Mechanisms of antiepileptic drug action.

Animal seizure models, in vitro preparations of cell cultures and tissue slices, and an unravelling of some of the basic mechanisms underlying epileptogenesis and epilepsy have furthered the understanding of mechanisms of action of antiepileptic drugs at the cellular and subcellular levels. Nevertheless, the mechanism of action of most antiepileptic drugs in clinical use is incompletely understood. Multiple physiologic mechanisms are altered by antiepileptic drugs. Some of these drugs, such as phenytoin and carbamazepine, decrease sustained repetitive firing and post-tetanic potentiation through their blocking effects on the sodium channel. Benzodiazepines and barbiturates enhance GABA-mediated inhibition. Many antiepileptic drugs inhibit calcium influx and calcium-mediated secondary effects at supratherapeutic concentrations. Newer drugs that inhibit excitatory receptors or enhance various forms of inhibition are presently under investigation.