Which of the following drugs should not be administered concomitantly with warfarin as it decreases the effect of oral anticoagulants: (A) Broad spectrum antibiotic, (B) Cimetidine, (C) Aspirin, (D) Oral contraceptive
Answer is D. Oral contraceptives Estrogen increases the synthesis of various clotting factors and produce a hypercoagulable state. Thus OCP containing estrogen decrease the effectiveness of warfarin and other oral anticoagulants.