New oral anticoagulants for the treatment of venous thromboembolism: understanding differences and similarities.

Venous thromboembolism (VTE) is a major cause of morbidity, mortality, and healthcare expenditure. In the United States, approximately 0.1 % of the population experiences an initial VTE event each year. Anticoagulation therapy is the cornerstone of acute VTE treatment and for prevention of recurrent VTE events. Conventional anticoagulants, including heparin, low-molecular-weight heparins, fondaparinux, and vitamin K antagonists are widely used but have limitations. Newer oral anticoagulant agents, including direct thrombin inhibitors (e.g., dabigatran etexilate) and direct factor Xa inhibitors (e.g., rivaroxaban, apixaban, and edoxaban) have been developed to attempt to overcome some of the limitations of conventional anticoagulant therapy. These new oral agents have been evaluated for safety and efficacy in large, randomized clinical trials in the treatment and secondary prevention of VTE with results that are comparable to conventional therapy. Dabigatran, rivaroxaban, apixaban, and edoxaban are important new treatment options for patients with VTE. In this review, we compare these new agents and their associated clinical trials in VTE treatment

Clinical use of rivaroxaban: pharmacokinetic and pharmacodynamic rationale for dosing regimens in different indications.

Target-specific oral anticoagulants have become increasingly available as alternatives to traditional agents for the management of a number of thromboembolic disorders. To date, the direct Factor Xa inhibitor rivaroxaban is the most widely approved of the new agents. The dosing of rivaroxaban varies and adheres to specific schedules in each of the clinical settings in which it has been investigated. These regimens were devised based on the results of phase II dose-finding studies and/or pharmacokinetic modeling, and were demonstrated to be successful in randomized, phase III studies. In most cases, the pharmacodynamic profile of rivaroxaban permits once-daily dosing. A once-daily dose is indicated for the prevention of venous thromboembolism (VTE) in patients undergoing hip or knee replacement surgery, the long-term prevention of stroke in patients with non-valvular atrial fibrillation, and the long-term secondary prevention of recurrent VTE. Twice-daily dosing is required in the acute phase of treatment in patients with VTE and in the combination of rivaroxaban with standard single or dual antiplatelet therapy for secondary prevention after acute coronary syndrome events. This article reviews the empirical and clinical rationale supporting the dose regimens of rivaroxaban in each clinical setting

Direct Oral Anticoagulants for the Prevention of Stroke in Patients with Nonvalvular Atrial Fibrillation: Understanding Differences and Similarities.

The presence of atrial fibrillation (AF), the most common sustained cardiac arrhythmia, significantly increases the risk for stroke. Current guidelines recommend that the vitamin K antagonist warfarin or direct oral anticoagulants (DOACs), such as the approved direct thrombin inhibitor dabigatran and the approved direct factor Xa inhibitors apixaban, rivaroxaban, and edoxaban, should be used for thromboprophylaxis in patients with nonvalvular AF at risk for stroke or systemic embolic events (SEE). Warfarin, the mainstay of stroke prevention in AF, increases the risk of major bleeding. Furthermore, warfarin therapy comes with several limitations including frequent monitoring and the need for dose adjustments, unpredictable pharmacokinetics and pharmacodynamics, and the potential for significant drug-drug and food-drug interactions. The DOACs were developed to overcome these limitations while maintaining or surpassing warfarin\u27s efficacy and safety profiles. All four DOACs have similar or better efficacy and safety compared with warfarin and are therefore valuable alternatives for the prevention of stroke and SEE in patients with nonvalvular AF. Understanding the subtle differences in the DOACs\u27 pharmacology, phase 3 study designs, and trial outcomes will allow for a more tailored approach in selecting the right oral anticoagulant for each patient

Ticagrelor: pharmacokinetics, pharmacodynamics, clinical efficacy, and safety.

