Abstract 16499: Initial Prothrombin Time Response After Warfarin Loading as a Major Determinant Influencing Maintenance Dose
Introduction: Warfarin is still the most commonly used oral anticoagulant, but the standardization of its dosing is difficult due to wide variability in dose-response relation among the patients.
Hypothesis: Initial prothrombin time response to warfarin loading has the potential to predict the maintenance dose because it incorporate both genetic trait and acquired factors related to dose requirement.
Methods: In retrospective cohort design, 65 patients were studied in whom anticoagulation was started with 3 day loading of warfarin 5 mg/day and stable maintenance dose was achieved during follow-up. International normalization ratio (INR) was measured, and demographic and clinical parameters were collected for the analysis.
Results: In study subjects, the INR values after loading and at maintenance were1.65+/-0.29, 2.42+/-0.54, respectively. Warfarin maintenance dose was 2.69+/-1.10 mg/d. There was significant negative relation between the initial INR after loading and maintenance dose of wafarin (Figure, r=0.523, P<0.001). In the multiple regression, the INR value after loading(P<0.001), patient gender(P=0.009), body weight (P=0.041) were significantly correlated with maintenance dose of warfarin. Therefore, an equation was formulated from the regression: Maintenance warfarin dose (mg) = 4.240 - 1.895 x INR after loading + 0.650 x male(1) + 0.023 x weight(kg) - 0.012 x age(year).
Conclusions: Among the factors influencing warfarin dose requirement, INR value after loading exhibited strong negative correlation with maintenace dose during follow-up. Accordingly, an equation for predicting maintenance dose could be formulated. Further study enrolling large population is needed to validate this correlation.
Author Disclosures: Y. Kim: None. Y. Cho: None. K. Park: None. J. Park: None. T. Park: None. J. Ahn: None. E. Jeong: None.
- © 2014 by American Heart Association, Inc.