Providing confidence when measuring blood levels of the new direct oral anticoagulants

Direct oral anticoagulants (DOAC) are set to replace the complicated dosing regimens of warfarin for preventing and treating stroke, atrial fibrillation and venous thromboembolism. The four DOACs currently available are rivaroxaban, apixaban, edoxaban and dabigatran. These drugs are seen as effective and safe as a vitamin K antagonist (VKA) such as warfarin,^1–3 without the considerable intra-individual variation in dose requirement.

Their highly predictable pharmacokinetic profile means that they can be prescribed at a fixed dose, once or twice daily, without the need for routine monitoring. This offers the patient greater convenience, with the condition easier to manage both for healthcare providers and the patients themselves. A short half-life and rapid onset, so avoiding bridging strategies, are other clear benefits.

The effectiveness of DOACs is not impaired by diet, and fewer drugs appear to interact with them, albeit with some concerns over the actual effect of P-glycoprotein inhibitors.⁴ In addition, there is still some debate over therapeutic ranges. The first reversal agent, idarucizumab (specific to dabigatran), has recently been licensed in the UK, but direct anti-Xa reversal agents are still in trial.