National estimates of emergency department visits for hemorrhage-related adverse events from clopidogrel plus aspirin and from warfarin.

BACKGROUND: Dual antiplatelet therapy (DAT) with clopidogrel plus aspirin is a well-established antithrombotic strategy, with hemorrhage being the chief adverse event (AE) of concern. Outside of clinical trials, few published data describe the magnitude and nature of hemorrhage-related AEs from DAT.

METHODS: To estimate the numbers and rates of emergency department (ED) visits for hemorrhage-related AEs (hemorrhage or evaluation for potential hemorrhage) from DAT in the United States and put them in the context of those from warfarin, we analyzed AEs from the National Electronic Injury Surveillance System-Cooperative Adverse Drug Event Surveillance project, 2006-2008, and outpatient prescribing from the National Ambulatory Medical Care Survey and the National Hospital Ambulatory Medical Care Survey, 2006-2007.

RESULTS: Based on 384 cases, there were an estimated 7654 (95% confidence interval [CI], 3325-11 983) ED visits annually for hemorrhage-related AEs from DAT compared with 2926 cases and an estimated 60 575 (36 117-85 033) ED visits from warfarin. Approximately 60% of ED visits for DAT consisted of epistaxis or other minor hemorrhages (eg, bleeding from small cuts). The risk of hospitalization for ED visits involving acute hemorrhages was not significantly different between DAT and warfarin (risk ratio, 0.73; 95% CI, 0.38-1.08). The estimated rate of ED visits involving acute hemorrhages from DAT was 1.2 per 1000 outpatient prescription visits vs 2.5 per 1000 outpatient prescription visits for warfarin (risk ratio, 0.49; 95% CI, 0.15-0.83).

CONCLUSIONS: These findings indicate that the acute hemorrhagic risk with DAT is clinically significant and reinforce the importance of practitioners and patients recognizing and anticipating this risk.