Posted: July 24th, 2017

Warfarin is administered to a 56-year-old man following placement of a prosthetic cardiac valve. The warfarin dosage is adjusted to maintain an INR of 2.5. Subsequently, trimethoprim-sulfamethoxazole therapy is begun for a recurring urinary tract infection. In addition to monitoring prothrombin time, which of the following actions should the physician take to maintain adequate anticoagulation?

Warfarin is administered to a 56-year-old man
following placement of a prosthetic cardiac
valve. The warfarin dosage is adjusted to
maintain an INR of 2.5. Subsequently,
trimethoprim-sulfamethoxazole therapy is begun
for a recurring urinary tract infection. In addition
to monitoring prothrombin time, which of the
following actions should the physician take to
maintain adequate anticoagulation?
(A) Begin therapy with vitamin K
(B) Increase the dosage of warfarin
(C) Make no alterations in the dosage of
warfarin
(D) Decrease the dosage of warfarin
(E) Stop the warfarin and change to lowdose
aspirin