Contribution of hemorrhagic or thrombotic risk Any medication that impairs the platelets’ ability to function (e.g., acetylsalicylic acid, clopidogrel,nonsteroidal anti-inflammatory drugs) and is given concomitantly with warfarin may increase the risk of bleeding without affecting the INR. Conversely, certain medications (such as estrogens) increase the risk of thrombosis and their use
in patients who are taking warfarin must be carefully assessed.9