Ethosuximide

Introduction

Written by Patricia Weiser, PharmD
Medically reviewed by Dena Westphalen, PharmD
Updated on September 27, 2023

Ethosuximide (eth oh SUKS i mide) is a generic medication prescribed for certain types of seizures due to epilepsy. Ethosuximide belongs to a group of drugs called anticonvulsants.

The Food and Drug Administration (FDA) has specifically approved ethosuximide to treat absence seizures (previously known as petit mal seizures).

Side effects of ethosuximide

Ethosuximide may cause mild or serious side effects. More common mild side effects of ethosuximide and its serious side effects are listed below. This article doesn’t include all possible side effects of the drug. Side effects can vary based on your age, overall health, and any other medications you take.

To learn more about ethosuximide’s side effects, ask your doctor or pharmacist. You can also refer to the prescribing information for ethosuximide listed in the “Resources” section.

Mild side effects

More common mild side effects of ethosuximide are listed below.

This article doesn’t include all possible mild side effects of the drug. To learn more about ethosuximide’s side effects, refer to the prescribing information for ethosuximide listed in the “Resources” section.

With many drugs, mild side effects may go away within a few days or a couple of weeks. If the side effects are bothersome, tell your doctor or pharmacist. They may be able to suggest ways to manage them.

Ethosuximide oral capsule’s and ethosuximide oral solution’s mild side effects include:

• digestive side effects, such as nausea, vomiting, indigestion, abdominal pain, diarrhea, or decreased appetite
• weight loss
• hiccups
• fatigue (low energy)
• mild allergic reaction*

* For details about this side effect, see the “Interactions and warnings for ethosuximide” section.

Serious side effects

Serious side effects of ethosuximide are listed below.

This article doesn’t include all possible serious side effects of the drug. To learn more about ethosuximide’s side effects, refer to the prescribing information for ethosuximide listed in the “Resources” section.

With many drugs, serious side effects are possible but not common. If you have serious side effects from this drug, call your doctor right away. If you’re having severe symptoms or a medical emergency, call 911 or a local emergency number.

In general, ethosuximide’s serious side effects include:

• liver problems
• kidney problems
• drug-induced immune thrombocytopenia, a condition that lowers the number of platelets in your body, which can increase the risk of bleeding problems
• blood disorders, such as low levels of white blood cells, which can increase the risk of infection
• systemic lupus erythematosus or “lupus” (an autoimmune disease) while you’re taking the drug
• serious skin reactions that cause your skin to blister and peel, including drug reaction with eosinophilia and systemic symptoms (DRESS), which can cause your organs to quit working correctly
• changes in mood or behavior, such as suicidal thoughts or actions, or aggressiveness
• severe allergic reaction*

* For details about this side effect, see the “Interactions and warnings for ethosuximide” section.

Suicide prevention

If you or someone you know is in crisis and considering suicide or self-harm, please seek support:

• Call the 988 Suicide and Crisis Lifeline at 988.
• Text HOME to the Crisis Textline at 741741.
• Not in the United States? Find a helpline in your country with Befrienders Worldwide.
• Call 911 or your local emergency services number if you feel safe to do so.

If you’re calling on behalf of someone else, stay with them until help arrives. You may remove weapons or substances that can cause harm if you can do so safely.

If you are not in the same household, stay on the phone with them until help arrives.

Common questions about ethosuximide

Below you’ll find answers to a few commonly asked questions about ethosuximide.

What brand names are available for ethosuximide?

Both the oral capsule and oral solution (syrup) forms of ethosuximide are available under the brand-name Zarontin.

Ethosuximide is a generic drug. A generic medication is an identical copy of the active drug in a brand-name medication. (An active drug is the ingredient that makes a medication work.) Generic drugs are believed to be as effective and safe as brand-name drugs. And generic drugs typically cost less compared to brand-name drugs.

If you’d like to know more about this, talk with your doctor or pharmacist.

How does ethosuximide work? And how long does it take to start working?

The exact way ethosuximide works (its mechanism of action) isn’t fully known.

With absence seizures, a specific wave-like pattern of electrical signaling occurs in the brain. This pattern is linked to a brief loss of consciousness. Ethosuximide is believed to manage this brain pattern, which helps prevent absence seizures in certain people with epilepsy (seizure disorders).

Ethosuximide starts working soon after your first dose. But it may take several weeks before you notice fewer seizures. This is because your doctor will likely start you with a low dose of ethosuximide. They’ll slowly increase your dosage over 2–4 weeks until they find the amount that’s effective for you.

Talk with your doctor or pharmacist if you’d like to know more about what to expect with ethosuximide.

Does ethosuximide cause long-term side effects?

No, long-term side effects aren’t expected with ethosuximide. In studies, specific side effects weren’t seen in people who had taken the drug for a long time. Long lasting side effects after treatment ended also weren’t reported.

Talk with your doctor if you have questions about possible long-term side effects with ethosuximide.

Uses of ethosuximide

The Food and Drug Administration (FDA) approves prescription drugs such as ethosuximide for certain conditions. Approved uses for ethosuximide are described below.

