MTM Anticoagulation Management 3 — Questions and Answers
Question 1: A patient with acute PE is found to have antiphospholipid syndrome (APS). Which anticoagulant strategy is preferred for long-term management?
- Rivaroxaban 20 mg daily
- Apixaban 5 mg twice daily
- Warfarin with target INR 2–3 (Correct answer)
- Dabigatran 150 mg twice daily
Correct answer: Warfarin with target INR 2–3
Warfarin remains the preferred anticoagulant for APS because DOACs have been associated with higher rates of arterial thromboembolism in this population.
Question 2: When monitoring unfractionated heparin (UFH) therapy using anti-Xa levels, what is the therapeutic target range for treatment of VTE?
- 0.1–0.4 units/mL
- 0.3–0.7 units/mL
- 0.5–1.0 units/mL (Correct answer)
- 1.0–2.0 units/mL
Correct answer: 0.5–1.0 units/mL
The therapeutic anti-Xa range for UFH treatment of VTE is 0.3–0.7 units/mL (some guidelines specify 0.3–0.7 or up to 1.0 units/mL depending on the protocol).
Question 3: A 72-year-old patient with non-valvular atrial fibrillation has a CHA₂DS₂-VASc score of 2. What is the recommended anticoagulation approach?
- Antiplatelet therapy with aspirin alone
- No antithrombotic therapy is required
- Oral anticoagulation is recommended (Correct answer)
- Low-dose LMWH is preferred over oral agents
Correct answer: Oral anticoagulation is recommended
A CHA₂DS₂-VASc score ≥2 in males (or ≥3 in females) indicates high stroke risk and warrants oral anticoagulation therapy.
Question 4: Which of the following is a contraindication to the use of fondaparinux?
- History of heparin-induced thrombocytopenia (HIT)
- Obesity with BMI >40 kg/m²
- Severe renal impairment (CrCl <30 mL/min) (Correct answer)
- Concurrent use of aspirin
Correct answer: Severe renal impairment (CrCl <30 mL/min)
Fondaparinux is contraindicated in severe renal impairment (CrCl <30 mL/min) due to drug accumulation and excessive bleeding risk.
Question 5: A pharmacist reviews a patient's medication list and notes they are on warfarin plus amiodarone started 3 months ago. The INR is now 4.8. What best explains this interaction?
- Amiodarone induces CYP2C9, increasing warfarin metabolism
- Amiodarone inhibits CYP2C9 and CYP3A4, reducing warfarin clearance (Correct answer)
- Amiodarone displaces warfarin from protein binding sites acutely
- Amiodarone increases vitamin K absorption from the gut
Correct answer: Amiodarone inhibits CYP2C9 and CYP3A4, reducing warfarin clearance
Amiodarone inhibits CYP2C9 and CYP3A4, reducing warfarin metabolism; because amiodarone has a very long half-life, this interaction can persist for months after drug initiation.
Question 6: During an MTM session, a patient on dabigatran reports taking an over-the-counter proton pump inhibitor. What counseling point is most relevant?
- PPIs increase dabigatran levels and worsen GI bleeding risk
- PPIs reduce dabigatran bioavailability by increasing gastric pH (Correct answer)
- The combination is absolutely contraindicated
- PPIs have no interaction with dabigatran
Correct answer: PPIs reduce dabigatran bioavailability by increasing gastric pH
Dabigatran is formulated as a prodrug requiring an acidic gastric environment; PPIs raise gastric pH and reduce dabigatran bioavailability by approximately 12–30%.
Question 7: A patient with provoked DVT (post-surgical) completes 3 months of anticoagulation with no residual risk factors. What is the recommended duration of therapy?
- Continue indefinitely on reduced-dose DOAC
- 6 months of therapy is always required
- 3 months is sufficient; discontinue anticoagulation (Correct answer)
- Antiplatelet therapy should be started upon stopping anticoagulants
Correct answer: 3 months is sufficient; discontinue anticoagulation
For provoked VTE with a transient reversible risk factor, 3 months of anticoagulation is adequate and indefinite therapy is not recommended.
MTM Anticoagulation Management 3
A patient with acute PE is found to have antiphospholipid syndrome (APS).
Which anticoagulant strategy is preferred for long-term management?