Ethosuximide is the first-line drug for absence seizures. It is effective only for this seizure type.
Also known as: zarontin
Selective antiepileptic activity for primary absence seizures. Inhibits T-type Ca²⁺ currents in the thalamus.
Selective blockade of T-type Ca²⁺ currents in thalamic neurons, interrupting the 3 Hz oscillatory activity that sustains absence seizures.
Complete and rapid oral absorption. Bioavailability: 100%. Peak: 1-4 h. Food does not affect absorption.
Metabolised by CYP3A4 (70%) and CYP2E1. Inactive metabolites. Does not induce CYP.
40-60 h (adults), 30 h (children).
DailyMed/FDA — Zarontin; EMC-UK — Ethosuximide
DailyMed/FDA — Zarontin; EMC-UK
Antiepileptic + antiepileptic: valproate may increase ethosuximide levels.
Valproate inhibits CYP3A4, one of the metabolic pathways for ethosuximide. Levels may increase 20-30%.
Ethosuximide levels, signs of toxicity.
Monitor ethosuximide levels if combined with valproate.
DailyMed/FDA; EMC-EMC PT
No documented food or drink interactions.
No documented disease interactions.
No documented pregnancy or breastfeeding information.
Clinical and educational support tool. The information does not replace a medical prescription or the opinion of a qualified healthcare professional.
Medicines from the same therapeutic group (ATC classification) or the same pharmacological class.
