About Valproic Acid Histone Deacetylase Inhibitor ,a GABA transaminase inhibitor, Anticonvulsant, Antimanic,migraine prophylactic. Mechanism of Action of Valproic Acid Valproic acid prolongs the inactivated state of voltage sensitive neuronal sodium ion channel either by increasing the efflux or by decreasing the influx of sodium ion across the cell membrane and inhibits the high frequency neuronal discharge. It blocks the propagation of neuronal impulses. It also modulates neurotransmitter release and neuronal bursting through an effect on voltage gated and receptor gated calcium channels. Valproic acid enhances the release and synthesis of inhibitory neurotransmitter GABA and inhibits its degradation. This will result in an increased concentration of GABA and is used as antiepileptic agent. Valproate is also used to treat the acute manic phase of bipolar disorder and for the prophylaxis of migraine.