Direct thrombin inhibitors include which drug?

• A. Heparin
• B. Enoxaparin
• C. Argatroban
• D. Dalteparin

Answer: (C)

Direct thrombin inhibitors bind thrombin directly at its active site, blocking its ability to convert fibrinogen to fibrin and to activate platelets. Argatroban is a classic example of this mechanism and is used when anticoagulation is needed in patients with heparin-induced thrombocytopenia, since it does not rely on antithrombin. The other drugs listed are indirect inhibitors: heparin and low-molecular-weight heparins like enoxaparin and dalteparin work by enhancing antithrombin III, which then inhibits thrombin (and factor Xa). They don’t bind thrombin directly. Hence, Argatroban is the direct thrombin inhibitor in this set.