All about warfarin are true EXCEPT?: (A) Half-life is 36 hours, (B) Crosses placenta, (C) Contraindicated in hepatic failure, (D) Inhibits all vitamin K dependent clotting factors
Answer is C. Ans. is 'c' i.e., Contraindicated in hepatic failure o Liver disease requires dose reduction, but is not a contraindication. Effect of liver disease on warfarin o In liver diseases the dose of oral anticoagulats needs to be decreased because in liver disease the hepatic synthesis of clotting factors is reduced. o Thus there is already a deficiency of clotting factors (i.e. there is preexisting anticoagulant state). o Administration of warfarin is this state increases the risk of bleeding. About other options o Warfarin is an indirectly acting anticoagulant, i.e. it inhibits vitamin K which in turn inhibits coagulation factors. o T1/2 of warfarin is 36 hrs. o Warfarin can cross placenta and cause fetal warfarin syndrome. Therefore it is contraindicated pregnancy. Patient is switched to heparin from warfarin during pregnancy.