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
The anticoagulant effect of warfarin is increased by all of the following EXCEPT: 
Select and explain. 
A. Cimetidine, B. Phytonadione, C. Amiodarone, D. Phenylbutazone
B: Phytonadione
Answer: B: Phytonadione 
Explanation: Vitamin K1 (phytonadione) is the antidote of warfarin. It decreases the effect of oral anticoagulants.