Warfarin produces its anticoagulant effect by which primary molecular mechanism?

• A Direct inhibition of thrombin (factor IIa) at its active site
• B Inhibition of vitamin K epoxide reductase, preventing gamma-carboxylation of factors II, VII, IX and X ✓
• C Potentiation of antithrombin III-mediated inactivation of factor Xa
• D Irreversible acetylation of cyclooxygenase-1 in platelets

Explanation

Warfarin blocks vitamin K epoxide reductase (VKORC1), depleting reduced vitamin K needed by gamma-glutamyl carboxylase. Without gamma-carboxylation, factors II, VII, IX, X and proteins C and S cannot bind calcium and phospholipid membranes. Option A describes dabigatran, option C describes heparins, and option D describes aspirin, so each distractor maps to a different drug class.

Reference: Katzung Basic and Clinical Pharmacology, 15th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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