A 65-year-old patient with elevated PT/INR and suspected intracranial bleed; on oral blood thinners but the medications are not with her and she cannot communicate. Which medication would be suspected?

• A. Plavix
• B. Aspirin
• C. Coumadin
• D. Enoxaparin

Answer: (C)

The main idea is that PT/INR specifically reflects the extrinsic pathway of coagulation and is most affected by an oral vitamin K antagonist. Coumadin (warfarin) inhibits vitamin K–dependent clotting factors II, VII, IX, and X, which prolongs the prothrombin time and raises the INR. In a patient with suspected intracranial bleeding who is on an oral anticoagulant, a high INR points to warfarin as the likely medication in use.

Aspirin and Plavix are antiplatelet drugs; they impair platelet function and increase bleeding risk but do not shorten or lengthen the PT/INR. Enoxaparin is a low‑molecular‑weight heparin given by injection and more commonly affects the aPTT/anti‑Xa tests rather than the PT/INR. Therefore, the pattern described fits warfarin, the oral anticoagulant.