BCACP Anticoagulation Management 5 — Questions and Answers
Question 1: A patient on warfarin has a new prescription for fluconazole for a vaginal infection. What is the expected interaction?
- Fluconazole decreases warfarin effect by inducing CYP2C9
- Fluconazole increases warfarin effect by inhibiting CYP2C9 (Correct answer)
- No clinically significant interaction exists
- Fluconazole decreases warfarin absorption
Correct answer: Fluconazole increases warfarin effect by inhibiting CYP2C9
Fluconazole is a potent CYP2C9 inhibitor, reducing warfarin metabolism and significantly increasing INR.
Question 2: When using the HAS-BLED score in a patient with atrial fibrillation, what does a score of ≥3 indicate?
- Anticoagulation is absolutely contraindicated
- High risk of stroke without anticoagulation
- High risk of bleeding, warrants caution and closer monitoring (Correct answer)
- DOAC is preferred over warfarin
Correct answer: High risk of bleeding, warrants caution and closer monitoring
HAS-BLED ≥3 indicates high bleeding risk, prompting caution and more frequent monitoring, but is not a contraindication to anticoagulation.
Question 3: A patient with a mechanical mitral valve requires anticoagulation. Which regimen is most appropriate?
- Apixaban 5 mg twice daily
- Warfarin with a target INR of 2.5–3.5 (Correct answer)
- Warfarin with a target INR of 2.0–3.0
- Dabigatran 150 mg twice daily
Correct answer: Warfarin with a target INR of 2.5–3.5
Mechanical mitral valves require warfarin with a higher INR target of 2.5–3.5; DOACs are contraindicated for mechanical valves.
Question 4: A patient receives idarucizumab for dabigatran reversal. Which statement is correct?
- Idarucizumab reverses all DOACs nonselectively
- Idarucizumab is a specific reversal agent for dabigatran (Correct answer)
- Idarucizumab requires renal dose adjustment
- Idarucizumab takes 24 hours to achieve full reversal
Correct answer: Idarucizumab is a specific reversal agent for dabigatran
Idarucizumab (Praxbind) is a humanized monoclonal antibody fragment that specifically and rapidly reverses dabigatran's anticoagulant effect.
Question 5: A patient with antiphospholipid syndrome (APS) and recurrent DVT is on a DOAC. What change should be made?
- Continue DOAC and add aspirin
- Switch to warfarin with target INR 2.0–3.0 (Correct answer)
- Increase DOAC dose to maximum approved dose
- Add LMWH bridging indefinitely
Correct answer: Switch to warfarin with target INR 2.0–3.0
Guidelines recommend warfarin over DOACs for triple-positive APS due to higher rates of recurrent thrombosis seen with DOACs in clinical trials.
Question 6: A patient starting warfarin therapy has a CYP2C9 *2/*3 genotype. What clinical implication does this have?
- Patient will require higher than average warfarin doses
- Patient will require lower than average warfarin doses due to reduced enzyme activity (Correct answer)
- No dose adjustment needed as genotype doesn't affect warfarin
- Patient should receive a DOAC instead
Correct answer: Patient will require lower than average warfarin doses due to reduced enzyme activity
CYP2C9 *2 and *3 alleles encode enzymes with reduced activity, leading to decreased warfarin metabolism and lower dose requirements.
Question 7: A patient on apixaban 5 mg twice daily for atrial fibrillation develops end-stage renal disease requiring hemodialysis. What is the most appropriate action?
- Continue apixaban 5 mg twice daily (Correct answer)
- Reduce apixaban to 2.5 mg twice daily
- Switch to warfarin with target INR 2.0–3.0
- Discontinue all anticoagulation
Correct answer: Continue apixaban 5 mg twice daily
Apixaban is now FDA-approved for use in ESKD patients on dialysis at the standard 5 mg twice daily dose based on pharmacokinetic data and clinical studies.
BCACP Anticoagulation Management 5
A patient on warfarin has a new prescription for fluconazole for a vaginal infection.
What is the expected interaction?