Warfarin and antiplatelet combination use among commercially insured patients enrolled in an anticoagulation management service

Background: Although warfarin and antiplatelet medications have documented efficacy for prevention of primary and secondary cardiovascular events, the appropriateness of warfarin and antiplatelet combination therapy is not well described in national consensus guidelines. Methods and results: Cross-sectional data from 4,557 Kaiser Permanente Colorado members >= 18 years old who were receiving warfarin anticoagulation therapy were used to quantify the prevalence of warfarin and antiplatelet agent (ie, aspirin, clopidogrel, dipyridamole, and/or dipyridamole/aspirin) combination therapy as of September 30, 2005, and to identify characteristics of patients receiving combination therapy. The prevalence of warfarin and any antiplatelet combination therapy was 385/1,000 (95% confidence interval [CI], 371/1,000 to 399/1,000). The majority of combination therapy was warfarin and aspirin (prevalence, 378/1,000) with a daily dose of aspirin, 81 mg, being the most reported dose (prevalence, 328/1,000). Patients receiving combination therapy were more likely to be male (63.6% vs 46.4%; adjusted odds ratio, 1.5; 95% CI, 1.3 to 1.7) and have a comorbidity of heart failure (29.0% vs 15.6%; adjusted odds ratio, 1.2; 95% CI, 1.1 to 1.5), coronary artery disease (62.4% vs 17.5%; adjusted odds ratio, 7.6; 95% CI, 6.5 to 8.8), and/or stroke/transient ischemic attack (5.2% vs 1.6%; adjusted odds ratio, 3.5; 95% CI, 2.3 to 5.3). Conclusion: Nearly 4 of 10 patients receiving warfarin management care were receiving warfarin and antiplatelet combination therapy. The findings suggest that this practice is widespread, especially among patients with established cardiovascular disease, and involves a substantially higher number of patients than previously reported. The clinical outcomes associated with this practice require further investigation.