Overview
Ethosuximide is an anticonvulsant medication primarily used to treat absence seizures (petit mal epilepsy). It is considered a first-line treatment for this condition and works by reducing abnormal electrical activity in the brain.
Mechanism of Action
Ethosuximide selectively inhibits T-type calcium channels in thalamic neurons, reducing low-threshold calcium currents that are involved in generating the spike-wave patterns characteristic of absence seizures. This action suppresses the abnormal neuronal synchronization in thalamocortical circuits.
Indications
- Treatment of absence seizures (petit mal epilepsy)
- May be used as adjunctive therapy for other seizure types when absence seizures are present
Dosage
Initial dose: 500 mg/day (250 mg twice daily for adults and children over 6 years). Maintenance dose: Usually 20 mg/kg/day. Maximum dose: 1.5 g/day. Dosage should be individualized based on patient response and tolerance. For children 3-6 years: Initial dose 250 mg/day, increase as needed.
Contraindications
- Hypersensitivity to ethosuximide or any component of the formulation
- Patients with a history of blood dyscrasias
- Severe hepatic or renal impairment
Side Effects
- Common: Gastrointestinal disturbances (nausea, vomiting, anorexia, abdominal pain)
- Common: CNS effects (drowsiness, dizziness, headache, fatigue)
- Common: Behavioral changes (irritability, aggression, depression)
- Serious: Blood dyscrasias (leukopenia, agranulocytosis, pancytopenia)
- Serious: Stevens-Johnson syndrome, toxic epidermal necrolysis
- Serious: Lupus-like syndrome
- Other: Hiccups, photophobia, rash, urticaria
Interactions
- Valproic acid: May increase ethosuximide levels
- Phenytoin, carbamazepine: May decrease ethosuximide levels
- CNS depressants (alcohol, benzodiazepines, opioids): Additive CNS depression
- Oral contraceptives: May reduce contraceptive effectiveness
- Warfarin: May alter anticoagulant effect