The primary objective of the study is to quantify the risk of UR associated with exposure to EZG AED polytherapy in a real-world setting. Specific aims include the following:1) to describe patients receiving EZG and non-EZG AED polytherapy in terms of demographics, concomitant AED use, co-morbidities/past medical history, use of medications potentially associated with UR, and medical conditions associated with UR; 2) to determine the magnitude of the risk and time to onset of UR associated with post-marketing use of EZG AED polytherapy, and to determine the incremental risk compared with non-EZG AED polytherapy use; and 3) to determine whether the risk and time to onset of UR associated with non-EZG monotherapy use.