NAPLEX Practice Question # 86

NAPLEX Examination.

Practice Question # 86.


tonicclonic seizure

Ethosuximide (Zarontin)

Mechanism of action

  • Ethosuximide may inhibit the sodium–potassium adenosine triphosphatase (Na/K ATPase) system and the reduced form of nicotinamide adenine dinucleotide phosphate (NADPH) linked aldehyde reductase (which is necessary for the formation of [1]- hydroxybutyrate, which is associated with the induction of absence seizures).
  • Ethosuximide reduces or eliminates the EEG abnormality; however, absence seizures are the only seizures in which the normal EEG has clinical value (i.e., when the EEG abnormality is corrected, the seizures are also controlled).
  • Ethosuximide is a relatively benign anticonvulsant with minimum protein binding.

Administration and dosage.

  • Ethosuximide is usually given orally in an initial dose of 500 mg daily in adults and older children and 250 mg daily in children ages 3 to 6 years. Th e dose may be raised by 250 mg every week to a maximum of 1.5 g daily in adults.

Precautions and monitoring effects

  • Blood dyscrasias have been reported, making periodic blood counts necessary.
  • Th ere have been reports of hepatic and renal toxicity; thus periodic renal and liver function monitoring is necessary.
  • Cases of systemic lupus erythematosus have been reported.

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