American Society Of Hematology (ASH) ITE Practice Test

Elimination of warfarin occurs primarily through which organ?

Liver—requires synthesis of new proteins without carboxylation Kidney—excretion via urine Lungs—metabolized in alveoli Spleen—phagocytosis by macrophages

Correct Answer:

Liver—requires synthesis of new proteins without carboxylation

Explanation:

Warfarin is cleared mostly by the liver. The liver metabolizes warfarin through hepatic cytochrome P450 enzymes into inactive metabolites that are then eliminated, with the drug’s effect arising from its action in the liver itself. Warfarin blocks vitamin K–dependent gamma-carboxylation of clotting factors produced in the liver, so the factors that are made are not properly carboxylated and remain inactive. Because the primary processing and clearance of warfarin occur in the liver, it is the major organ responsible for elimination. The kidneys, lungs, and spleen are not the main routes of warfarin metabolism or clearance.

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