BCACP Anticoagulation Management 1 — Questions and Answers
Question 1: What is the target INR range for a patient with nonvalvular atrial fibrillation on warfarin?
- 1.5–2.0
- 2.0–3.0 (Correct answer)
- 2.5–3.5
- 3.0–4.0
Correct answer: 2.0–3.0
The standard therapeutic INR range for nonvalvular atrial fibrillation is 2.0–3.0 to balance stroke prevention with bleeding risk.
Question 2: Which of the following clotting factors is NOT inhibited by warfarin?
- Factor II (Thrombin)
- Factor VII
- Factor VIII (Correct answer)
- Factor X
Correct answer: Factor VIII
Warfarin inhibits only vitamin K-dependent clotting factors (II, VII, IX, X); Factor VIII is not vitamin K-dependent and is therefore unaffected.
Question 3: A patient on warfarin for atrial fibrillation presents with an INR of 8.5 and no signs of active bleeding. What is the most appropriate management?
- Continue warfarin at current dose and recheck INR in one week
- Hold warfarin, administer oral vitamin K 2.5 mg, and recheck INR in 24–48 hours (Correct answer)
- Administer IV vitamin K 10 mg and fresh frozen plasma immediately
- Discontinue warfarin permanently and switch to a DOAC
Correct answer: Hold warfarin, administer oral vitamin K 2.5 mg, and recheck INR in 24–48 hours
CHEST guidelines recommend holding warfarin and administering low-dose oral vitamin K (2.5 mg) for INR above 5 without active bleeding to safely lower the INR.
Question 4: Which drug is most likely to INCREASE warfarin's anticoagulant effect by inhibiting its primary metabolizing enzyme?
- Rifampin
- Carbamazepine
- Fluconazole (Correct answer)
- St. John's Wort
Correct answer: Fluconazole
Fluconazole is a strong CYP2C9 inhibitor, the primary enzyme responsible for warfarin (S-enantiomer) metabolism, leading to increased warfarin levels and elevated INR.
Question 5: A patient with a bileaflet mechanical mitral valve requires long-term anticoagulation. Which agent is most appropriate?
- Rivaroxaban 20 mg daily
- Apixaban 5 mg twice daily
- Dabigatran 150 mg twice daily
- Warfarin with target INR 2.5–3.5 (Correct answer)
Correct answer: Warfarin with target INR 2.5–3.5
Warfarin is the only anticoagulant approved for mechanical heart valves; all DOACs are contraindicated due to demonstrated increased risk of thromboembolic events in this population.
Question 6: What is the correct target INR range for a patient with a bileaflet mechanical aortic valve and no additional thromboembolic risk factors?
- 1.5–2.0
- 2.0–3.0 (Correct answer)
- 2.5–3.5
- 3.5–4.5
Correct answer: 2.0–3.0
A bileaflet mechanical aortic valve without additional risk factors targets INR 2.0–3.0; higher-risk situations (mitral position, prior thromboembolism) require 2.5–3.5.
Question 7: Which is a guideline-recommended first-line option for initial treatment of acute DVT in a patient with adequate renal function and no active cancer?
- Warfarin 5 mg daily alone without heparin bridging
- Rivaroxaban 15 mg twice daily for 21 days, then 20 mg daily (Correct answer)
- Aspirin 325 mg daily for 3 months
- Unfractionated heparin alone without transition to an oral agent
Correct answer: Rivaroxaban 15 mg twice daily for 21 days, then 20 mg daily
Rivaroxaban monotherapy using a dual-dose regimen (15 mg BID x21 days, then 20 mg daily) is guideline-recommended for acute DVT without requiring initial parenteral therapy.
BCACP Anticoagulation Management 1
What is the target INR range for a patient with nonvalvular atrial fibrillation on warfarin?