NAPLEX Question of the Week: Anticoagulation

Anticoagulation is involved in different disease states associated with clotting (e.g. venous thromboembolism (VTE), atrial fibrillation (a fib), and clotting disorders) in both the inpatient and outpatient setting. There are specific dosing regimens to know as a pharmacist based on indication.

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AB is a 59-year old male, weighing 81 kg, with a SCr of 1.2 mg/dL. He presents to your pharmacy today with a new prescription for a blood thinner. Upon further questioning, you find out that the patient was just discharged from the hospital and recently diagnosed with atrial fibrillation and has a CHADS2-VASC score of 3.  His PMH includes HFrEF, DM, HTN, dyslipidemia, gout, GERD, and now atrial fibrillation. He is currently taking lisinopril 40mg daily, metformin 1g BID, atorvastatin 40mg daily, allopurinol 300mg daily, pantoprazole 40mg daily, and carvedilol 12.5mg BID. Which of the following agents would be a correct choice for AB?

a. Dabigatran 150mg orally daily

b. Lovenox 40 mg subcutaneous daily

c. Rivaroxaban 15 mg PO BID x 21 days, then 20 mg daily

d. Apixaban 5 mg PO BID

e. Aspirin 81mg PO daily

Answer with Rationale:

Answer: d - apixaban 5 mg PO BID is the appropriate dosing for atrial fibrillation.

Additionally, a unique pearl regarding apixaban dosing is the following. Apixaban should be dose reduced to 2.5 mg BID if the patient has 2 of the following: age 80 years old or older, weight 60 kg or less, and/or SCr 1.5 mg/dL or greater. This patient does not meet any of these, thus the normal atrial fibrillation dosing for apixaban is correct. NOTE: These dosage adjustments do not apply when using apixaban for VTE treatment as everyone should receive 10mg BID for 7 days followed by 5mg BID.

Answer a is incorrect because dabigatran is typically dosed 150mg by mouth twice daily. Answer b is wrong because this represents VTE prophylaxis dosing for lovenox not treatment dosing. Answer c is incorrect because this represents rivaroxaban dosing for VTE treatment. The correct dosing for atrial fibrillation is rivaroxaban 20 mg PO daily unless you have to renally dose adjust. Administration pearl: Rivaroxaban at the 20mg daily dose should be given with evening meal to maximize bioavailability. Answer e is incorrect as this patient's CHADS2-VASC score of 3 warrants anticoagulation, not aspirin therapy alone.

Christopher M. Bland

Clinical Professor, University of Georgia College of Pharmacy

Dr. Christopher M. Bland is a Clinical Professor at the University of Georgia College of Pharmacy at the Southeast GA campus in Savannah, GA. Dr. Bland has over 20 years of academic and clinical experience in a number of clinical areas. He is a Fellow of both the Infectious Diseases Society of America as well as the American College of Clinical Pharmacy. He is co-founder of the Southeastern Research Group Endeavor, SERGE-45, with over 80 practitioners across 14 states involved. Dr. Bland serves as Associate Editor for the NAPLEX Review Guide 4th edition as well as Editor-In-Chief for the Question of the Week. He has provided live, interactive reviews for more than 10 Colleges/Schools of Pharmacy over the course of his career.