Oral Anticoagulant Initiation: Rationale for the Use of Warfarin Dosing Nomograms

Oral anticoagulants prevent thrombosis however they are associated with bleeding. The risk of both bleeding and thrombosis is increased when the International Normalized Ratio (INR) is outside the desired therapeutic range. Hence, oral anticoagulants should be administered with the intention of maximizing the "time within the therapeutic range." The frequency of INR values outside this range can be decreased by (1) warfarin initiation algorithms that guide initial therapy and (2) use of computerized systems to guide chronic warfarin therapy. This article reviews these techniques.