An 85 year old female (5’7”, 54 kg) presents to your ambulatory clinic for management of newly diagnosed atrial fibrillation. Her physician referred this patient to you to assess which direct oral anticoagulant (DOAC) be most appropriate for the patient for stroke prevention. Her past medical history includes hypertension, diabetes, and depression. She is currently taking metformin 1g BID, lisinopril/HCTZ 40/12.5mg daily, and sertraline 100mg daily.  Lab values from her most recent basic metabolic panel (BMP) drawn one week ago are listed below:

Sodium: 134 mEq/L

Potassium: 4.2 mEq/L

Chloride: 103 mmol/L

Calcium: 9.8 mg/dL

CO2: 24 mmol/L

BUN: 12 mg/dL

SCr: 1.1 mg/dL

Glucose: 128 mg/dL

Which of the following would be the most appropriate recommendation to the physician?

A. Apixaban 5 mg BID

B. Apixaban 2.5 mg BID

C. Rivaroxaban 20 mg daily

D. Anticoagulation is not indicated in this patient

Answer with rationale:

The correct answer is B.

Atrial fibrillation is a type of arrhythmia in which the atria beat irregularly, causing altered blood flow into the ventricles. This can cause pooling of blood in the atria which may lead to a clot, which is why anticoagulation is important for stroke prevention in these patients. A CHA2DS2–VASc Score is commonly used to assess risk of ischemic stroke in patients with atrial fibrillation, which guides decision making for whether or not a patient is indicated for anticoagulation. Scores of 2 or greater in males and 3 or greater in females favor anticoagulation with a DOAC over a vitamin K antagonist when possible (CHEST guidelines). Our patient has a CHA2DS2-VASc score of 5 (+1 hypertension, +2 age ≥ 75 years, +1 diabetes, +1 female), which categorizes this patient as “high risk” for ischemic stroke. Therefore, she is indicated for anticoagulation which makes answer D incorrect.

Apixaban (Eliquis) is a factor Xa inhibitor with an FDA indication for stroke prevention in patients with nonvalvular atrial fibrillation. For this indication, apixaban is dosed 5 mg twice daily. However, if the patient has any 2 of the following: age ≥ 80 years, body weight ≤ 60 kg, or SCr ≥1.5 mg/dL, then the dose should be reduced to 2.5 mg twice daily. This patient meets 2 criteria with age ≥ 80 years and body weight ≤ 60 kg, making answer B correct.

Rivaroxaban (Xarelto) is also a factor Xa inhibitor with an FDA indication for stroke prevention in patients with nonvalvular atrial fibrillation. The normal dose is 20 mg daily with an evening meal. For patients with CrCl 15-50 mL/min, the dose of rivaroxaban should be renally adjusted to 15 mg daily with an evening meal. Rivaroxaban should be avoided in patients with CrCl <15 mL/min.  For doses ≥ 15 mg, food should be administered to increase bioavailability of the drug. Using the Cockcroft-Gault equation, this patient has a CrCl of 31.9 mL/min, making answer C incorrect.