This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Pharmacology
All the following drugs are used for thrombo prophylaxis except - 
Select and explain. 
A. Heparin, B. Warfarin, C. Aspirin, D. Antithrombin
D: Antithrombin
Answer: D: Antithrombin 
Explanation: Ans. is 'd' i.e., Antithrombin Prophylaxis for venous thrombus o Heparin (unfractioned, LM W, or fondaparinox) and oral anticoagulants (warfarin). Prophylaxis for aerial thrombus o Aspirin o Clopidogrel o Ticlopidine