<prompt> Which of the following antiepileptic drugs acts by affecting the levels of GABA?Sodium valproateEthosuximidePhenytoin sodiumCarbamazepine  <response>: Ans. A Sodium valproateRef: KDT 8e p444It acts by various mechanisms like increase in GABA, blockade of Na channels and inhibition of T-type Ca2 currents. Valproate increases the formation of GABA by stimulating glutamic acid decarboxylase and inhibits the degradation of GABA by inhibiting GABA transaminase and succinic semialdehyde dehydrogenase.Phenytoin and carbamazepine acts by affecting neuronal Na channels.Ethosuximide acts by affecting T-type Ca2 currents. 