ethosuximide

Ethosuximide is a succinimide anticonvulsant approved for the treatment of absence seizures. It is commonly used as first-line therapy for typical absence seizures, particularly in children, and may be used as monotherapy or adjunctive therapy when absence seizures predominate.

Mechanism: The drug inhibits T-type calcium channels in thalamic neurons, reducing low-threshold Ca2+ currents and dampening thalamocortical oscillations that underlie absence seizures.

Pharmacokinetics: Ethosuximide is taken by mouth (capsules or oral suspension) and is well absorbed. It is extensively metabolized by the liver to inactive metabolites and eliminated in the urine. The elimination half-life varies with age and liver function, so dosing is adjusted accordingly.

Clinical use and dosing: Initiated at a low dose and titrated to effect; used as single agent or add-on for absence seizures. Not effective for focal or generalized tonic-clonic seizures as sole therapy.

Adverse effects: Common adverse effects include nausea, abdominal discomfort, vomiting, drowsiness, fatigue, and loss of appetite; hiccups may occur. Rashes and rare hematologic or hypersensitivity reactions can occur. As with other antiseizure medications, monitor for mood changes or behavior alterations.

Interactions and safety: Ethosuximide has relatively few clinically significant drug interactions, but concurrent use with other CNS depressants or hepatic enzyme inducers/inhibitors can alter levels. Contraindicated in hypersensitivity to ethosuximide or the succinimide class.