MTM Anticoagulation Management 5 — Questions and Answers
Question 1: A patient on warfarin therapy has a time in therapeutic range (TTR) of 42% over the past 6 months. What is the most appropriate next step?
- Switch to aspirin to reduce bleeding risk
- Investigate causes of poor INR control before considering a DOAC switch (Correct answer)
- Increase warfarin dose by 20% and recheck in 4 weeks
- Refer the patient for surgical left atrial appendage closure
Correct answer: Investigate causes of poor INR control before considering a DOAC switch
Before switching to a DOAC, clinicians should assess the causes of low TTR (diet, adherence, drug interactions) as some causes are correctable, though a DOAC may ultimately be preferred.
Question 2: Which anticoagulant is preferred for the treatment of cancer-associated thrombosis based on current guidelines?
- Warfarin with target INR 2.5–3.5
- Low molecular weight heparin or edoxaban/rivaroxaban (DOACs) (Correct answer)
- Unfractionated heparin infusion for the duration of chemotherapy
- Fondaparinux subcutaneously for 6 months
Correct answer: Low molecular weight heparin or edoxaban/rivaroxaban (DOACs)
LMWH has historically been preferred for cancer-associated thrombosis, but DOACs (edoxaban, rivaroxaban) are now guideline-endorsed alternatives except in patients with GI malignancies at high bleeding risk.
Question 3: A patient taking warfarin for a mechanical aortic valve reports consistently eating large amounts of spinach and kale. What dietary counseling should be provided?
- Eliminate all green vegetables immediately
- Maintain a consistent daily intake of vitamin K-rich foods rather than avoiding them (Correct answer)
- Switch to low-vitamin K protein-based diet exclusively
- Take supplemental vitamin K to counterbalance the dietary intake
Correct answer: Maintain a consistent daily intake of vitamin K-rich foods rather than avoiding them
Patients on warfarin should be counseled to maintain consistent (not eliminate) vitamin K intake, as sudden increases or decreases alter INR unpredictably.
Question 4: A patient with PE has a submassive (intermediate-risk) PE with right heart strain on echo. They are hemodynamically stable. What is the initial anticoagulation of choice?
- Catheter-directed thrombolysis immediately
- Systemic thrombolysis with alteplase
- Anticoagulation with LMWH or DOAC and close monitoring (Correct answer)
- Surgical embolectomy
Correct answer: Anticoagulation with LMWH or DOAC and close monitoring
For submassive PE with hemodynamic stability, anticoagulation alone is the recommended initial therapy, with systemic thrombolysis reserved for clinical deterioration.
Question 5: A pharmacist is managing an anticoagulation clinic and receives labs for a patient on warfarin who also started taking naproxen OTC. Which concern is most clinically relevant?
- Naproxen induces warfarin metabolism and will lower the INR
- Naproxen can displace warfarin from protein binding and inhibit platelet function, increasing bleeding risk (Correct answer)
- Naproxen reduces GI absorption of warfarin, requiring a dose increase
- NSAIDs have no clinically significant interaction with warfarin
Correct answer: Naproxen can displace warfarin from protein binding and inhibit platelet function, increasing bleeding risk
NSAIDs like naproxen inhibit platelet aggregation and can displace warfarin from albumin, compounding bleeding risk even if the INR does not markedly change.
Question 6: Which score is used to estimate the pretest probability of HIT before ordering confirmatory laboratory testing?
- HAS-BLED score
- 4T score (Correct answer)
- CHADS₂ score
- HEMORR₂HAGES score
Correct answer: 4T score
The 4T score (Thrombocytopenia, Timing, Thrombosis, oTher causes) estimates pretest probability of HIT and guides decisions about ordering anti-PF4 antibody testing.
Question 7: A patient on edoxaban 60 mg daily for AF is newly prescribed rifampin for latent TB. What is the most appropriate management?
- Reduce edoxaban to 30 mg daily to compensate for the interaction
- Switch to warfarin with close INR monitoring, as rifampin is a strong inducer of edoxaban metabolism (Correct answer)
- Continue edoxaban 60 mg daily with no adjustment needed
- Add aspirin to maintain adequate stroke prevention
Correct answer: Switch to warfarin with close INR monitoring, as rifampin is a strong inducer of edoxaban metabolism
Rifampin is a potent inducer of P-glycoprotein and CYP3A4, significantly reducing edoxaban (and other DOAC) exposure; warfarin with frequent INR monitoring is preferred in this scenario.
MTM Anticoagulation Management 5
A patient on warfarin therapy has a time in therapeutic range (TTR) of 42% over the past 6 months.
What is the most appropriate next step?