New and investigational antiepilepsy drugs

Abstract

Despite reasonably good drugs for epilepsy, about 25 to 50% of patients with epilepsy have seizures which are difficult to control, or experience deleterious side effects or drug-drug interactions. Thus, antiepilepsy drugs (AEDs) with greater efficacy, more tolerability and fewer interactions are needed. Most newer drugs are designed to affect specific areas of apparent epileptogenesis. Among the seven drugs summarised in this review, clobazam, vigabatrin and tiagabine interact with GABA receptors; lamotrigine and topiramate interact with sodium channels; and gabapentin and felbamate appear to have other, at present unknown, mechanisms of action. The arbitrary standard of efficacy for new AEDs is the percentage of patients achieving at least a 50% reduction in seizures. Because patients suitable for efficacy trials have seizures which are difficult to treat with available AEDs, drugs which reduce seizures demonstrate important effectiveness. Felbamate has recently been approved in the United States for treatment of partial seizures in adults and Lennox-Gastaut syndrome in children. Gabapentin has recently been approved for the adjunctive treatment of complex partial seizures. Lamotrigine and vigabatrin were recently approved in several European countries.