Dicumarol is a drug that impairs the utilization of vitamin K by the liver. Dicumarol therapy, therefore, would decrease the plasma concentration of which of the following procoagulants?: (A) Prothrombin, (B) Fibrinogen, (C) Factor XI, (D) Ac-globulin (factor V)
Answer is A. Dicumarol inhibits the action of vitamin K, which is a necessary cofactor for the enzyme that catalyzes the conversion of glutamic acid residues to g-carboxyglutamic acid residues.Six of the proteins involved in clotting require conversion of a number of glutamic acid residues to g-carboxyglutamic acid residues before being released into the circulation, and hence all six are vitamin K-dependent. These proteins include factors II (prothrombin)Others are; factors VII, IX, and X, protein C, and protein S Ref: Ganong's Review of Medical Physiology Twenty-Third Edition Page No: 535