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
Anticoagulant not used in vitro is - 
Select and explain. 
A. Heparin, B. Warfarin, C. Oxalate, D. Citrate
B: Warfarin
Answer: B: Warfarin 
Explanation: Ans. is 'b' i.e., Warfarin o Oral anticoagulants have only in vivo action (not in vitro). o Heparin is used both in vivo and in vitro. o Oxalate and citrate are used in vivo.