 Methods. The study will use an experimental randomized open-label non-inferiority design. The population will consist of 200 adults stabilized on chronic treatment with carbamazepine, valproic acid, topiramate, oxcarbazepine, levetiracetam or lamotrigine and admitted to hospital for diagnostic evaluation or other indications, with no expected treatment changes during the subsequent 5 to 6 days. Patients will be randomized to two groups. One group will continue to receive the AED products used before enrollment brand or generic, whereas the other group will be switched to an alternative equivalent product. Dosing schedules of the AEDs being tested as well as comedications will be unaltered throughout the 6- to 7day period of the study. Serum AED levels mean of two values obtained at peak and trough, respectively in the evening and the next morning will be measured on day 1 baseline and 5 days post-randomization 6 days for patients receiving AEDs with half-lives above 12 h. The primary outcome endpoint will be the proportion of patients who, post-randomization, show a greater than 25 change in serum drug concentration compared with baseline. Secondary endpoints will include comparison of distributions of rough serum concentration changes between groups, other pharmacokinetic parameters, time to first seizure, total number of seizures, and adverse events. 