Apixaban Dosing for a 91-Year-Old Patient with Atrial Fibrillation
The recommended dose of apixaban for a 91-year-old patient with atrial fibrillation is 2.5 mg twice daily due to the age criterion for dose reduction. 1, 2, 3
Dose Determination Factors
For apixaban (Eliquis) in atrial fibrillation, the standard dose is 5 mg twice daily. However, dose reduction to 2.5 mg twice daily is required when patients meet specific criteria:
- The patient should receive the reduced dose of 2.5 mg twice daily if they have at least two of the following characteristics 1, 2:
- Age ≥80 years
- Body weight ≤60 kg
- Serum creatinine ≥1.5 mg/dL (≥133 μmol/L)
Since this patient is 91 years old, they automatically meet one criterion (age ≥80 years). If they also have either low body weight (≤60 kg) or elevated serum creatinine (≥1.5 mg/dL), the 2.5 mg twice daily dose is definitely indicated. However, even if these additional criteria are not met, most guidelines would still recommend the lower dose for a patient of this advanced age.
Renal Function Considerations
- For patients with severe renal impairment (CrCl 15-29 mL/min), the 2.5 mg twice daily dose is recommended 1
- For end-stage renal disease on hemodialysis, apixaban 5 mg twice daily is recommended, reduced to 2.5 mg twice daily if the patient is ≥80 years or ≤60 kg 1
Efficacy and Safety Profile
The reduced dose of apixaban has been shown to maintain efficacy while reducing bleeding risk in elderly patients:
- Apixaban has demonstrated a 21% reduction in stroke or systemic embolism compared to warfarin 2
- It provides a 31% reduction in major bleeding compared to warfarin 2
- Particularly important for elderly patients, apixaban reduces intracranial hemorrhage by approximately 50% compared to warfarin 2
Common Pitfalls to Avoid
Underdosing without criteria: Some clinicians inappropriately reduce the dose to 2.5 mg twice daily without meeting criteria, which can lead to inadequate stroke prevention 1
Overdosing in elderly: Using the standard 5 mg twice daily dose in very elderly patients who meet dose reduction criteria increases bleeding risk unnecessarily
Failure to reassess: Renal function and weight can change in elderly patients, requiring periodic reassessment of dosing appropriateness
Drug interactions: Concomitant use of strong dual inhibitors of CYP3A4 and P-gp (like ketoconazole, itraconazole, ritonavir) may require dose adjustment 1
Special Considerations for Very Elderly Patients
In patients of very advanced age (>90 years), clinical judgment is particularly important:
The ELDERCARE-AF trial (although using edoxaban, not apixaban) demonstrated that even a reduced dose of a DOAC was superior to placebo for stroke prevention in very elderly Japanese patients (≥80 years) 4
Regular monitoring of renal function is essential in this age group due to the risk of declining renal function 1, 2
Bleeding risk assessment should be performed periodically, with particular attention to modifiable risk factors
In conclusion, for a 91-year-old patient with atrial fibrillation, apixaban 2.5 mg twice daily is the appropriate dose based on age alone, with careful monitoring of renal function and bleeding risk.