What dose of warfarin (Coumadin) should be given today to a patient with atrial fibrillation and an International Normalized Ratio (INR) of 2.7, who has been withheld from Coumadin, to maintain a therapeutic INR range of 2 to 3?

Warfarin Dosing Today for INR 2.7 After Withholding

Resume warfarin at your patient's usual maintenance dose today—no dose adjustment is needed for an INR of 2.7, which sits comfortably within the therapeutic range of 2.0-3.0 for atrial fibrillation. 1, 2

Rationale for Full Maintenance Dose

• Your patient's INR of 2.7 is therapeutic and optimal. The American College of Chest Physicians recommends targeting an INR of 2.5 (range 2.0-3.0) for atrial fibrillation, and your patient is already at this ideal target 1, 2

• Brief warfarin interruption does not require loading doses when restarting. Guidelines explicitly recommend resuming at the known maintenance dose after temporary interruption 3, 4

• The INR will naturally decline over the next 2-3 days if warfarin remains withheld. Given the half-life of warfarin and vitamin K-dependent clotting factors, delaying restart or using reduced doses risks subtherapeutic anticoagulation 4

Key Management Points

Monitoring schedule:

• Recheck INR in 3-5 days after resuming warfarin to ensure the patient remains in therapeutic range 5, 4
• If the INR was therapeutic before interruption and the patient resumes the same maintenance dose, expect return to steady-state within approximately one week 6

Common pitfall to avoid:

• Do not reduce the dose simply because the current INR is "high-normal" at 2.7. This INR represents optimal anticoagulation for stroke prevention in atrial fibrillation, and reducing the dose would likely result in subtherapeutic anticoagulation (INR <2.0), which significantly increases thromboembolism risk 1, 5

When to consider dose adjustment:

• Only adjust the maintenance dose if the patient's INR consistently runs above 3.0 or below 2.0 on their current regimen 5, 4
• A single INR value of 2.7 after brief interruption does not indicate the need for any dose modification 5, 4

Special consideration for elderly patients:

• If your patient is over 75 years old, they may be more sensitive to warfarin and could require slightly lower maintenance doses (approximately 1 mg/day less than younger patients) 7
• However, this sensitivity should already be reflected in their established maintenance dose, so no additional adjustment is needed today 7