[Antiepileptic drugs: mechanism of action]

Great progress has been made in the development of antiepileptic drugs (AEDs) from their early empirical stage until the current scientifically-founded advancement based on our greater understanding of the genesis of epilepsy. Available AEDs decrease neuronal membrane excitability, acting on ion channels or synaptic receptors. The classic AEDs act on sodium channels (phenytoin and carbamazepine); increase GABA-A receptor-mediated inhibition (benzodiazepines and barbiturates); and on T-type Ca2+ channels (sodium valproate and ethosuximide). Many patients are resistant to these AEDs. The introduction of new drugs whose mechanisms of action are not well established has improved therapeutic prospects. Four promising new AEDs are now available in many countries. Vigabatrin is an irreversible inhibitor of GABA transaminase. Lamotrigine blocks Na+ channels, thereby inhibiting the presynaptic release of excitatory neurotransmitters. Gabapentin increases GABAergic inhibition and Felbamate acts on the NMDA receptor and Na+ channels. New techniques in molecular biology are likely to facilitate the design of better AEDs.