Valproate (VPA) and its valproic acid, sodium valproate, and valproate semisodium forms are medications primarily used to treat epilepsy and bipolar disorder and prevent migraine headaches. They are useful for the prevention of seizures in those with absence seizures, partial seizures, and generalized seizures. They can be given intravenously or by mouth, and the tablet forms exist in both long- and short-acting formulations.
Sodium valproate has been found to have a marked anticonvulsant activity in animals - demonstrated by the various tests used to detect antiepileptic activity - but it's mechanism of action is currently unknown.
Its anticonvulsant effect is attributed to the blockade of voltage-dependent sodium channels and increased brain levels of gamma-aminobutyric acid (GABA). The GABA-ergic effect is also believed to contribute towards the anti-manic properties of sodium valproate.
In animals, sodium valproate raises cerebral and cerebellar levels of the inhibitory synaptic transmitter, GABA, possibly by inhibiting GABA degradative enzymes, such as GABA transaminase and/or succinic semi-aldehyde dehydrogenase and/or by inhibiting the re-uptake of GABA by neuronal cells.