What adjustment should be made to a patient's Coumadin (warfarin) regimen, currently 3 mg on Sundays and 5 mg on weekdays, with an International Normalized Ratio (INR) of 3.2, slightly above the target range of 2-3?

Warfarin Dose Adjustment for INR 3.2

For a patient with INR 3.2 (target 2-3) on 3 mg Sunday and 5 mg other days (31 mg/week), withhold warfarin for 1 dose, then reduce the weekly dose by 10-15% to approximately 27-28 mg/week—practically achieved by taking 3 mg on Sunday and Thursday, with 5 mg on the remaining 5 days. 1, 2

Rationale for Dose Reduction

• The INR of 3.2 is minimally supratherapeutic and does not require vitamin K administration, as the bleeding risk remains relatively low at this level 1, 2
• The American Heart Association guidelines specify that for INR 3.0-5.0 without bleeding, the appropriate management is to withhold 1-2 doses and reduce the weekly dose by 10-20% 1
• The risk of bleeding increases exponentially with INR values above 3.0, but becomes clinically significant primarily when INR exceeds 5.0 2

Specific Dosing Algorithm

Current weekly dose calculation:

• Sunday: 3 mg
• Monday-Saturday: 5 mg × 6 days = 30 mg
• Total: 33 mg/week

Recommended adjustment:

• Reduce weekly dose by 10-15% = 29.7-30 mg/week 1
• Practical regimen: 3 mg on Sunday and Thursday, 5 mg on remaining 5 days = 28 mg/week
• Alternative: 3 mg on Sunday, Monday, Thursday; 5 mg on remaining 4 days = 29 mg/week

Monitoring Strategy

• Withhold 1 dose of warfarin immediately 1
• Recheck INR in 3-5 days after implementing the dose reduction 3
• Once INR stabilizes in therapeutic range (2.0-3.0), continue monitoring every 1-2 weeks initially, then extend to every 4 weeks if stable 1
• Do NOT wait 1-2 weeks for the first recheck—this is a common pitfall that can lead to continued supratherapeutic anticoagulation 3

Critical Pitfalls to Avoid

• Do not administer vitamin K for INR 3.2 without bleeding, as this is unnecessary and can cause warfarin resistance 1, 4
• Do not make excessive dose reductions (>20% weekly dose change), as this can lead to subtherapeutic anticoagulation and increased thrombotic risk 3, 4
• Do not ignore a single elevated INR even if minimally above range—a dose adjustment is warranted to prevent further INR elevation 1, 2
• Avoid simply withholding warfarin without dose adjustment, as resuming the same dose will likely result in recurrent supratherapeutic INR 1

When Vitamin K Would Be Indicated

Vitamin K is NOT needed in this scenario, but would be appropriate if: 1, 4

• INR >5.0 without bleeding: oral vitamin K 1-2.5 mg
• INR >9.0 without bleeding: oral vitamin K 2.5-5 mg
• Any INR with active bleeding: IV vitamin K 5-10 mg plus consideration of prothrombin complex concentrate

Factors to Investigate

Before resuming warfarin, identify potential causes of INR elevation: 1

• Recent medication changes (antibiotics, antifungals, NSAIDs are common culprits)
• Dietary changes in vitamin K intake (decreased green leafy vegetables)
• Intercurrent illness (fever, diarrhea, decreased oral intake)
• Alcohol consumption changes
• Medication adherence issues