Switching from Warfarin to Apixaban in Atrial Fibrillation with eGFR 56
Discontinue warfarin and start apixaban 5 mg twice daily when the INR falls below 2.0. 1
Transition Protocol
Stop warfarin immediately and monitor INR:
- Check INR daily or every other day after stopping warfarin 1
- Once INR drops below 2.0, initiate apixaban at the first scheduled dose 1
- Do not use bridging anticoagulation during this transition period 1
Apixaban Dosing for This Patient
With an eGFR of 56 mL/min, start apixaban 5 mg orally twice daily unless the patient meets at least 2 of the following dose-reduction criteria: 1, 2
- Age ≥80 years
- Body weight ≤60 kg
- Serum creatinine ≥1.5 mg/dL
If 2 or more criteria are met, reduce the dose to 2.5 mg twice daily. 1, 2, 3
Rationale for Standard Dosing at eGFR 56
- No dose adjustment is needed for creatinine clearance >30 mL/min based on renal function alone 3
- Apixaban has the lowest renal clearance (27%) among all direct oral anticoagulants, making it particularly suitable for patients with moderate renal impairment 4, 3
- The 2019 AHA/ACC/HRS guidelines recommend standard 5 mg twice daily dosing for moderate renal impairment (CrCl 30-50 mL/min) unless additional dose-reduction criteria are present 2, 3
Clinical Advantages of This Switch
Apixaban is superior to warfarin in patients with this level of renal function:
- NOACs are recommended over warfarin in NOAC-eligible patients with atrial fibrillation 2
- Apixaban reduces intracranial bleeding compared to warfarin across all levels of kidney function 2
- In patients with eGFR <30 mL/min, apixaban reduced stroke/systemic embolism risk by 37% compared to warfarin 5
- Real-world data show apixaban causes significantly less major bleeding than warfarin in chronic kidney disease patients 6
Monitoring Requirements
Reassess renal function regularly after initiating apixaban:
- Check renal function at least annually in stable patients 2, 3
- Monitor more frequently (every 3-6 months) if renal function is declining or unstable 3
- Use Cockcroft-Gault equation for creatinine clearance calculations, as this was used in pivotal trials 3
Critical Drug Interactions to Avoid
Do not combine apixaban with dual P-glycoprotein and strong CYP3A4 inhibitors at standard doses: 1
- If patient is taking ketoconazole, itraconazole, or ritonavir, reduce apixaban dose by 50% (from 5 mg to 2.5 mg twice daily) 1
- If already on 2.5 mg twice daily, avoid these medications entirely 1
- Avoid concomitant antiplatelet therapy (including aspirin) unless absolutely necessary, as this substantially increases bleeding risk 4
Common Pitfalls to Avoid
Do not start apixaban while INR is still elevated:
- Warfarin affects INR measurements, making them unreliable during the transition 1
- Starting apixaban with INR >2.0 increases bleeding risk due to overlapping anticoagulation 1
Do not automatically reduce the dose based solely on age or renal function:
- Age ≥80 years alone does not warrant dose reduction—need at least 2 criteria 1, 2
- eGFR 56 mL/min alone does not require dose adjustment 3
Do not use bridging anticoagulation:
- The FDA label explicitly states to start apixaban when the next warfarin dose would have been due, once INR <2.0 1
- Bridging with heparin or LMWH is unnecessary and increases bleeding risk 1
If Renal Function Declines Further
If eGFR falls to 25-30 mL/min in the future:
- Continue apixaban 5 mg twice daily (or 2.5 mg if dose-reduction criteria met) 6
- Apixaban demonstrated superior safety compared to warfarin even at CrCl 25-30 mL/min, with less major bleeding 6
- Recent evidence shows apixaban exposure remains within safe ranges at this level of renal function 6
If patient progresses to dialysis:
- Consider continuing apixaban 5 mg twice daily for stable hemodialysis patients 4
- Reduce to 2.5 mg twice daily if age ≥80 years OR weight ≤60 kg 4
- Observational data show standard-dose apixaban (5 mg) had lower stroke/embolism and death rates compared to reduced-dose and warfarin in dialysis patients 4