Use for certain seizures

Doctors may prescribe ethosuximide oral capsule or ethosuximide oral solution for managing absence seizures (previously known as petit mal seizures). It’s used for this purpose in children ages 3 years and older and adults who have epilepsy. It’s usually prescribed as a long-term treatment.

With absence seizures, brief changes in electrical activity occur in the brain. This leads to symptoms that are sometimes barely noticeable, such as:

• briefly staring into space
• appearing to “freeze” or suddenly become motionless
• interruptions in speech
• fluttering eyelids

If someone has other types of seizures besides absence seizures, their doctor may prescribe ethosuximide along with other anticonvulsant drugs, such as carbamazepine (Carbatrol, Tegretol, others).

Interactions and warnings for ethosuximide

Below you’ll find information about ethosuximide’s possible interactions and warnings.

Interactions of ethosuximide

Certain things may affect how a drug works. These include getting vaccines, consuming alcohol or certain foods, or taking the drug with other medications. This effect is called a drug interaction.

Before you take ethosuximide, ask your doctor to check for possible interactions. Be sure to tell them about any of the following you take or use:

• prescription or over-the-counter drugs
• vitamins, herbs, or supplements

To learn about drug-condition interactions, see the “Warnings for ethosuximide” section below.

Warnings for ethosuximide

Some people should not take ethosuximide, and others should take it cautiously.

Ethosuximide could cause harm to people with certain health conditions. This effect is called a drug-condition interaction. Other factors can also affect whether ethosuximide is a safe option for you.

Ask your doctor about specific warnings for ethosuximide, and be sure to tell your doctor about your:

• current health, including any allergies to medications
• past health conditions or surgeries

Allergic reaction

Ethosuximide can cause an allergic reaction in some people. Severe allergic reactions are rare but possible.

If you’ve had an allergic reaction to ethosuximide or any of its ingredients, your doctor will likely not prescribe ethosuximide. They can tell you about medications that are safer options for you.

A mild allergic reaction may cause the following symptoms:

• skin rash
• itchiness
• flushing (temporary warmth, redness, or deepening of skin color)

A severe allergic reaction may cause the following symptoms:

• severe skin rashes that may blister and peel
• swelling under your skin, usually in your hands, feet, eyelids, or lips
• swelling of your mouth, throat, or tongue, which can cause breathing problems

If you have an allergic reaction to ethosuximide, call your doctor right away. If you have severe symptoms, call 911 or a local emergency number.

Overdose of ethosuximide

You should not take more ethosuximide than your doctor prescribes. For some drugs, doing so may lead to harmful effects or overdose.

If you think you’ve taken too much ethosuximide, call your doctor or pharmacist right away. Or you could call 800-222-1222 to speak with someone at America’s Poison Centers. You can also use its online resource. If you have concerning symptoms, call 911 or a local emergency number immediately. You can also go to the closest emergency room.

Pregnancy or breastfeeding and ethosuximide

Information about ethosuximide and pregnancy and breastfeeding is described below.

Ethosuximide and pregnancy

There are risks to taking ethosuximide during pregnancy. But there are also risks with having an untreated seizure disorder while pregnant. (Keep in mind that ethosuximide is used for managing certain seizures due to epilepsy.)

If you’re planning a pregnancy or can become pregnant, talk with your doctor about seizure treatment options during pregnancy. Together, you can discuss the risks and benefits of your treatment options and decide whether or not you should take ethosuximide during pregnancy.

If you take ethosuximide at any point during pregnancy, your doctor may encourage you to join a pregnancy registry. It collects information about the safety of medications during pregnancy. For more details, contact the North American Antiepileptic Drug Pregnancy Registry at 888-233-2334 or visit the website.

Ethosuximide and breastfeeding

It isn’t known whether ethosuximide is safe to take while breastfeeding.

If you plan to breastfeed, talk with your doctor about epilepsy treatment options. Together, you can discuss the possible risks and benefits of your treatment options and decide whether or not you should take ethosuximide during this time. Your doctor may recommend other healthy ways to feed your child.

What to ask your doctor

Let your doctor know if you have questions about ethosuximide or would like more details about it.

Here’s a list of some possible questions you may want to ask your doctor:

• Considering my other medications, when should I take ethosuximide?
• What are my options if I can’t afford ethosuximide?
• How does ethosuximide compare to any alternative medications used to treat my condition?

Resources

• Ethosuximide capsules, USP. (2022). https://nctr-crs.fda.gov/fdalabel/services/spl/set-ids/a4dbc665-4db1-4d0a-9630-5cd200ec4c82/spl-doc
• Ethosuximide oral solution. (2022). https://nctr-crs.fda.gov/fdalabel/services/spl/set-ids/19c924c2-f558-4c78-9277-2d7e0df2f505/spl-doc
• Food and Drug Administration. (2023). Orange Book: Approved drug products with therapeutic equivalence evaluations. https://www.accessdata.fda.gov/scripts/cder/ob/index.cfm

Disclaimer: Optum Perks 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 another 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.