Apixaban 2.5 mg PO every 12 hours (Option D)
For this 82-year-old patient weighing 58 kg with a CrCl of 45 mL/min, apixaban 2.5 mg twice daily is the most appropriate recommendation because he meets at least two of the three dose-reduction criteria: age ≥80 years and weight ≤60 kg. 1, 2
Dose-Reduction Criteria for Apixaban
The FDA prescribing information and AHA/ACC/HRS guidelines clearly specify that apixaban should be reduced to 2.5 mg twice daily when at least 2 of the following 3 characteristics are present 1, 2:
- Age ≥80 years
- Body weight ≤60 kg
- Serum creatinine ≥1.5 mg/dL
This patient meets two criteria:
- Age: 82 years (≥80 years) ✓
- Weight: 58 kg (≤60 kg) ✓
- Renal function: CrCl 45 mL/min (moderate impairment, but serum creatinine value not provided)
Why Not the Other Options
Option A (Rivaroxaban 20 mg daily): This is incorrect because rivaroxaban requires dose reduction to 15 mg daily when CrCl is 30-50 mL/min 1. The 20 mg dose is only appropriate for CrCl >50 mL/min.
Option B (Apixaban 5 mg twice daily): This is the standard dose but inappropriate here because the patient meets two dose-reduction criteria (age and weight) 1, 3, 2.
Option C (Rivaroxaban 10 mg daily): This dose does not exist for stroke prevention in atrial fibrillation. The approved doses are 20 mg daily (CrCl >50 mL/min) or 15 mg daily (CrCl 30-50 mL/min) 1.
Renal Function Considerations
With a CrCl of 45 mL/min, this patient has moderate renal impairment 1. The 2014 AHA/ACC/HRS guidelines specifically recommend apixaban 5 mg or 2.5 mg twice daily for patients with CrCl 30-50 mL/min, with the dose determined by the presence of additional criteria 1. Since this patient meets two additional criteria beyond renal function alone, the 2.5 mg dose is mandated 1, 2.
Apixaban Advantages in This Population
Apixaban is particularly suitable for elderly patients with renal impairment because 4:
- Lower renal clearance (25%) compared to dabigatran (80%) or edoxaban (50%)
- Proven efficacy and safety across all age groups in clinical trials 3
- No dose adjustment needed based solely on moderate renal impairment when other criteria are absent 1, 2
Critical Monitoring Requirements
Renal function must be reassessed 1:
- At least annually in stable patients
- Every 2-3 times per year in patients with moderate renal impairment (CrCl 30-49 mL/min)
- More frequently if clinical deterioration occurs 5
This is particularly important because studies show that 29-44% of patients with atrial fibrillation and heart failure require anticoagulant dose adjustments during follow-up due to fluctuating renal function 5.
Common Pitfall to Avoid
Do not use serum creatinine alone to assess renal function. The guidelines explicitly require calculation of CrCl using the Cockcroft-Gault equation 1. In elderly patients with low body weight, serum creatinine may appear normal despite significantly reduced CrCl 1.