Special Populations>Monitoring Priority Practice Test

A 79-year-old man with nonvalvular atrial fibrillation is initiated on warfarin 5 mg nightly after declining a direct oral anticoagulant due to cost. Baseline laboratory values are: INR 1.0, aPTT 29 seconds, hemoglobin 13.8 g/dL, platelets 210,000/mm3, AST 22 U/L, ALT 18 U/L, and serum creatinine 1.0 mg/dL (estimated eGFR 72 mL/min/1.73 m2). He has no history of liver disease or bleeding. Current medications include lisinopril, atorvastatin, and acetaminophen as needed; he does not take antiplatelet agents or NSAIDs. He eats salads with spinach several times per week and has been counseled to keep his vitamin K intake consistent. The provider plans to adjust the dose over the next several weeks with close follow-up.

A 78-year-old man with nonvalvular atrial fibrillation is initiated on warfarin 5 mg daily for stroke prevention. He has hypertension and osteoarthritis. Baseline labs: INR 1.0, hemoglobin 13.5 g/dL, platelets 220,000/mm3, AST 22 U/L, ALT 24 U/L, albumin 3.8 g/dL, serum creatinine 0.9 mg/dL (eGFR 70 mL/min/1.73 m2). Medications include lisinopril, hydrochlorothiazide, and acetaminophen as needed. He drinks one glass of wine per week and denies herbal supplements. Blood pressure is 128/72 mm Hg and heart rate is 78 bpm. He is instructed on dietary vitamin K consistency and drug interaction risks. The prescriber plans to adjust the dose based on response and safety over the next several weeks.