<prompt> Dicumarol interferes with -Vitamin KAntithrombinPlateletsPlasminogen  <response>: Ans. is a i.e., Vitamin K o Dicumarol Bishydroxycoumarin is an oral anticoagulant, which act by inhibiting the synthesis of vitamin K dependent clotting factors.Oral anticogulantso They act indirectly by interfering with the synthesis of vit K dependent clotting factors in liver,o They interfere with regeneration of the active hydroquinone form of vit K, which is required for the final step gamma carboxylating glutamate residues of prothrombin factor II andfactor VII, IX and X. This carboxylation is essential for the ability of the clotting factors to bind Ca2 and to get bound to phospholipid surface, necessary for coagulation sequence to proceed.Mechanism of actiono During g- carboxylation of the coagulant factor II, VII, IX and X in the liver, active vitamin K Vit K hydroquinone is oxidized to an epoxide vit K epoxide.o Vit K epoxide must be reduced to vit K hydroquinone to become active once again vit K cycle,o Vit K epoxide is reduced to vit K hydroquinone by vit K reductase.o This vit K reductase is inhibited by oral anticoagulants.o Factor VII has the shortest plasma t 12 6 hrs, its level falls first when warfarin is given, followed by factor IX t 12 24 hrs, factor X i 12 40 hrs and prothrombin t 12 60 hrs.o Though the synthesis of clotting factors diminishes within 2-4 hours of warfarin administration, anticoagulant effect develops gradually over the next 1-3 days as the levels of the clotting factors already present in plasma decline progressively. Thus oral anticoagulants are used for maintenance for anticoagulation for initiation heparin is used.o Protein C, protein S, osteocalcin are also inhibited because these proteins also contain glutamate residues that require vit K dependent gamma carboxylation.o Protein C and Protein S are anticoagulant factor and have a shorter t 12 than the procoagulant factors II, VII, IX X, and their more rapid decline in concentration creates a transient hvpercoagulahle state - Initiate anticoagulation with heparin until the effect of warfarin is well established.o Warfarin is the most popular oral anticoagulant.o Bishydroxycoumarin Dicumarol is the longest acting oral anticoagulant.o Ethylbiscoumacetate is the shortest acting anticoagulant.o Warfarin is rapidly and completely absorbed from intestines and is 99 plasma protein bound. Its kinetics changes from first order to zero order at higher concentrations.o For monitoring the effect of oral anticoagulant prothrombin time PT is used because they selectively inhibit the extrinsic pathway. 