Adverse drug events in the outpatient setting: an 11-year national analysis

Purpose Adverse drug events (ADEs) are a common complication of medical care resulting in high morbidity and medical expenditure. Population level estimates of outpatient ADEs are limited. Our objective was to provide national estimates and characterizations of outpatient ADEs and determine risk factors associated with these events. Methods Data are from the National Center for Health Statistics which collects information on patient visits to outpatient clinics and emergency departments throughout the United States. We examined visits between 1995 and 2005 and measured the national annual estimates of and risk factors for outpatient ADEs requiring medical treatment. Results The national annual number of ADE‐related visits was 4 335 990 (95%CI: 4 326 872–4 345 108). Visits for ADEs to outpatient clinics increased over the study period from 9.0 to 17.0 per 1000 persons (p‐value for trend