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Which factor could have contributed to RE’s fluctuating INR readings?

A. Inconsistent diet of vitamin K-containing foods

B. Drug interaction with multivitamin

C. Taking warfarin at different times of the day

D. Inconsistent exercise routines

Correct answer: A

Rationale: Vitamin K intake affects warfarin’s effect, so a consistent amount of vitamin K in the diet is recommended to help RE maintain therapeutic INR levels. While there could be a drug interaction between warfarin and a multivitamin that contains vitamin K, it would not cause fluctuating levels if RE takes her multivitamin daily. Since warfarin has a prolonged effect on INR, taking warfarin at different times of the day would not significantly affect RE’s INR levels. Inconsistent exercise routines will not have a significant effect on INR levels.

What is RE’s CHA2DS2-VASc score?

A. 5

B. 6

C. 7

D. 8

Correct answer: C

Rationale: RE has heart failure (1 point), hypertension (1 point), age 65–74 years (1 point), diabetes (1 point), stroke (2 points), and female gender (1 point). Anticoagulation with warfarin or a DOAC is recommended with a CHA2DS2-VASc score of 2 or more for women in the CHEST guidelines,1 and a CHA2DS2-VASc score of 3 or more for women in the ACC/AHA guidelines.1

Which antithrombotic therapy would be the best option for RE?

A. Rivaroxaban 20 mg PO daily

B. Aspirin 81 mg PO daily

C. Enoxaparin 100 mg SC bid

D. Apixaban 10 mg PO bid for 7 days, then 5 mg PO bid

Correct answer: A

Rationale: Direct oral anticoagulants (rivaroxaban, apixaban, dabigatran, and edoxaban) are recommended over warfarin for stroke prevention in patients with atrial fibrillation.1,2 Rivaroxaban has the correct dosing for RE’s renal function based on actual body weight. Aspirin is no longer recommended for stroke prevention in atrial fibrillation and enoxaparin is not used for stroke prevention as an outpatient. The dosing listed here for apixaban is for treatment of venous thromboembolism, though apixaban is commonly used for stroke prevention in atrial fibrillation due to its favorable safety and efficacy profile.


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