연령별 적정 와파린 용량 설정에 관한 연구 = Evaluation of Warfarin Initial Dosing in Korean Patients

다국어 초록 (Multilingual Abstract)

American College of Chest Physicians has recommended reasonable initial dose of warfarin therapy in outpatients, which is at least 5 mg/day for adults and less than 5 mg/day for the elderly. Meanwhile Anti-coagulation Service (ACS) of Samsung Medical Center (SMC) has set up its own guideline in warfarin therapy: warfarin 2 mg/day for over 70-year-old patients, 2.5 mg/day for under 70-year-old patients, followed by checking INR within one week. This was obtained clinically, and its property has not been evaluated. In this context, the purpose of this study is to analyze age-related maintenance dosing pattern and multiple factors of warfarin effect and provide useful information for a standard dose guideline to ACS of SMC. Study I was processed as follows. First, targeted patients were the department of neurology and internal circulatory patients enrolled at ACS. And then, divided into two groups by their specific INR; INR of group I is 1.7 to 2.5 and that of group Ⅱ is 2.0 to 3.0. In study II, patients who had received warfarin therapy in ACS of our out-patient medical center and had indication of atrial fibrillation, at the same time, showing INR 2.0~3.0 were investigated. This study was performed under SAS 3.0 version. For this study, 288 (group Ⅰ) and 220 (group Ⅱ) patients' records were analysed. From the view of age factor, the elderly in both groups needed significantly lower warfarin dose (Ⅰ,Ⅱ: p ＜0.0001) and the maintenance warfarin dose for male was significantly greater than that of female in group Ⅰ(p＜0.05). On the contrary, male did not differ from female in their warfarin requirements in group Ⅱ. In weight respect, there was positive relationship between the body weight and required dose (Ⅰ,Ⅱ: p＜0.05), however it did not relate to BMI. In study Ⅱ, under 70-year-old patients needed 33.4 days and over 70-year-old patients needed 28.7 days in order that their INR reaches the target range. In this study, we confirmed that the age of the patient is the most important determinant of warfarin requirement in Korean. We also found required warfarin dose decreased averagely 0.35 mg/week for each additional aged patient and Korean warfarin patients required lower warfarin dose such as 2.2~7 mg/week compared to Caucasian. It means there are ethnic difference. All things considered, this study allowed new guideline for initiating warfarin dose, especially for atrial fibrillation patients whose target INR is 2.0~3.0 and resulted in the age-related maintenance dose like followings; under 50 years old: 3.5 mg/day, 50~59 years old: 3 mg/day, 60~69 years old: 2.5 mg, over 70 years old: 2 mg. Further investigation needs to be conducted to confirm how much the required period to reach INR is shortened when the newly recommended doses are applied.