Factors influencing warfarin overdose in warfarin clinic of Satuek Hospital, Buriram Province

Abstract

This paper is aimed to study the factors that affect Warfarin overdose and its consequences. Samples were patients registered in the Warfarin clinic, Satuek Hospital who had INR more than 3.0 if they did not have Valve Replacement Surgery and INR more than 3.5 if they had Valve Replacement Surgery. There were 134 patients having abnormal INR in 2013. Questionnaire was used and descriptive statistics were expressed as frequency, percentage, mean, median and standard deviation. X²-test, Student T Test and Multiple Linear Regression were used to find the independent variables enhancing INR. Among them, 42.4 % were females. Majority of INR falling in the range from 3.0 to 4.0 was found in 63.7 %. The average Warfarin dosage was 23.1+4.1 mg/week. The most common indication was Atrial fibrillation found in 95.8 %. Around 35 % of patients took medicine improperly and the common unwanted symptoms such as bruises were found in 18.8 %. The low BMI (BMI < 20 kg/m²) and the Warfarin dosage of >20 mg/week were the two common causes of the INR ranging between 3.0-4.0 but no statistical significance (P=0.92 and 0.46, respectively) whereas the age over 60 years was the most common cause of INR ranging between >4.0-5.0 but no statistical significance (P=0.66). Focus on diseases relating to increased INR, heart failure had higher risk of INR > 3 with statistical significance (odd ratio =1.108, P <0.001). Moreover, it was found that the more chronic diseases, the stronger relation with increased INR (r =0.351, P= 0.002). In conclusion, the risk factors contributing Warfarin overdose are age > 60 years, BMI < 20 kg/m², hypertension, heart failure, GFR below 60 ml/min, Warfarin > 20 mg/week and patients with many chronic diseases so they should be treated carefully in order to prevent Warfarin overdose.