Which anticoagulant drug's efficacy is affected by vitamin E toxicity?

The correct choice is warfarin, as its efficacy is influenced by vitamin E toxicity. Warfarin is an oral anticoagulant that functions as a vitamin K antagonist, inhibiting the synthesis of vitamin K-dependent clotting factors, which include factors II, VII, IX, and X.

Vitamin E can act as an antioxidant and, at high levels, may interfere with vitamin K metabolism, thus affecting the action of warfarin. Specifically, vitamin E can prolong the anticoagulant effects of warfarin by decreasing the availability of vitamin K, potentially leading to an increased risk of bleeding. This interaction underscores the importance of monitoring patients on warfarin for changes in vitamin intake, including vitamin E, as it can alter the anticoagulant response.

In comparison, heparin works via a different mechanism, primarily by activating antithrombin III to inhibit thrombin and factor Xa, and is not directly affected by vitamin E levels. Aspirin, an antiplatelet agent, inhibits platelet aggregation but is not influenced by vitamin K or vitamin E. Rivaroxaban, a direct factor Xa inhibitor, also operates independently of vitamin K and is not affected by vitamin E toxicity. Understanding these mechanisms is crucial for managing anticoag