Laboratory tests during direct oral anticoagulant treatment? No

The vexed question of whether or not to measure levels of direct oral anticoagulants before surgery or invasive procedures

Direct oral anticoagulants (DOAC) possess high bioavailability, and their anticoagulant effect is more predictable than that of vitamin K antagonists, hence they do not require routine dose adjustment based on laboratory testing. However, there are circumstances when laboratory testing may be useful, including patients who need to undergo surgery or invasive procedures. Most guidelines state that patients on DOAC may safely undergo surgery/invasive procedures by stopping anticoagulation for a few days before intervention without testing if renal function is within normal limits. This review article discusses the pros and cons of measuring (or not measuring) DOAC levels before surgery/invasive procedures by a multidisciplinary team of experts with different background, including the thrombosis laboratory, clinical thrombosis, internal medicine, cardiology and nephrology. The conclusion is that measuring DOAC with dedicated tests before surgical or invasive procedures is important for patient safety. It provides the best and most direct evidence to rule in (or to rule out) clinically relevant concentrations of residual drugs. Regulatory agencies should urgently approve their use in clinical practice. Hospital administrators should make them available, and clinical laboratories should set up the relative methods and make them available to clinicians.

Old and new oral anticoagulants: Food, herbal medicines and drug interactions

The most commonly prescribed oral anticoagulants worldwide are the vitamin K antagonists (VKAs) such as warfarin. Factors affecting the pharmacokinetics of VKAs are important because deviations from their narrow therapeutic window can result in bleedings due to over-anticoagulation or thrombosis because of under-anticoagulation. In addition to pharmacodynamic interactions (e.g., augmented bleeding risk for concomitant use of NSAIDs), interactions with drugs, foods, herbs, and over-the-counter medications may affect the risk/benefit ratio of VKAs. Direct oral anticoagulants (DOACs) including Factor Xa inhibitors (rivaroxaban, apixaban and edoxaban) and thrombin inhibitor (dabigatran) are poised to replace warfarin. Phase-3 studies and real-world evaluations have established that the safety profile of DOACs is superior to those of VKAs. However, some pharmacokinetic and pharmacodynamic interactions are expected. Herein we present a critical review of VKAs and DOACs with focus on their potential for interactions with drugs, foods, herbs and over-the-counter medications.

Gastrointestinal bleeding in patients receiving oral anticoagulation: Current treatment and pharmacological perspectives

Gastrointestinal bleeding (GIB) is a potentially fatal and avoidable medical condition that poses a burden on global health care costs. The rate of major GIB related to the use of some direct acting oral anticoagulant drugs (DOACs), is higher than that detected in warfarin users. Current strategies in the treatment of GIBs in patients receiving warfarin or DOACs (vitamin K, activated charcoal; hemodialysis; recombinant factor VIIa; [activated] prothrombin complex concentrates) including indications for the treatment of bleeding based on different degrees of severity of the episodes, is reported in this article. Potential preventive strategies to mitigate the risk of GIBs (e.g. upper endoscopy/biopsy, colon cancer screening; eradication of Helicobacter pylori prior to starting anticoagulation; use of proton-pump inhibitors, identification of risk factors for bleeding) are also reported as well as the fact that some of them have not been tested so far in patients receiving DOACs. Antidotes that experimentally reverse the anti-coagulant effect of dabigatran (Idarucizumab; BI 655075; Boehringer Ingelheim); of rivaroxaban, apixaban, or edoxaban (Andexanet alfa, r-Antidote, PRT064445; Portola Pharmaceuticals) or of all DOACs (Aripazine, PER-977, ciraparantag; Perosphere Inc.) are discussed. Likewise, population pharmacokinetics modeling related to the rate of major DOACs-related GIBs is presented. It is also emphasized that the occurrence of GIB reflects the presence of patients at the highest risk for adverse outcomes. Finally, the implications of the concept that patient characteristics and the severity of illness (i.e. comorbidities) exert a greater impact on the risk of GIB than the type of antithrombotic agent employed, are analyzed.

Antithrombotic drugs, patient characteristics, and gastrointestinal bleeding: Clinical translation and areas of research

Gastrointestinal bleeding (GIB) is a potentially fatal and avoidable medical condition that poses a burden on global health care costs. Current understanding of the roles of platelet activation and thrombin generation/activity in vascular medicine has led to the development of effective antithrombotic treatments. However, in parallel with a sustained coronary and cerebral flow patency, the increasingly intensive treatment with warfarin; direct oral anticoagulant drugs [DOACs], and/or with aspirin ± clopidogrel (or ± prasugrel or ± ticagrelor), has increased the burden of GIBs related to the use of antithrombotic agents. Compelling evidence concerning this issue is accumulating to indicate that: 1) the risk of GIB related to the use of antithrombotic drugs dramatically differs in different clinical settings; and 2) the characteristics of patients (e.g., severity of illness, comorbidities) in whom it is used exert a greater impact on the risk of GIB than the type of antithrombotic agent employed. The latter concept argues for the occurrence of GIB as reflecting the presence of patients at the highest risk for adverse outcomes. The HAS-BLED score identifies subjects at risk of bleeding among those untreated and those treated with warfarin, DOACs and/or low-dose aspirin. Its use within the frame of a severity score (e.g., the CHA2DS2-VASc score in patients with atrial fibrillation) helps balance the benefits and the risks of an antithrombotic treatment and identify those patients in whom the absolute gain (vascular events prevented) outweighs the risk of GIB. Potential implications of the latter information in settings other than atrial fibrillation is thoroughly discussed.

The value of inhibitors of factor Xa for the treatment of pulmonary embolism

The introduction of factor Xa inhibitors advocated the initiation of clinical trials that addressed the value of anticoagulation in patients with hemodynamically stable primary pulmonary embolism (PE). In the Matisse trial in patients with PE, fondaparinux administered at therapeutic doses followed by vitamin K antagonists (VKA) has shown a comparable efficacy and safety profile to that seen with intravenous adjusted-dose unfractionated heparin/VKA. A long-acting derivative of fondaparinux, idraparinux, failed to achieve similar results. On the other hand, the Cassiopea study revealed that once weekly injections of idrabiotaparinux, a slightly modified form of idraparinux, have similar efficacy and better safety profile compared to VKAs in the long-term treatment of patients with PE. However, the inconvenient parenteral administration of both fondaparinux and idrabiotaparinux limits their routine clinical use. The availability of antithrombotic compounds that can be administered orally in fixed dose, owing to their predictable pharmacokinetics and pharmacodynamics, and have a lower potential for drug and food interactions has opened new horizons for the treatment of patients with PE. The Einstein PE, Amplify and Hokusai studies, conducted with rivaroxaban, apixaban and edoxaban, respectively, showed that for the treatment of PE they possess a more favorable benefit-to-risk profile than the conventional antithrombotic drugs. In addition, rivaroxaban and apixaban make it possible to treat uncomplicated PE patients from the beginning, without the need for the parenteral administration of heparins or fondaparinux, and edoxaban allows the treatment of fragile patients with lower doses. All of them cover a wide spectrum of clinical presentations, including PE patients at intermediate risk.