Meili Lin,1 Yi He,1 Ping He,1 Hongyan Jiang,1 Huan Luo,1 Haibin Dai,1,2 Lingyan Yu1,2 1Department of Pharmacy, Second Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang Province, People’s Republic of China; 2Research Center for Clinical Pharmacy, Zhejiang University, Hangzhou, Zhejiang Province, People’s Republic of ChinaCorrespondence: Haibin Dai; Lingyan Yu, Department of Pharmacy, Second Affiliated Hospital, Zhejiang University School of Medicine, 88th Jiefang Road, Hangzhou, Zhejiang, People’s Republic of China, Email haibindai@zju.edu.cn; lingyanyu@zju.edu.cnBackground: The integration of Clinical Decision Support Systems (CDSSs) into the prescription review process is expected to mitigate medication errors and increase patient safety. This study aimed to quantify the impact of integrating the CDSS into the prescription review process.Methods: This retrospective study was conducted by pharmacists at a 3200-bed tertiary hospital in China, leveraging data from the Hospital Information System and CDSS software across two distinct periods: August 2021 to July 2022 (preimplementation) and August 2022 to July 2023 (postimplementation). The chi-square test was used to compare the proportions of medication alerts and patients receiving alerts, both overall and per ward, before and after implementation. The chi-square test was also used to assess the significance of differences in medication alert deviations and pharmacist interventions between the two groups.Results: During the pre- and postimplementation periods, 5,170,765 and 5,804,595 medication orders were prescribed, respectively. Among these, 130,286 (2.52%) and 133,562 (2.30%) prescriptions triggered alerts, indicating a significant reduction in the alert rate of 0.22% (aHR=0.911, 95% CI 0.904– 0.918; P< 0.001). Difference in the distribution of the top ten medication alert categories was observed between the two periods. In the pre- and postimplementation groups, 208,356 and 218,165 patients were prescribed medication, respectively. Among them, 63,219 (30.34%) and 61,258 (28.08%) patients received alerts, respectively, showing a significant reduction of 2.26% (aHR=0.896, 95% CI 0.885– 0.908; P< 0.001). Among the clinical wards, 66.09% (76 out of 115) showed significant differences in the proportion of patients receiving alerts between the pre- and postimplementation periods (P< 0.05). Specifically, 45.22% (52 out of 115) of these wards experienced a decrease in the proportion of patients receiving alerts, whereas a smaller percentage, 20.87% (24 out of 115), experienced an increase.Conclusion: CDSSs are invaluable tools for hospital pharmacists and physicians, assisting in the complex task of prescription review.Keywords: CDSS, prescription review, medication alerts, patient safety