Risk factors for bleeding in patients taking coumarins.

Coumarins (e.g., warfarin) are used for the treatment and prophylaxis of venous and arterial thromboembolism. Unfortunately, their use is limited by bleeding. In deciding whether to initiate coumarin therapy, the therapeutic benefits must be weighed against the potential risk of bleeding for each individual patient. The major determinants of coumarin-related bleeding are the intensity of anticoagulant effect as measured by the International Normalized Ratio, patient characteristics, concomitant use of other drugs, and the length of anticoagulant therapy. At the initiation of coumarin therapy, the risk factors for bleeding can be identified by the COUMARINS acronym and by one of the bleeding prediction models. During ongoing therapy with coumarins, the risks and benefits of therapy should be reassessed periodically. This article reviews the current evidence for the prediction and prevention of coumarin-related bleeding.