Although the prognosis for the majority of patients with epilepsy is good, up to 30% of patients continue to have seizures despite carefully optimized antiepileptic drug (AED) treatment[77] Two principal theories, alterations in drug penetration to the brain and alterations in drug targets, have been suggested to play a role in therapeutic failure in this population[78] Several studies have demonstrated a significant association between MDR1 polymorphisms and PGP expression in patients with drug-resistant epilepsy [Table 2]. The gene discussed is PGP; the disease is epilepsy.