Clinical and applied thrombosis/hemostasis : official journal of the International Academy of Clinical and Applied Thrombosis/Hemostasis
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Clin. Appl. Thromb. Hemost. · Oct 2004
Anti-Xa and anti-IIa drugs alter international normalized ratio measurements: potential problems in the monitoring of oral anticoagulants.
Several of the newly developed anti-Xa and anti-IIa agents have been shown to influence the International Normalized Ratio (INR) values. During phase I trials with normal healthy volunteers and phase II study patients who were given warfarin and concomitant anti-IIa or anti-Xa agents, it has been reported that INR values were falsely elevated. It is of critical importance to know of the effects of these agents on INR to avoid dosage errors. ⋯ Because of the false elevation of INR values with some of the non-oral anticoagulant drugs, patients who are on concomitant warfarin therapy should be carefully evaluated for their corresponding INR values for proper dosing. To avoid dosing errors it is best not to use the INR values in the therapeutic monitoring of anti-Xa and anti-IIa agents either in the monotherapeutic or polytherapeutic modalities. These data also warrant the development clinically relevant methods for the monitoring of the concomitant use of newly developed anti-Xa and anti-IIa drugs with oral anticoagulants.