Until recently, epidemiological researches on drug-resistant epilepsy were hampered by a lack of defined criteria. In 2010, the International League Against Epilepsy (ILAE) appointed a taskforce to define drug resistant epilepsy as “the failure of adequate trials of two tolerated, appropriately chosen and used antiepileptic drug schedules to achieve sustained seizure freedom.” There is some disagreement over what constitutes a sufficient dosage. As noted in the ILAE study, dogmatically defining the optimal dose for each medication when administered for a specific individual is impracticable. While there is preliminary evidence to support using half of the stated daily dosage as a cut-off in adults, a documented attempt to titrate the dose to a clinically useful dose range should be highlighted. It is also known that medication resistance is dynamic, with some patients experiencing intermittent periods of seizure independence and relapse. As a result, applying the criteria to a particular moment in a patient’s history may reflect a snapshot in their epilepsy trajectory.
