There are several new antiepileptic drugs undergoing extensive clinical investigation. Five new drugs - vigabatrin, lamotrigine, gabapentin, felbamate and oxcarbazepine - appear to be the most widely tested and promising agents.
Vigabatrin is most effective in drug-resistant partial epilepsy. Vigabatrin is also effective in infantile spasms, but seems to have negative effects on myoclonic epilepsies and absence seizures. Lamotrigine and felbamate seem to be effective in partial epilepsy and in Lennox-Gastaut syndrome. In addition, lamotrigine and felbamate seem to have efficacy in idiopathic generalised epilepsies. Oxcarbazepine appears to be equally as effective as carbamazepine, but less toxic. Gabapentin has few adverse effects and has efficacy in some patients with drug-resistant partial epilepsy.
Some of the new antiepileptic drugs modify excitatory or inhibitory amino acid transmission, but some of them may employ new, still unknown mechanisms of action. Depending on the mechanism of action, the therapeutic effectiveness of the antiepileptic drugs may differ in specific epileptic syndromes. Future antiepileptic drugs may thus give us the possibility to design rational polypharmacy for individual patients by combining agents with different spectra of effectiveness. Considering the goal of good tolerability in the development of the new antiepileptic drugs, polypharmacy with these agents is not expected to increase adverse effects significantly.