28 Dec 2021
byDr. Lim Lay Cheng
Venous thromboembolism (VTE) is a serious medical condition. It comprises deep vein thrombosis and pulmonary embolism. Left untreated, it could result in significant morbidity and mortality. Most patients with VTE receive anticoagulation therapy for 3 months or longer. For more than 50 years since the 1940s, vitamin K antagonists (VKAs) such as warfarin were the mainstay of oral anticoagulation therapy for VTE. As it has a narrow therapeutic index, VKAs require frequent coagulation monitoring with International Normalised Ratio (INR) to adjust and optimize the dose for each individual. As the peak effect for warfarin takes at least 4-5 days, in the initial stage of VTE, concurrent administration of daily subcutaneous injections of low molecular weight heparin (LMWH) is needed until INR reaches therapeutic levels. Due to numerous drug and dietary interactions with warfarin, regular INR monitoring is required to ensure therapeutic levels are maintained and to avoid under or overdosing.