Dual antiplatelet therapy, composed of aspirin plus a P2Y12 -receptor antagonist, is the cornerstone of treatment for patients with acute coronary syndrome (ACS). A number of U.S. Food and Drug Administration-approved P2Y12 -receptor antagonists are available for treating patients with ACS, including the thienopyridine compounds clopidogrel and prasugrel. Ticagrelor, the first of a new class of antiplatelet agents, is a noncompetitive, direct-acting P2Y12 -receptor antagonist. Unlike the thienopyridine compounds, ticagrelor does not require metabolism for activity. Also, whereas clopidogrel and prasugrel are irreversible inhibitors of the P2Y12 receptor, ticagrelor binds reversibly to inhibit receptor signaling and subsequent platelet activation. In pharmacodynamic studies, ticagrelor demonstrated faster onset and more potent inhibition of platelet aggregation than clopidogrel. These properties of ticagrelor may contribute to reduced rates of thrombotic outcomes compared with clopidogrel, as demonstrated in a phase III clinical trial. However, in addition to bleeding, distinctive adverse effects of this new chemical entity have not been reported with the thienopyridine P2Y12 -receptor inhibitors. Although ticagrelor represents an advancement in P2Y12 -receptor inhibition therapy, a thorough understanding of this compound as an antiplatelet therapy remains to be elucidated

Impact of a high-fat meal on assessment of clopidogrel-induced platelet inhibition in healthy subjects.

BACKGROUND: Ideal conditions for platelet reactivity testing are critical for optimal selection of a P2Y12 inhibitor. Data are inconsistent regarding the impact of high-fat meals on test assessment. METHODS: Participants included 12 healthy subjects not taking antiplatelet drugs after a 12-hour fast. After baseline assessment, subjects were given a 600 mg dose of clopidogrel. Four hours later, maximum platelet inhibition was tested in the fasting state by light transmission aggregometry (LTA), VerifyNow P2Y12, vasodilator-stimulated phosphoprotein (VASP), and whole blood aggregometry (WBA). Subjects were then provided a high-fat meal, and platelet function was evaluated two hours later. Change in measured platelet aggregation by LTA was the primary endpoint of the study. The Wilcoxon Rank Sum test was used to compare the change in platelet reactivity between fasting and non-fasting conditions. The Spearman rho (ρ) correlation coefficient was used to evaluate the association between fasting platelet reactivity and the change following a high-fat meal. RESULTS: No significant change occurred in maximal light transmission, as assessed by LTA with 5 μM ADP (p = 0.15) and with 20 μM ADP (p = 0.07). There was a significant change in the area under the curve with 5 μM ADP (p = 0.03) but not with 20 μM ADP (p = 0.18). Although there was no significant change with the VerifyNow P2Y12 assay (p = 0.16), the change was correlated with the initial fasting value (Spearman\u27s rho p = 0.008). The VASP assay and WBA varied minimally. CONCLUSION: The high-fat meal did not significantly alter platelet function assessment of commonly used platelet function tests. Greater intra-subject variability existed for the optically-dependent compared with non-optically dependent tests. TRIAL REGISTRATION: NCT01307657

Guidance for the practical management of the heparin anticoagulants in the treatment of venous thromboembolism.

Venous thromboembolism (VTE) is a serious and often fatal medical condition with an increasing incidence. Despite the changing landscape of VTE treatment with the introduction of the new direct oral anticoagulants many uncertainties remain regarding the optimal use of traditional parenteral agents. This manuscript, initiated by the Anticoagulation Forum, provides clinical guidance based on existing guidelines and consensus expert opinion where guidelines are lacking. This specific chapter addresses the practical management of heparins including low molecular weight heparins and fondaparinux. For each anticoagulant a list of the most common practice related questions were created. Each question was addressed using a brief focused literature review followed by a multidisciplinary consensus guidance recommendation. Issues addressed included initial anticoagulant dosing recommendations, recommended baseline laboratory monitoring, managing dose adjustments, evidence to support a relationship between laboratory tests and meaningful clinical outcomes, special patient populations including extremes of weight and renal impairment, duration of necessary parenteral therapy during the transition to oral therapy, candidates for outpatient treatment where appropriate and management of over-anticoagulation and adverse effects including bleeding and heparin induced thrombocytopenia. This article concludes with a concise table of clinical management questions and guidance recommendations to provide a quick reference for the practical management of heparin, low molecular weight heparin and fondaparinux

Lower Mortality with Andexanet Alfa vs 4-Factor Prothrombin Complex Concentrate for Factor Xa Inhibitor-Related Major Bleeding in a U.S. Hospital-Based Observational Study

