3.1 Characteristics of the identified studies
The search criteria on PubMed, Web of Knowledge and Cochrane databases yielded 932 hits of which 324 were duplicates. After removal of additional 590 records (including one [21] of the two articles [21, 22] with the same sample published in different journals was excluded), 13 studies of CBZ resistance [7, 8, 13, 14, 22-30] and 8 studies of CBZ metabolism [7, 8, 17, 25, 29, 31-33] were included in the systematic review (Fig. 1). All participants in the studies were epilepsy patients and were treated with CBZ monotherapy at a stable maintenance dose. The characteristics of included studies are presented in Table 1 and 2. All the patients were treated with CBZ in a dose range of 400–1200 mg/day. The NOS scores of the included studies ranged from 5 to 8 based on the NOS evaluation system, indicating a relatively high quality of included studies. Furthermore, a test of funnel plot was not conducted due to the insufficient number of studies in the present study.