Succinimides

Succinimides

The succinimides, ethosuximide and methsuximide, are used to manage absence seizures. Ethosuximide is considered the drug of choice for absence seizures.

Pharmacokinetics

The succinimides are readily absorbed from the GI tract and me-tabolized in the liver and excreted in urine. Metabolites are believed to be inactive. The elimination half-life of ethosuximide is about 60 hours in adults and 30 hours in children.

Pharmacodynamics

Ethosuximide’s exact mechanism of action is unknown. It’s thought to inhibit an enzyme necessary for the formation of gamma-hydroxybutyrate, which has been associated with the induction of absence seizures.

Pharmacotherapeutics

In addition to being the drug of choice for treating absence seizures, ethosuximide may also be used in combination with valproic acid for hard-to-control absence seizures.

Drug interactions

Ethosuximide isn’t protein-bound, so displacement reactions can’t occur. Carbamazepine may induce the metabolism of ethosux- imide. Valproic acid may inhibit the metabolism of ethosuximide only if the metabolism is near saturation. (See Adverse reactions to succinimides.)