timing
Take ethosuximide at the same time each day
do not crush or cut
Don’t crush or cut the capsule
storage
Store at room temperature from 68–77°F (20–25°C)
See Details
prescription is refillable
Prescription is refillable
travel
Travel
See Details
clinical monitoring
Clinical monitoring
See Details
prior authorization
Insurance
See Details

Store at room temperature from 68–77°F (20–25°C)

Don’t freeze ethosuximide.

Keep it in the original container.

Keep this drug away from light and high temperature.

Keep your drugs away from areas where they could get wet, such as bathrooms. Store this drug away from moisture and damp locations.

Travel

When traveling with your medication:

  • Always carry your medication with you or in your carry-on bag.
  • Don’t worry about airport X-ray machines. They can’t hurt this medication.
  • You may need to show your pharmacy’s label to clearly identify the medication. Keep the original prescription label with you when traveling.
  • Make sure that you have enough ethosuximide before you travel. You don’t want to run out of this medication when you’re traveling.

Clinical monitoring

Before starting and during treatment with ethosuximide, your doctor may do tests to check your:

  • liver function
  • kidney function
  • blood counts
  • blood concentrations of ethosuximide

Insurance

Many insurance companies will require a prior authorization before they approve and pay for the brand name product Zarontin. The generic ethosuximide usually doesn’t require a prior authorization.

Are there any alternatives?

There are other drugs available to treat your condition. Some may be more suitable for you than others. Talk to your doctor about possible alternatives.

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How Much Does ethosuximide Cost?

Oral capsule

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Lowest price for ethosuximide

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These prices represent the lowest priced national pharmacies for ethosuximide on GoodRx. They may be lower than your insurance.

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Content developed in collaboration with University of Illinois-Chicago, Drug Information Group

Medically reviewed by Creighton University, Center for Drug Information and Evidence-Based Practice on August 4, 2015

Disclaimer: Healthline has made every effort to make certain that all information is factually correct, comprehensive, and up-to-date. However, this article should not be used as a substitute for the knowledge and expertise of a licensed healthcare professional. You should always consult your doctor or other healthcare professional before taking any medication. The drug information contained herein is subject to change and is not intended to cover all possible uses, directions, precautions, warnings, drug interactions, allergic reactions, or adverse effects. The absence of warnings or other information for a given drug does not indicate that the drug or drug combination is safe, effective, or appropriate for all patients or all specific uses.
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