Oral anticoagulant therapy: practical aspects of management

Careful attention to the practical aspects of oral anticoagulant therapy can improve patient compliance and lessen the risk of bleeding complications. A variety of risk factors for bleeding associated with oral anticoagulant therapy have been defined and should be assessed before initiating therapy. Recent investigations have provided a means for estimating what constitutes a significant change in an individual patient's serial International Normalized Ratio (INR) by allowing for combined analytic and biologic variation in prothrombin time determinations. Dosing adjustments with warfarin sodium (Coumadin, Panwarfin, Sofarin) should be appropriate to the level of the INR and spread over the total weekly dosage for optimum stable control. Elderly patients are more sensitive to any given dose of warfarin and need a significantly lower total weekly dose. Attention must be paid to the vitamin K content of the diet and a variety of additional factors, including other drug therapy, alcohol consumption, and metabolic status. Hematuria or gastrointestinal bleeding should always be assessed, because the chance of finding a clinically significant lesion is good, especially when the INR has been in the therapeutic range. Although a minor prolongation of the INR without bleeding may be treated by watchful waiting, vitamin K administration and other therapeutic measures may be necessary for active bleeding. Comprehensive patient education is paramount and may be facilitated by a checklist approach. A well-informed patient provides one of the best defenses against bleeding complications.