ORAL ANTICOAGULATION with a vitamin K (phytonadione) antagonist has always been a problematic therapy. The risk of serious bleeding is substantial (2%-3% yearly) and does not decrease over time. In fact, as patients undergoing long-term therapy age, the bleeding risk increases. The therapeutic effect of oral anticoagulation falls in a narrow range between increased risk of thrombosis when the international normalized ratio (INR) is too low and increased bleeding risk when it is too high.
Hyers TM. Duration of Anticoagulation in Venous Thromboembolism. Arch Intern Med. 2003;163(11):1265-1266. doi:10.1001/archinte.163.11.1265