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Ethosuximide

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Ethosuximide, Zarontin

  • See Also
  1. Seizure Disorder
  • Indications
  1. Absence Seizures
  • Mechanism
  1. Succinimide anticonvulsant
  2. Partial Antagonist of T-type Calcium channels within thalamic Neurons
  3. Decreases burst firing of thalamocortical Neurons, stabilizing CNS nerve activity
  1. Therapeutic level: 40 to 100 mcg/ml
  2. Adults (and children age >6 years old)
    1. Start 500 mg orally once daily
    2. May increase dose by 250 mg/day every 4 to 7 days
    3. Maximum: 1.5 grams/day
  3. Children (ages 3 to 6 years old)
    1. Start 250 mg orally once daily
    2. May increase dose by 250 mg/day every 4 to 7 days
    3. Target dose: 20 mg/kg/day
  4. Renal Dosing (CrCl <10 ml/min)
    1. Reduce dose 25%
  • Safety
  1. Pregnancy Category C
  2. Considered Safe in Lactation
  3. Monitor Complete Blood Count (cbc), and periodic Urinalysis and Liver Function Tests
  • Metabolism
  1. Hepatic metabolism
  2. Highly Protein bound
  3. Half Life increased in liver disease and in children
  • Adverse Effects
  1. Dose dependent effects (decreases overtime with use, and with divided dosing)
    1. Nausea or Vomiting
    2. Decreased appetite (with weight loss)
    3. Sedation
  2. Serious
    1. Neutropenia (rare)
      1. Mild Leukopenia, however, is common
    2. Increased Generalized Tonic Clonic Seizures
  • Drug Interactions
  1. Valproic Acid
    1. Valproic Acid increases Ethosuximide levels
    2. Ethosuximide decreases valproic levels
  2. Phenytoin
    1. Ethosuximide increases Phenytoin levels
  3. Primidone
    1. Ethosuximide decreases Primidone levels
  • Resources
  1. Ethosuximide (DailyMed)
    1. https://dailymed.nlm.nih.gov/dailymed/lookup.cfm?setid=0d0965f7-d780-4d1c-8ecf-77387483cc02
  • References
  1. (2022) Presc Lett, Resource #361206, Antiseizure Medications
  2. Olson (2020) Clinical Pharmacology, Medmaster Miami, p. 56-7
  3. Hamilton (2020) Tarascon Pocket Pharmacopoeia