Which statement about anticoagulants is correct?

Which statement about anticoagulants is correct?

• A. Heparin prolongs the intrinsic pathway and is monitored by PTT; factors 8 and 9 are affected
• B. Warfarin prolongs the extrinsic pathway and is monitored by aPTT
• C. Heparin affects platelets to prevent aggregation
• D. Warfarin decreases clotting factors 2, 7, 9, 10 and is monitored by PT/INR

Answer: (D)

Warfarin works by inhibiting vitamin K–dependent gamma-carboxylation of clotting factors II, VII, IX, and X (and proteins C and S). Because factor VII has the shortest half-life, this inhibition lengthens the extrinsic pathway quickly, which is reflected by an increased prothrombin time. That’s why warfarin therapy is monitored with PT and the INR, which standardizes results across labs. Heparin, in contrast, accelerates antithrombin III and mainly prolongs the intrinsic pathway, typically monitored by the aPTT. It does not primarily target platelet aggregation. The statement about factors 8 and 9 being specifically affected isn’t the precise way heparin’s effect is described. The claim that warfarin prolongs the extrinsic pathway but is monitored by aPTT is incorrect; the correct monitoring test for warfarin is PT/INR.

Warfarin works by inhibiting vitamin K–dependent gamma-carboxylation of clotting factors II, VII, IX, and X (and proteins C and S). Because factor VII has the shortest half-life, this inhibition lengthens the extrinsic pathway quickly, which is reflected by an increased prothrombin time. That’s why warfarin therapy is monitored with PT and the INR, which standardizes results across labs.

Heparin, in contrast, accelerates antithrombin III and mainly prolongs the intrinsic pathway, typically monitored by the aPTT. It does not primarily target platelet aggregation. The statement about factors 8 and 9 being specifically affected isn’t the precise way heparin’s effect is described.

The claim that warfarin prolongs the extrinsic pathway but is monitored by aPTT is incorrect; the correct monitoring test for warfarin is PT/INR.