Initiating warfarin therapy

Initiating warfarin in warfarin-naïve patients continues to be a clinical challenge. Present approaches require some degree of data extrapolation or assumptions to justify benefits. Use of LMWHs or indirect Xa inhibitors can ease the process for many patients, resulting in a smoother transition to warfarin or its avoidance altogether. Additional agents on the horizon, such as the oral direct thrombin inhibitor xi-melagatran, may provide even easier initiation of long-term anticoagulation therapy. Despite this, there will still be individuals requiring warfarin. Nomograms and computer-assisted programs can be useful aids, but by their limiting design, are situation specific. Thus, there is a need for validation in larger samples with control comparisons, clearly identifying any limitations. Their use should not completely replace a careful assessment of each patient's clinical presentation or anticoagulation needs, especially when these include physiologic factors, concurrent drug interactions, or other sensitivity factors that may not have been taken into consideration. Each patient should therefore be individually and carefully assessed for risks of bleeding or thrombosis and benefits of anticoagulation therapy. The true degree of anticoagulation represented by an INR value must also be considered. Initial dosing plans should include these considerations and be adjusted with the tools and resources available to optimize therapy. No complete foolproof method that works for almost every patient is currently (and most likely not in the near future) available. When using adjunct nomograms, computer programs, or other tools to derive a warfarin dose prior to reaching steady-state, knowledge of their benefits and limitations should be incorporated into the final dose determination.