Ethosuximide

Actions

• Blocks low threshold T-type calcium channels in thalamic neurons.

Metabolism

Hepatic

Enzymes involved

• CYP3A4
• CYP2E1

Elimination

Renal 20%

Therapeutic serum concentration range

40-100 μg/ml

Half-life

53 hours

Plasma protein binding

0–5%

Important side-effects

Blood dyscrasias.

SLE.

Suicidal behavior and ideation.

Serious dermatologic reactions, including Stevens-Johnson syndrome.

Drug Reaction with Eosinophilia and Systemic Symptoms (DRESS).

Indications

Absence seizures.

Dosing recommendation

Start with 250 mg/day.

Increase to target dose over 1–3 weeks.

Target dose: 500–1500 mg/day divided into 2-3 doses.

Renal impairment

Insufficient data exist about ethosuximide in patients with impaired renal function.

Hepatic impairment

Insufficient data exist about ethosuximide in patients with impaired hepatic function.