Pharmacology General 032b03d0 The anticoagulant effect of warfarin is increased by all of the following EXCEPT: A Cimetidine B Phytonadione C Amiodarone D Phenylbutazone High-Yield Explanation Vitamin K1 (phytonadione) is the antidote of warfarin. It decreases the effect of oral anticoagulants.