Managing Oral Anticoagulant Therapy

Abstract

S everal important developments in the last 2 decades have improved clinical outcomes with oral anticoagulation therapy and have led to an appropriate increase in the use of this therapy by improving its safety. These developments include defining the appropriate indications for oral anticoagulation through the results of large randomized trials, 1,2 identifying the optimal therapeutic range and reporting format (ie, international normalized ratio [INR]) to maximize safety and effectiveness, 3‐16 and managing the dose of therapy to achieve the maximal time in therapeutic range (TTR). 17‐19 The intensity of therapy and the TTR are two of the most important determinants of therapeutic effectiveness and of reducing hemorrhagic risk. Ideally, the INR should be kept in the therapeutic range most of the time, but many factors influence the attainment of this goal. These include physiologic and pharmacologic factors, such as interacting drugs or illnesses that affect the pharmacokinetics or pharmacodynamics of warfarin, dietary or GI factors that affect the availability of vitamin K1, or physiologic factors that affect the synthetic or metabolic fate of the vitamin K-dependent coagulation factors. Patient-specific factors such as adherence to a therapeutic plan are also important. Last, the physician’s ability to make appropriate dosing and follow-up decisions will have a profound impact, if such decisions are incorrect. The comprehensive management of these variables requires a knowledgeable provider, an organized system of follow-up, reliable prothrombin time (PT) monitoring, and good patient communication and education. This article focuses on dosing management and models of care, and it reviews the evidence that indicates that an organized approach to anticoagulant management leads to better outcomes.