Ethosuximide
Class: Antiepileptic (T-type calcium channel blocker)
Indications
- First-line drug for absence seizures (petit mal)
- Not effective for tonic-clonic or focal seizures
Mechanism of Action
- Inhibits T-type calcium channels in thalamic neurons
- Suppresses abnormal cortical–thalamic rhythms that cause absence seizures
Dosage
- Children: Start 10–15 mg/kg/day orally in 2 doses; increase gradually up to 20–30 mg/kg/day (max 1500 mg/day)
- Adults: Start 250 mg twice daily; increase to 500–1500 mg/day in divided doses
Major Side Effects
- GI upset (nausea, vomiting, abdominal pain)
- Lethargy, dizziness, headache
- Irritability, behavioral changes (rare psychosis)
- Bone marrow suppression (rare)
- Stevens–Johnson syndrome (rare)
Contraindications
- Hypersensitivity to ethosuximide
- Caution in patients with hepatic or renal impairment
- History of bone marrow depression
Compatible Solvent / Administration
- Oral capsules or syrup
- Administer with food or milk to reduce GI upset
Special Precautions
- Monitor CBC periodically (risk of blood dyscrasias)
- Monitor mental status and mood changes
- Withdraw gradually to avoid rebound seizures
- Pregnancy Category C – use with caution
Key Point: Ethosuximide is the drug of choice for absence seizures, safe and effective but requires monitoring for rare hematologic and psychiatric side effects.