The spectrum of the new antiepileptic drugs

Over the last decade, many new drugs have been added to the therapeutic armamentarium for epilepsy. These drugs differ considerably in their mechanisms of action and, consequently, in their spectrum of efficacy against various seizure types. Oxcarbazepine, gabapentin, tiagabine and vigabatrin are especially useful in the management of partial seizures (with or without secondary generalization) and, probably, also primarily generalized tonic-clonic seizures, with vigabatrin being of particular value also in the treatment of infantile spasms. The spectrum of efficacy of lamotrigine and topiramate is broader than that of the other drugs and includes, in addition to partial and tonic-clonic seizures, also drop attacks associated with the Lennox-Gastaut syndrome. Lamotrigine is also effective against absence seizures, while the activity of topiramate as a potential anti-absence drug has not been adequately explored. Oxcarbazepine, vigabatrin and tiagabine may aggravate myoclonic and absence seizures and, likewise, gabapentin may aggravate myoclonic seizures. Therefore, the latter drugs should not be used (or used with great caution) in patients with syndromes associated with these seizure types. Apart from differences in spectrum of efficacy, side effect profiles also differ considerably from one drug to another, with the risk of serious adverse effects limiting considerably the use of felbamate and vigabatrin. When added to preexisting therapy in patients with refractory epilepsies, the new drugs improve seizure frequency in 15% to 40% of cases, but only rarely freedom from seizures is achieved. In newly diagnosed patients, the efficacy of the new drugs is similar to that of older agents, but further studies are required to confirm the claim that the tolerability of some of these agents is superior to that of established drugs such as carbamazepine or valproate. The new antiepileptic drugs represent a useful addition to the therapeutic armamentarium, but because of limited clinical experience and cost considerations their firstline use cannot be recommended in most situations.