Factors Influencing International Normalized Ratio in Patients Anticoagulated With Warfarin(Special Issue in Hornor of the Retirement of Professor Makoto Iwata at the Department of Neurology, Tokyo Women's Medical University)

Preventive effect of warfarin for the development of cardiogenic embolism is well established. However, variability in the required dose for each individual makes it difficult to prescribe adequate dose of warfarin because of the potential risk of hemorrhage. In the present study, we retrospectively evaluated relationship between the international normalized ratio (INR) and several patient-specific clinical factors such as gender, age, body weight, patient's medical status, risk factors for stroke, renal/liver function, and hemostatic markers. Eighty-six patients (55: men, 31: women, mean age of 68 years) anticoagulated with oral warfarin between April 2004 and March 2006 were entered in the study. Among patient-specific factors, we analysed factors influencing INR during warfarin therapy. Under warfarin treatment, three factors were associated with increased INR/mg ratio; body weight<40 kg, coagulopathy, and renal failure. In contrast, following factors decreased INR/mg ratio; age < 50 years, body weight &ge;80 kg, and increased levels of platelet activation markers