Classifications: central nervous system agent; succinimide anticonvulsant
Pregnancy Category: C


250 mg capsules; 250 mg/5 mL syrup


Succinimide anticonvulsant. Usually ineffective in management of psychomotor or major motor seizures.

Therapeutic Effects

Reduces frequency of epileptiform attacks, apparently by depressing motor cortex and elevating CNS threshold to stimuli.


Management of absence (petit mal) seizures, myoclonic seizures, and akinetic epilepsy. May be administered with other anticonvulsants when other forms of epilepsy coexist with petit mal.


Hypersensitivity to succinimides; severe liver or kidney disease; use alone in mixed types of epilepsy (may increase frequency of grand mal seizures). Safety during pregnancy (category C), lactation, or in children <3 y is not established.

Route & Dosage

Absence Seizures
Adult/Child: PO 6–12 y, 250 mg b.i.d., may increase q4–7d prn (max: 1.5 g/d)
Child: PO 3–6 y, 250 mg/d, may increase q4–7d prn (max: 1.5 g/d)



Adverse Effects (1%)

CNS: Drowsiness, hiccups, ataxia, dizziness, headache, euphoria, restlessness, irritability, anxiety, hyperactivity, aggressiveness, inability to concentrate, lethargy, confusion, sleep disturbances, night terrors, hypochondriacal behavior, muscle weakness, fatigue. Special Senses: Myopia. GI: Nausea, vomiting, anorexia, epigastric distress, abdominal pain, weight loss, diarrhea, constipation, gingival hyperplasia. Urogenital: Vaginal bleeding. Hematologic: Eosinophilia, leukopenia, thrombocytopenia, agranulocytosis, pancytopenia, aplastic anemia, positive direct Coombs' test. Skin: Hirsutism, pruritic erythematous skin eruptions, urticaria, alopecia, erythema multiforme, exfoliative dermatitis.


Drug: Carbamazepine decreases ethosuximide levels; isoniazid significantly increases ethosuximide levels; levels of both phenobarbital and ethosuximide may be altered with increased seizure frequency. Herbal: Ginkgo may decrease anticonvulsant effectiveness.


Absorption: Readily absorbed from GI tract. Peak: 4 h; steady state: 4–7 d. Metabolism: Metabolized in liver. Elimination: Excreted slowly in urine; small amounts excreted in bile and feces. Half-Life: 30 h in children, 60 h in adults.

Nursing Implications

Assessment & Drug Effects

Patient & Family Education

Common adverse effects in italic, life-threatening effects underlined; generic names in bold; classifications in SMALL CAPS; Canadian drug name; Prototype drug