Ethosuximide: A Complete Overview

Ethosuximide is a prescription anticonvulsant medication used to treat absence seizures (petit mal seizures) in patients aged 3 and older. It belongs to the succinimide class of drugs and is one of the most effective and commonly prescribed treatments for this type of epilepsy.

What Is Ethosuximide?

Ethosuximide is the generic name for the brand-name drug Zarontin, manufactured by Pfizer. It was first approved by the FDA in the 1960s and has been a cornerstone of absence seizure treatment ever since.

Here are the key facts:

• Drug class: Succinimide anticonvulsant
• Brand name: Zarontin
• Manufacturer: Pfizer (brand); multiple generic manufacturers
• Generic available: Yes
• Controlled substance: No — Ethosuximide is not a DEA-scheduled controlled substance
• Available forms: 250 mg capsules, 250 mg/5 mL oral solution (syrup)

Ethosuximide works by blocking T-type calcium channels in the thalamocortical neurons of the brain. This reduces the abnormal electrical discharges that cause absence seizures.

What Is Ethosuximide Used For?

Ethosuximide is FDA-approved for one primary use:

• Absence seizures (petit mal seizures) in patients aged 3 and older

Absence seizures are brief episodes—usually lasting 5 to 30 seconds—where a person suddenly "blanks out" or stares into space. They're most common in children between ages 4 and 14. Unlike other types of seizures, absence seizures don't cause convulsions or falling.

Ethosuximide is considered a first-line treatment for absence seizures. In clinical studies, it has been shown to be as effective as Valproic Acid (Depakote) and more effective than Lamotrigine (Lamictal) for controlling absence seizures, with fewer side effects than Valproic Acid.

Some off-label uses include neuropathic pain and certain other epilepsy syndromes like Jeavons syndrome (epilepsy with eyelid myoclonia), though these uses are less common.

How Is Ethosuximide Taken?

Ethosuximide is taken by mouth, either as capsules or liquid syrup. Here's what you need to know about dosing:

Adults (age 7 and older)

• Starting dose: 500 mg once daily
• Dose adjustments: Increase by 250 mg every 4 to 7 days as needed
• Typical maintenance dose: 500 mg to 1,500 mg daily
• Maximum dose: 1,500 mg per day

Children (ages 3 to 6)

• Starting dose: 250 mg daily (or 125 mg twice daily)
• Dose adjustments: Increase gradually based on response
• Maximum dose: 20 mg/kg per day

Important dosing tips

• Can be taken with or without food. Taking it with food helps reduce nausea.
• The liquid form is helpful for young children or anyone who has trouble swallowing capsules.
• Can be taken once daily or split into two doses.
• Never stop Ethosuximide suddenly. Abrupt discontinuation can cause absence status epilepticus—a prolonged seizure. Always taper gradually under your doctor's supervision.

Who Should Not Take Ethosuximide?

Ethosuximide is not right for everyone. You should not take it if you have:

• A known allergy to Ethosuximide or other succinimide medications
• A history of Ethosuximide-induced immune thrombocytopenia (a rare blood disorder)

Use with caution if you have:

• Liver disease or impairment
• Kidney disease (dose adjustment may be needed if CrCl is below 30 mL/min)
• A history of depression or mental health conditions (due to the FDA class warning about suicidal thoughts with all antiseizure medications)

If you're pregnant or breastfeeding, talk to your doctor before taking Ethosuximide. It's classified as Pregnancy Category C and does cross the placenta. It's also excreted in breast milk. For more on side effects and precautions, see: Ethosuximide Side Effects.

How Much Does Ethosuximide Cost?

The cost of Ethosuximide varies significantly depending on whether you have insurance, use coupon cards, or pay cash:

• Cash price (no insurance): $200 to $580 for a 30-day supply
• With coupon cards: As low as $32 (GoodRx) to $36 (SingleCare) for generic Ethosuximide
• With insurance: Generic Ethosuximide is covered by most Medicare and commercial insurance plans as a preferred generic. Copays are typically low.

Brand-name Zarontin is significantly more expensive and may require prior authorization. In most cases, the generic version is equally effective and much more affordable.

For a complete breakdown of savings options, coupons, and patient assistance programs, see: How to Save Money on Ethosuximide.

Final Thoughts

Ethosuximide has been a trusted treatment for absence seizures for over 60 years. It's effective, well-studied, and available as an affordable generic. If you or your child has been prescribed Ethosuximide, understanding how it works, how to take it, and what to watch for can help you get the most out of your treatment.

Having trouble finding Ethosuximide at your pharmacy? It's a niche medication that not every store keeps in stock. Medfinder can help you locate pharmacies near you that have it available. You can also read our guide on how to check pharmacy stock without calling.