The incidence of
refractory epilepsy remains high despite the influx of many new
antiepileptic drugs (AEDs) over the past 10 years. Epidemiological data indicate that 20-40% of the patients with newly diagnosed
epilepsy will become refractory to treatment. Factors that may be used to predict whether or not a patient will respond favorably to AED
therapy include the type of
epilepsy, underlying syndrome, etiology, and the patient's history of seizure frequency, density, and clustering. Environmental factors, such as
trauma and prior
drug exposure, and genetic factors that predetermine the rate of absorption, metabolism, and uptake of a
drug by target tissue may also uniquely impact an individual and influence their response to AED
therapy. Treatment resistance is, therefore, a multifaceted phenomenon. Since individuals with
refractory epilepsy do not share a common reason for their treatment resistance, the use of targeted
drug therapies may be our best option for improving treatment outcomes in this patient population. Pharmacogeneticists are currently attempting to understand the genetic basis of
refractory epilepsy so that they can identify subgroups of patients who share a common genetic background and then target
drug therapies to meet their specific needs.