A 25-year-old woman with juvenile myoclonic epilepsy is started on sodium valproate. Which COMBINATION of mechanisms best explains its broad-spectrum antiseizure activity?

• A Selective blockade of T-type Ca2+ channels in thalamic neurons only
• B NMDA receptor antagonism + inhibition of carbonic anhydrase
• C Inhibition of voltage-gated Na+ channels + enhancement of GABA via inhibition of GABA-T and succinic semialdehyde dehydrogenase ✓
• D Blockade of voltage-gated K+ channels + inhibition of glutamate release

Explanation

Sodium valproate exerts antiseizure effects through multiple mechanisms: it blocks voltage-gated sodium channels (reducing high-frequency firing), inhibits T-type calcium channels (relevant for absence seizures), and increases cerebral GABA concentrations by inhibiting GABA transaminase (GABA-T) and succinic semialdehyde dehydrogenase—enzymes responsible for GABA catabolism. This multi-mechanistic profile explains its efficacy across multiple seizure types including generalized tonic-clonic, absence, and myoclonic seizures. Ethosuximide (not valproate) exclusively targets T-type calcium channels for absence seizures.

Reference: KD Tripathi, Essentials of Medical Pharmacology, 8th ed.

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Written and medically reviewed by the StethoPrep medical team.