Ethosuximide
ZARONTIN
Pronunciation: eth-oe-SUX-i-mide
“Zorro’s Ethics suck!”
Child with petit mal seizure (approved for age 3+)
Drug of choice for absence seizures
What it isT-type calcium-channel blocker in thalamic neurons; absence seizures.
Why this oneFirst-line for childhood absence epilepsy and preserves attention better than valproate.
What limits itDoes not cover tonic-clonic seizures; GI intolerance is common, and rare blood dyscrasias require counts.
Pearls
- Valproate instead when tonic-clonic seizures coexist.
- Hiccups, headache and behavioral change; psychosis reported.
- Rare SJS, DRESS and drug-induced lupus.
Ethosuximide prescription history
Animated chart of estimated U.S. prescriptions per year, Antiseizure meds (1869–2026). Ethosuximide enters in 1960 (estimated).
FDA-approved for
- absence seizures (~1960)
Principal riskIt does not cover tonic-clonic seizures; blood dyscrasias
Classes and tags
Clinical profile
Legacy pregnancy categoryC
Defining liabilitySedation, dizziness and agent-specific rash, behavioral, hepatic, hematologic or teratogenic toxicity.
FDA label
Read the full label on DailyMed ↗
NO BOXED WARNINGS
| FDA dosing | Population | Start | Target | Max |
|---|---|---|---|---|
| Absence (petit mal) seizures | 3-6 years | 250 mg QD | ~20 mg/kg/day | 1.5 g/day (divided) |
| Absence (petit mal) seizures | >=6 years / adult | 500 mg QD | individualized | 1.5 g/day (divided) |
Titration Increase by 250 mg every 4-7 days until control achieved
Renal Undefined
Hepatic Undefined
Instructions
- Oral
- Give higher doses (>1.5 g/day) in divided doses only under strict supervision
- May combine with other anticonvulsants if mixed seizure types coexist
Available strengths
- cap 250 mg
- sol 250 mg/5 mL
Cautions
- Blood dyscrasias (leukopenia, agranulocytosis, pancytopenia) — monitor CBC
- DRESS / multiorgan hypersensitivity
- Stevens-Johnson syndrome
- Psychiatric disturbances incl. depression and suicidal ideation
Adverse reactions
- GI: anorexia, nausea, vomiting, cramps, abdominal pain, weight loss
- Drowsiness, headache, dizziness, ataxia, hiccups
- Blood dyscrasias
- DRESS, SJS, urticaria
- Sleep disturbance, night terrors, aggressiveness
Pregnancy Undefined
Lactation Undefined
Cost
Generic entry1993
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Self-check
- Does ethosuximide treat tonic–clonic seizures?
No. - How does ethosuximide affect attention versus valproate in absence epilepsy?
Preserves attention better.