The use of warfarin along with aspirin has always been a “red flag” for me when reviewing drug regimens since there is an significant increase in risk for serious bleeding events as compared to the use of either alone. However, there appears to be evidence that supports the combination use, but it is limited to those with mechanical heart valves, and NOT those with atrial fibrillation alone, nor those with atrial fibrillation and other cardiovascular risk factors such as coronary heart disease and/or congestive heart failure. In fact, the author of an article in Thrombosis Research in 2011, James Douketis states that there is 1.5 to 2.0-fold increase in the risk for serious bleeding events from combination therapy as compared to warfarin alone yet no measureable benefit except in those with mechanical heart valves. He also implies that of the 800,000 people in North America that use combination therapy that the majority are most likely receiving this inappropriate treatment thereby leading to harm. The use of warfarin is one of the leading reasons for hospitalization in older adults from adverse drug events, so based on this evidence perhaps we can make a dent in those numbers by better utilizing these therapies.
Other findings from that review are:
- The use of warfarin and clopidogrel is associated with 3.08 times the risk for serious bleeding
- 40% of those on the newer anticoagulants, Xarelto and Pradaxa, are using aspirin
- Combination therapy may be appropriate for limited use in those with acute coronary syndrome, e.g. 3 months
- Combination therapy may be warranted in those where evidence is lacking, such as A. fib and coronary stent placement