Introduction: The nature of medication errors (MEs) and the frequency of identified or intercepted MEs are not being scrutinized in daily practice in Japan.
Objectives: The aim of this study was to clarify the epidemiology of MEs and the risk factors for non-intercepted and unidentified MEs.
Methods: The Japan Adverse Drug Events (JADE) study was a prospective cohort study carried out at three tertiary-care teaching hospitals in Japan. Participants were consecutive patients (N = 3459) aged ≥15 years who were admitted to the study wards. MEs were identified by on-site reviews of all medical charts, self-reports, and prescription queries by pharmacists. Two independent physicians reviewed and classified all MEs and adverse drug events and determined the stages at which the MEs occurred and whether there was interception or identification of the MEs.
Results: A total of 514 MEs were observed among 433 patients. Sixty-four percent of MEs occurred at the ordering stage. Among these, 60 % were due to duplicate drug orders. Overall, 63 % and 45 % of MEs were not intercepted or identified during hospitalization, respectively. The independent risk factors for non-intercepted MEs were hospitalization in the surgical ward (odds ratio [OR] 2.94) and the intensive care unit (OR 3.57). MEs by resident physicians were more likely to be intercepted (OR 0.52 for non-intercepted MEs).
Conclusions: MEs frequently occurred and most at the ordering stage. Almost half of MEs were not intercepted or identified. Many MEs at the later stages were less likely to be intercepted and resulted in actual patient harm. Systems to improve the identification and interception of MEs should be implemented.