Classifications: succinimide anticonvulsant;
Therapeutic: anticonvulsant

Pregnancy Category: C


250 mg capsules; 250 mg/5 mL syrup


Succinimide anticonvulsant that reduces the current in T-type calcium channel found on primary afferent neurons. Activation of the T channel causes low-threshold calcium spikes in neurons, believed to play a role in the spike-and-wave pattern observed during petit mal seizures.

Therapeutic Effect

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; bone marrow suppression; use alone in mixed types of epilepsy (may increase frequency of grand mal seizures); pregnancy (category C), children <3 y.

Cautious Use

Hematologic disease; preexisting hepatic disease; intermittent porphyria; renal disease.

Route & Dosage

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


  • Give with food if GI distress occurs.
  • Store all forms at 15°–30° C (59°–86° F); capsules in tight containers, and syrup in light-resistant containers; avoid freezing.

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 from GI tract. Peak: 4 h; steady state: 4–7 d. Metabolism: In liver. Elimination: In urine; small amounts in bile and feces. Half-Life: 30 h (child), 60 h (adult).

Nursing Implications

Assessment & Drug Effects

  • Lab tests: Perform baseline and periodic hematologic studies, liver and kidney function.
  • Monitor adverse drug effects. GI symptoms, drowsiness, ataxia, dizziness, and other neurologic adverse effects occur frequently and indicate the need for dosage adjustment.
  • Observe closely during period of dosage adjustment and whenever other medications are added or eliminated from the drug regimen. Therapeutic serum levels: 40–80 mcg/mL.
  • Observe patients with prior history of psychiatric disturbances for behavioral changes. Close supervision is indicated. Drug should be withdrawn slowly if these symptoms appear.

Patient & Family Education

  • Discontinue drug only under physician supervision; abrupt withdrawal of ethosuximide (whether used alone or in combination therapy) may precipitate seizures or petit mal status.
  • Do not drive or engage in other potentially hazardous activities until response to drug is known.
  • Monitor weight on a weekly basis. Report anorexia and weight loss to physician; may indicate need to reduce dosage.

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

© 2006-2023 Last Updated On: 02/01/2023 (0)
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