BACKGROUND: Well-designed studies with sufficient sample size comparing andexanet alfa vs 4-factor prothrombin complex concentrate (4F-PCC) in routine clinical practice to evaluate clinical outcomes are limited. OBJECTIVES: To compare in-hospital mortality in patients hospitalized with rivaroxaban- or apixaban-related major bleeding who were treated with andexanet alfa or 4F-PCC. METHODS: An observational cohort study (ClinicalTrials.gov identifier: NCT05548777) was conducted using electronic health records between May 2018 and September 2022 from 354 U.S. hospitals. Inclusion criteria were age ≥18 years, inpatient admission with diagnosis code D68.32 (bleeding due to extrinsic anticoagulation), a record of use of the factor Xa inhibitors rivaroxaban or apixaban, andexanet alfa or 4F-PCC treatment during index hospitalization, and a documented discharge disposition. Multivariable logistic regression on in-hospital mortality with andexanet alfa vs 4F-PCC was performed. The robustness of the results was assessed via a supportive propensity score-weighted logistic regression. RESULTS: The analysis included 4395 patients (andexanet alfa, CONCLUSION: In this large observational study, treatment with andexanet alfa in patients hospitalized with rivaroxaban- or apixaban-related major bleeds was associated with 50% lower odds of in-hospital mortality than 4F-PCC. The magnitude of the risk reduction was similar in ICH and GI bleeds

Effect of Intermediate-Dose vs Standard-Dose Prophylactic Anticoagulation on Thrombotic Events, Extracorporeal Membrane Oxygenation Treatment, or Mortality among Patients with COVID-19 Admitted to the Intensive Care Unit: The INSPIRATION Randomized Clinical Trial

Importance: Thrombotic events are commonly reported in critically ill patients with COVID-19. Limited data exist to guide the intensity of antithrombotic prophylaxis. Objective: To evaluate the effects of intermediate-dose vs standard-dose prophylactic anticoagulation among patients with COVID-19 admitted to the intensive care unit (ICU). Design, Setting, and Participants: Multicenter randomized trial with a 2 � 2 factorial design performed in 10 academic centers in Iran comparing intermediate-dose vs standard-dose prophylactic anticoagulation (first hypothesis) and statin therapy vs matching placebo (second hypothesis; not reported in this article) among adult patients admitted to the ICU with COVID-19. Patients were recruited between July 29, 2020, and November 19, 2020. The final follow-up date for the 30-day primary outcome was December 19, 2020. Interventions: Intermediate-dose (enoxaparin, 1 mg/kg daily) (n = 276) vs standard prophylactic anticoagulation (enoxaparin, 40 mg daily) (n = 286), with modification according to body weight and creatinine clearance. The assigned treatments were planned to be continued until completion of 30-day follow-up. Main Outcomes and Measures: The primary efficacy outcome was a composite of venous or arterial thrombosis, treatment with extracorporeal membrane oxygenation, or mortality within 30 days, assessed in randomized patients who met the eligibility criteria and received at least 1 dose of the assigned treatment. Prespecified safety outcomes included major bleeding according to the Bleeding Academic Research Consortium (type 3 or 5 definition), powered for noninferiority (a noninferiority margin of 1.8 based on odds ratio), and severe thrombocytopenia (platelet count <20 �103/µL). All outcomes were blindly adjudicated. Results: Among 600 randomized patients, 562 (93.7) were included in the primary analysis (median interquartile range age, 62 50-71 years; 237 42.2% women). The primary efficacy outcome occurred in 126 patients (45.7%) in the intermediate-dose group and 126 patients (44.1%) in the standard-dose prophylaxis group (absolute risk difference, 1.5% 95% CI,-6.6% to 9.8%; odds ratio, 1.06 95% CI, 0.76-1.48; P =.70). Major bleeding occurred in 7 patients (2.5%) in the intermediate-dose group and 4 patients (1.4%) in the standard-dose prophylaxis group (risk difference, 1.1% 1-sided 97.5% CI,-� to 3.4%; odds ratio, 1.83 1-sided 97.5% CI, 0.00-5.93), not meeting the noninferiority criteria (P for noninferiority >.99). Severe thrombocytopenia occurred only in patients assigned to the intermediate-dose group (6 vs 0 patients; risk difference, 2.2% 95% CI, 0.4%-3.8%; P =.01). Conclusions and Relevance: Among patients admitted to the ICU with COVID-19, intermediate-dose prophylactic anticoagulation, compared with standard-dose prophylactic anticoagulation, did not result in a significant difference in the primary outcome of a composite of adjudicated venous or arterial thrombosis, treatment with extracorporeal membrane oxygenation, or mortality within 30 days. These results do not support the routine empirical use of intermediate-dose prophylactic anticoagulation in unselected patients admitted to the ICU with COVID-19. Trial Registration: ClinicalTrials.gov Identifier: NCT04486508. © 2021 American Medical Association. All rights reserved