The most important principle of antiepileptic drug therapy is the selection of a medication based upon the patient's specific seizure type or epilepsy syndrome.
Medications have different efficacy for different seizure types.
Some AEDs are effective just for partial onset seizures, others for both partial and generalized onset seizures. The Veterans Administration Cooperative Studies I and II demonstrated that carbamazepine, phenytoin, valproate sodium, phenobarbital and primidone had efficacy against partial seizures. Relatively few medications have demonstrated efficacy in trials against generalized seizures. Those medications that appear to have effectiveness against both partial onset seizures and generalized onset seizure types are termed broad spectrum anticonvulsants. AEDs that appear to have broad spectrum efficacy are valproate sodium, lamotrigine, topiramate, zonisamide and felbamate.