Which agent is a direct thrombin inhibitor among the direct oral anticoagulants?

• A. Rivaroxaban
• B. Apixaban
• C. Dabigatran
• D. Edoxaban

Answer: (C)

Direct thrombin inhibitors act by blocking the enzyme that directly becomes activated in the final step of clot formation. Among the direct oral anticoagulants, the agent that directly inhibits thrombin (factor IIa) is dabigatran. By binding thrombin, it prevents thrombin from converting fibrinogen to fibrin and from activating other coagulation factors, blunting clot formation at its source. The other commonly used DOACs—rivaroxaban, apixaban, and edoxaban—work upstream by inhibiting factor Xa, which stops the production of thrombin rather than inhibiting thrombin’s activity itself. So dabigatran is the direct thrombin inhibitor.