Target INR for DVT on Warfarin Therapy

Therapeutic Range and Target

• The American College of Chest Physicians recommends a therapeutic INR range of 2.0 to 3.0, with a target of 2.5, for patients with deep vein thrombosis (DVT) treated with warfarin, based on moderate-certainty evidence 1
• The American Society of Hematology provides a strong recommendation for this INR range over lower ranges, such as 1.5 to 1.9, for DVT patients 2, 3

Evidence Supporting This Range

• Using an INR range lower than 2.0 to 3.0 significantly increases the risk of recurrent DVT, with a relative risk of 3.25, and 24 more DVT events per 1000 patients 2
• Lower INR ranges may increase the risk of pulmonary embolism, with a relative risk of 5.0, and mortality, with a relative risk of 2.0, though these did not reach statistical significance 2

Initiation and Bridging Requirements

• The American College of Chest Physicians recommends starting warfarin early, on the same day as parenteral anticoagulation, and overlapping with parenteral therapy for a minimum of 5 days, and until INR is ≥2.0 for at least 24 hours 1
• The bridging period is critical because warfarin initially creates a prothrombotic state before achieving therapeutic anticoagulation 5

Common Pitfalls to Avoid

• Historical INR targets below 2.0, such as 1.7 or 1.8, are not validated for safety or efficacy and should be avoided, according to the Journal of Thrombosis and Haemostasis 6, 7
• Failing to bridge with LMWH when INR is subtherapeutic increases recurrent thrombosis risk 4

Special Considerations

• For cancer-associated DVT, LMWH monotherapy is preferred over warfarin when possible, but if warfarin is used, the same INR target of 2.0-3.0 applies 5
• Higher INR ranges, such as 3.0-4.5, are not recommended for DVT and increase bleeding risk without additional benefit, according to the American College of Chest Physicians 1