Warfarin Restart Dosing After Holding for Supratherapeutic INR
Restart warfarin at approximately 9.6 mg per week (approximately 1.4 mg daily), which represents a 20% reduction from your previous weekly dose of 12 mg. 1
Rationale for Dose Reduction
Your INR of 2.9 after holding warfarin for 2 days indicates you were likely supratherapeutic (INR >3.0) before the hold, given the typical decay pattern of warfarin's anticoagulant effect. 1 The guideline-based approach for supratherapeutic INR management recommends:
- For INR 3.0-3.9: Decrease weekly warfarin dose by 10% 2
- For elderly patients or those with heightened sensitivity: Use a 15-20% reduction rather than 10% 1
Given that your INR remained at 2.9 after a 2-day hold (suggesting the pre-hold INR was likely 3.5-4.0 based on warfarin's half-life), a 20% dose reduction is most appropriate. 1
Specific Restart Instructions
- Do not restart warfarin until INR falls below 3.0 1
- Starting dose: 1.4 mg daily (or alternate 1 mg and 2 mg on different days to achieve 9.6 mg weekly) 1
- Timing: Resume warfarin the evening your INR drops below 3.0 1
Post-Restart Monitoring Schedule
Your monitoring should follow this intensive schedule to ensure stability:
- Days 1-3 after restart: Check INR daily 1
- Week 1-2: Check INR 2-3 times per week 2, 1
- Weeks 3-4: Check INR once weekly if stable 2, 1
- After 4 weeks of stability: Extend to every 1-2 months 1
Critical Pitfalls to Avoid
Do NOT administer vitamin K for an INR of 2.9 without bleeding, as this will cause warfarin resistance and potentially create a prothrombotic state when you restart. 1 The threshold for vitamin K in asymptomatic patients is INR >5.0. 1
Do NOT restart at your previous dose of 12 mg weekly (approximately 1.7 mg daily), as this will result in recurrent supratherapeutic INR. 1 Research confirms that patients restarted at their previous maintenance dose after a hold for elevated INR experience repeated INR elevations. 3
Do NOT use a loading dose strategy in your situation. While loading doses (approximately 40% above maintenance) can shorten time to therapeutic INR when restarting after elective procedures, 4, 5 they are inappropriate after a hold for supratherapeutic INR, as you need dose reduction, not escalation. 1
Investigate Underlying Causes
Before restarting, identify what caused your INR elevation:
- Medication changes: New antibiotics, NSAIDs, or other interacting drugs are the most common precipitants 1
- Intercurrent illness: Fever, diarrhea, or acute infections alter drug absorption 1
- Dietary changes: Decreased vitamin K intake 1
- Alcohol consumption: Increased alcohol impairs warfarin metabolism 1
Alternative Dosing Consideration
If you prefer simpler daily dosing rather than alternating doses, 1.5 mg daily (10.5 mg weekly) represents a more conservative 12.5% reduction and may be acceptable if you have no other risk factors for elevated INR. 2 However, the 20% reduction to 9.6 mg weekly is preferred based on the magnitude of your INR elevation. 1
Evidence Strength Note
The recommendation for 20% dose reduction comes from high-quality guidelines specifically addressing supratherapeutic INR management in the maintenance phase. 1 The FDA label supports individualized dosing adjustments based on INR response, recommending maintenance doses of 2-10 mg daily with flexibility. 6 Research on warfarin reinitiation after elective procedures 4, 5, 3 is not directly applicable to your situation, as those studies addressed patients with previously stable INRs who had warfarin held for procedures, not for supratherapeutic INR.