Morrow RL, et al. - In this study involving 96,753 patients with seizure and 888,540 matched controls, researchers investigated the risk of seizure with tramadol relative to the comparable opioid analgesic codeine. This retrospective study sample consisted of US adults with employer-sponsored and government-sponsored health benefits. No association was found between tramadol and an increased risk of seizure, which was defined by inpatient and outpatient diagnoses. This finding, however, was sensitive to the outcome definition used and warrants further study.