 If a change in dose of the AEDs being tested or any potentially interacting comedication is necessary prior to day 56, the two post-randomization samples may be collected 24 h earlier for AEDs with half lives of about 12 h or less carbamazepine, levetiracetam, valproic acid, topiramate combined with enzyme inducers, MHD, and lamotrigine combined with enzyme inducers. Because in these patients the half-life of the AED being tested allows attainment of steady-steady conditions within 72 h. After collection of the post-randomization samples, the subject will exit the study. In all other situations requiring premature termination of the allocated treatment, subjects will exit the study and will be considered as drop-outs with no evaluable pharmacokinetic outcome data. 