 On day 1 day of admission or day of inclusion in the study, all subjects will continue to receive their current AED treatment, without any change in formulation brand or specific generic product, route and dosing schedule. Two blood samples for the determination of the serum levels of the AEDs will be collected, one on day 1 two hours after the evening dose absorptive phase sample, close to the expected peak time and one the next morning day 2 just prior to the morning dose trough sample. 