Last reviewed 2026-04-20 · How we verify

Zarontin (Ethosuximide)

Suppresses paroxysmal three cycle per second spike and wave activity associated with absence seizures.

Zarontin (ethosuximide) is a succinimide antiepileptic indicated for control of absence (petit mal) epilepsy. It works by suppressing spike and wave activity and elevating seizure threshold through motor cortex depression. Contraindicated in patients with succinimide hypersensitivity; requires monitoring of serum levels when used with other antiepileptic drugs due to potential interactions. Periodic serum level determinations recommended during concurrent antiepileptic therapy.

At a glance

Mechanism of action

Ethosuximide suppresses the paroxysmal three cycle per second spike and wave activity associated with lapses of consciousness which is common in absence (petit mal) seizures. The frequency of epileptiform attacks is reduced, apparently by depression of the motor cortex and elevation of the threshold of the central nervous system to convulsive stimuli.

Approved indications

• Absence seizure

Common side effects

• Gastrointestinal symptoms
• Nausea and vomiting
• Anorexia
• Gastric upset
• Abdominal pain
• Diarrhea
• Cramps
• Drowsiness
• Headache
• Dizziness
• Fatigue
• Lethargy

Serious adverse events

• Drug Reaction with Eosinophilia and Systemic Symptoms (DRESS)
• Stevens-Johnson syndrome
• Agranulocytosis
• Pancytopenia
• Bone marrow suppression
• Paranoid psychosis
• Suicidal intentions
• Leukopenia
• Thrombocytopenia
• Allergic reaction

Drug interactions

• Phenytoin
• Valproic acid

Primary sources

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