Effectiveness and safety of a 10mg warfarin initiation nomogram in Asian population

Anticoagulant responses to warfarin vary among patients, based on genetic factors, diet, concomitant medications, and disease state. We evaluated the effectiveness and safety of a 10mg warfarin initiation nomogram in an Asian population. Retrospective cross-sectional audit studies were conducted from March 2009 to March 2010. The use of a 10mg-loading dose to initiate warfarin treatment resulted in 33(84.6%) patients attaining a therapeutic INR within four days (mean time, 2.6 days). There was no significant correlation between age, gender, race, and serum albumin for the time to reach a therapeutic INR. A significant correlation was noted for patient's baseline INR and time to reach a therapeutic INR (P<0.05). No significant differences were observed in time to reach a therapeutic INR in patients treated with specific class of concomitant drugs or patients with specific disease states. The overall incidence of over-anticoagulation was 35.9%; however, no bleeding episodes were encountered. In conclusion, the use of a 10mg warfarin nomogram was effective in rapidly achieving a therapeutic INR. However, the nomogram's safety is debatable owing to the high over-anticoagulation rate warfarin-administered patients. Caution is recommended in the initiation of warfarin treatment using the 10mg nomogram.