Therapeutic drug monitoring of direct oral anticoagulants (DOAC)/UHPLC method for simultaneous determination of direct oral anticoagulants in human plasma

The development of three new oral anticoagulants: Apixaban, Dabigatran and Rivaroxaban promised to be a big step forward in pharmacotherapy. Fixed dosage and a no longer need for tight monitoring of the INR value because of superior pharmacokinetics seem to offer quite an advantage compared to their older counterparts Phenprocoumon and Warfarin. But is there really no need for monitoring? Or is the producers marketing and the lack of a reliable method the real reason for this apparent advantage. Dabigatran has a low bioavailability and needs to be bio activated. Rivaroxaban and Apixaban are both substrates of CYP3A4. This seems especially critical in psychiatry where polymedication with CYP450-inhibiton is quite common. We used protein precipitation with acetonitrile (1:2) for sample preparation. The method was developed using a RP-C18 column. Eluent (A) was acetonitrile and eluent (B) was water. A gradient run was performed at 30°C starting with 98% (B) and gradually changing to (B) 0% over 5,0 min. Detection was achieved via UV-Vis with absorption maxima at 249 nm, 280 nm and 307 nm. We developed a rapid UHPLC method for simultaneous quantification of all three drugs in human plasma, in presence with common psychiatric drugs, within a 6 minute run. Future plans are the measurement of patient samples to determine a correlation between plasma levels and risk of bleeding as well as the effect of enzyme inhibition on the plasma concentration of the new anticoagulants.