Warfarin therapeutic monitoring: is 70% time in the therapeutic range the best we can do?

Summary Heavier than air flying machines are impossible. Lord Kelvin, President, Royal Society of England, 1895 What is known and Objective: Warfarin, an oral anticoagulant, which has been in clinical use for over sixty years, remains a challenge for clinicians to utilize, given the multiplicity of items which can limit its efficacy. Our objective is to review the evidence and comment on whether INR control can be better than has been currently reported in various studies. Comment: The duration of time a patient’s international normalized ratio (INR) is maintained within the therapeutic range (time in the therapeutic range, TTR) for his or her particular indication for the drug impacts the effectiveness and safety of warfarin therapy. Maintaining a therapeutic INR while on warfarin is difficult, and numerous studies employing various strategies confirm the challenge, but not the impossibility of achieving a TTR above 70%. What is new and Conclusion: Maintaining a therapeutic INR requires a dedicated multi‐faceted approach. With diligence, skill and various therapeutic strategies, a TTR >70% can be achieved.