Antiepileptic Drug Therapy in Patients with Drug-Resistant Epilepsy.

Antiepileptic drug (AED) therapy starts with an accurate diagnosis of epilepsy and is followed by sequential drug trials. Seizure freedom is largely achieved by the first two drug trials; thus, epilepsy that cannot be controlled after appropriately conducted trials of the first two drugs is defined as drug-resistant epilepsy (DRE). It is still unclear which mode of pharmacotherapy, among monotherapy and polytherapy, shows better outcomes in cases of DRE. However, in a recent large hospital cohort study over past two decades, combination therapy was associated with a progressive increase in seizure-free rate than monotherapy in DRE. The benefits of polytherapy in the management of DRE might be related to the recent introduction of many new AEDs with different and novel mechanisms of action and better pharmacokinetic and tolerability profiles. These new AEDs were introduced to the market after they have proven their superiority over placebos in randomized controlled trials (RCTs) on add-on therapy in patients with DRE. Therefore, polytherapy including these new AEDs in the regimen is the approved mode of treatment for cases of DRE; this has prompted physicians to try various combinations of polytherapy to optimize the clinical outcomes. In addition, the significant discrepancies in AED responder rates between RCTs and real-world practice may support the importance of judicious use of new drugs in polytherapy by experienced epileptologists. Most experts now agree to the concept of "rational polytherapy" consisting of mechanistic combinations of AEDs exerting synergistic interactions and to the importance of continuing trials of different rational polytherapy regimens to improve the outcome of the core population of epilepsy patients in the long term.