Management of INR 5.28 on Warfarin
For a patient with INR 5.28 without active bleeding, immediately withhold warfarin for 1-2 doses and administer oral vitamin K 1-2.5 mg if the patient has increased bleeding risk factors (advanced age >65 years, history of bleeding, concomitant antiplatelet drugs, renal failure, or alcohol use); otherwise, simply withhold warfarin and monitor closely. 1, 2, 3
Immediate Management Algorithm
Withhold warfarin completely until INR falls back into therapeutic range, which typically occurs within 24-72 hours in most patients. 1, 3
Vitamin K Decision Point
The decision to add vitamin K depends on bleeding risk stratification:
- High-risk patients (age >65-75 years, history of bleeding, concomitant antiplatelet therapy, renal failure, alcohol use): Administer oral vitamin K 1-2.5 mg 1, 2, 3
- Low-risk patients without these factors: Vitamin K is NOT routinely required—simply withhold warfarin and monitor 1, 3
Oral vitamin K is the preferred route for non-emergency situations due to predictable effectiveness (95% of patients show INR reduction within 24 hours, with 85% achieving INR <4.0), convenience, and safety compared to parenteral routes. 3, 4
Critical Monitoring Requirements
Recheck INR within 24-48 hours after intervention to confirm appropriate reduction, then continue monitoring every 24-48 hours until INR stabilizes in therapeutic range. 2, 3
Restarting Warfarin
When INR falls below 3.5 or back into therapeutic range:
- Reduce the weekly warfarin dose by 20-30% from the previous dose to prevent recurrence of supratherapeutic INR 1, 2
- For example, if previously on 10 mg daily, restart at 8 mg daily (20% reduction) 2
Essential Investigation
Identify and correct the cause of INR elevation before resuming therapy, including: 2, 3
- New medications or drug interactions
- Dietary changes in vitamin K intake
- Medication non-adherence
- Acute illness or infection
- Changes in liver or renal function
- Alcohol consumption changes
- Weight changes
Critical Pitfalls to Avoid
Never administer high-dose vitamin K (≥10 mg) for this INR level, as it creates warfarin resistance for up to a week and makes re-anticoagulation extremely difficult. 1, 2, 3
Do not use IV vitamin K unless active bleeding is present, due to the risk of anaphylactoid reactions (3 per 100,000 doses) that can result in cardiac arrest. 1
Do not restart warfarin at the original dose without dose reduction—this will likely result in recurrent supratherapeutic INR. 2
Risk Context
While the absolute daily risk of bleeding at INR 5.28 remains relatively low (<5.5 per 1000 per day), the risk increases exponentially above INR 5.0 and becomes clinically significant. 1, 4, 5 Elderly patients have amplified bleeding risk at any given INR level, making age a critical factor in management decisions. 1, 3
When to Escalate Management
If active bleeding develops at any point, immediately escalate to:
- 5-10 mg IV vitamin K by slow infusion over 30 minutes PLUS
- 4-factor prothrombin complex concentrate (PCC) 50 U/kg IV for rapid reversal (achieves INR correction within 5-15 minutes) 1
However, for INR 5.28 without bleeding, aggressive reversal with PCC is not indicated and exposes the patient to unnecessary thrombotic risk. 1