Which pharmacologic agent is used for DVT prophylaxis in moderate to high-risk patients after surgery?

• A. Aspirin
• B. Warfarin
• C. Low molecular weight heparin (enoxaparin)
• D. Unfractionated heparin

Answer: (C)

Low molecular weight heparin (enoxaparin) is the preferred pharmacologic DVT prophylaxis after surgery in moderate to high-risk patients. It provides effective, predictable anticoagulation with subcutaneous administration and fixed dosing, so routine lab monitoring isn’t needed. It also has a lower risk of heparin-induced thrombocytopenia compared with unfractionated heparin and is convenient for the perioperative setting.

Aspirin is less effective for venous thromboembolism prophylaxis in high-risk postoperative patients. Warfarin isn’t used for immediate post-op prophylaxis because it has a slow onset, requires bridging, and needs INR monitoring with dietary and drug interactions. Unfractionated heparin can be used in select situations (e.g., renal impairment or when rapid reversal is needed) but requires IV administration and frequent aPTT monitoring and carries a higher HIT risk, making it less convenient than LMWH for routine prophylaxis.