Which of the following is a valid inpatient thromboprophylaxis option?

• A. Aspirin
• B. Warfarin
• C. Rivaroxaban
• D. Heparin

Answer: (D)

When preventing venous thromboembolism in hospitalized patients, you want an anticoagulant that acts quickly and predictably. Heparin given by injection—whether unfractionated or as low-molecular-weight heparin—provides rapid, reliable protection during the inpatient stay and has a short, manageable effect if bleeding occurs. Aspirin isn’t effective for preventing venous clots because it targets platelets and arterial thrombosis rather than the coagulation cascade. Warfarin has a delayed onset and requires INR monitoring, making it unsuitable for immediate inpatient prophylaxis. Rivaroxaban, a direct oral anticoagulant, is used in select settings (like certain orthopedic prophylaxis) but is not the standard inpatient option in many institutions due to considerations around dosing, monitoring, and bleeding risk. Therefore, heparin is the appropriate inpatient thromboprophylaxis choice.