Warfarin Dosing and Time Required to Reach Therapeutic International Normalized Ratio in Patients with Hypercoagulable Conditions

Abstract

Objective: The purpose of this study was to analyze the difference in duration of anticoagulation and dose of warfarin required to reach a therapeutic international normalized ratio [(INR) of 2 to 3] in patients with hypercoagulable conditions as compared to controls. To our knowledge, this study is the first in the literature to delineate such a difference. Materials and Methods: A retrospective chart review was performed in a tertiary care hospital. The total study population was 622. Cases (n=125) were patients with a diagnosis of a hypercoagulable syndrome who developed venous thromboembolism. Controls (n=497) were patients with a diagnosis of venous thromboembolism in the absence of a hypercoagulable syndrome and were matched for age, sex, and race. Results: The total dose of warfarin required to reach therapeutic INR in cases was higher (50.7+-17.6 mg) as compared to controls (41.2+-17.7 mg). The total number of days required to reach therapeutic INR in cases was 8.9+-3.5 days as compared to controls (6.8+-2.9 days). Both of these differences were statistically significant (p<0.001). Conclusion: Patients with hypercoagulable conditions require approximately 10 mg of additional total warfarin dose and also require, on average, 2 extra days to reach therapeutic INR as compared to controls.

Keywords

• international normalized ratio
• warfarin
• hypercoagulable conditions
• venous thromboembolism