Associated Factors and Safety of the Rapidly Achieving First Therapeutic Target of Warfarin in hospitalized Patients: A Retrospective Cohort Study

Background: Warfarin is a commonly used anticoagulant drug in clinical practice. Rapidly achieving the first therapeutic international normalized ratio (INR) of warfarin may reduce the hospital length of stay. However, little research has been carried out to evaluate the influencing factors and the safety of rapidly achieving the first therapeutic INR target of warfarin. Aim To investigate the associated factors and the safety of rapidly achieving the first therapeutic INR target of warfarin. Method A retrospective cohort study was conducted in inpatients who took warfarin from November 2018 to October 2019. Patients’ information was retrieved from medical records. Results 487 patients were included. The mean achieving first therapeutic target time was 6.0 ± 3.2 days (median, 5.0 days). Age > 65 years, body mass index < 24 kg/m 2 , and initial warfarin dose ≥ 3 mg/d were independent factors associated with the rapidly achieving first INR target of warfarin therapy. The incidence of INR ≥ 4 was higher in patients achieving the first INR target rapidly than those achieving the first INR target slowly, while there were no significant differences in bleeding events between the two groups. Conclusion Hospitalized patients aged > 65 years, with a body mass index < 24 kg/m 2 , or receiving an initial warfarin dose ≥ 3mg/d were more likely to achieve the first INR target of warfarin rapidly. Closer INR monitoring and appropriate warfarin dose adjustment are recommended to improve the safety for patients achieving the first INR ≥ 1.8 within 6 days after beginning oral warfarin.