Warfarin Toxicity: Causes and Management in Pasang Hospital, Lamphun Province, Thailand

Abstract

This study aims to determine the causes and management of warfarin toxicity in outpatients who visited an anticoagulation clinic at Pasang Hospital, Lamphun, Thailand. This is a retrospective review of all outpatients who visited the anticoagulation clinic at Pasang Hospital between 1 January to 31 December 2018 with an international normalized ratio (INR) >3.0 and 3.5 in patients who have undergone mechanical mitral valve replacement. During the study period, 267 increased INR measurements (138 patients) met the inclusion criteria for warfarin toxicity. The prevalence of warfarin toxicity was 18.6% (267/1,434). The causes of warfarin toxicity were identified and addressed in 96.3% (257/267) of patients. Where the causes were identified, 57.1% (237/415) were due to drug-disease interaction and unstable underlying disease, and 36.6% (152/415) were due to drug-drug interaction. Major bleeding occurred in 3.7% (10/267) of patients. The management of patients who presented with warfarin toxicity depended on the degree of INR elevation and the severity of bleeding. Physicians’ adherence to the recommendations from published literatures was almost 100% (266/267) of patients. The INR value decreased in all patients (100%, 267/267) after the intervention given. In conclusion, warfarin toxicity is quite common and is best managed by a multidisciplinary team in order to prevent warfarin toxicity effectively.