Apixaban and rivaroxaban anti-Xa level utilization and associated bleeding events within an academic health system

Adverse events of direct factor Xa inhibitors: a disproportionality analysis of the FAERS database

OBJECTIVES

Direct factor Xa inhibitors rivaroxaban, apixaban, and edoxaban, commonly used direct oral anticoagulant (DOAC), are widely used to prevent and treat stroke and venous thromboembolic events in patients with atrial fibrillation (AF). This study aimed to assess and compare reports of adverse events associated with rivaroxaban, apixaban, and edoxaban, including hemorrhagic and non-hemorrhagic events.

METHODS

Reporting odds ratio (ROR), proportional reporting ratio (PRR), Medications and Health Care Products Regulatory Agency (MHRA), and the information component (IC) were used to perform a risk assessment of adverse event reports in the FDA Adverse Event Reporting System (FAERS) database for the years 2018-2022.

RESULTS

Combined with disproportionality analysis in different backgrounds, the salient risks of the three-factor Xa inhibitors varied. Rivaroxaban had the most significant risk of hemorrhage, apixaban had a higher incidence and risk of death, cardiac and cerebral adverse events, and edoxaban showed a more prominent risk in the kidneys and urinary system.

CONCLUSION

Hemorrhage is a common risk with factor Xa inhibitors, with rivaroxaban being the most significant. Apixaban and edoxaban also showed significant association with non-hemorrhagic adverse events, and increased attention to non-hemorrhagic adverse events is needed in clinical use.

A Pilot Study Describing DOAC Level Results and Association With Clinical Outcomes

Purpose: Describe direct oral anticoagulant (DOAC) level ordering and interpretation practices in association with clinical outcomes at a vascular medicine clinic. Methods: This study was a retrospective, observational study including patients who had a DOAC level ordered and assessed while on DOAC therapy. The primary outcome was the proportion of DOAC levels within previously reported ranges. Secondary outcomes included thrombotic events, major and clinically relevant non-major bleeding events, and the proportion of DOAC level results which prompted a change in the therapeutic plan. Results: A total of 43 patients who had a DOAC level ordered while on DOAC therapy were included in the study. More patients were on apixaban than other DOACs, and the most common indication for anticoagulation was deep vein thrombosis (DVT) or pulmonary embolism (PE). The most common reasons for ordering DOAC levels included history of gastric bypass (n = 20) and drug-drug interactions (n = 8). Most patients on apixaban had in-range levels (n = 24) compared to out of-range levels (5 patients). More patients on rivaroxaban had a level out-of-range (n = 10) than in-range (n = 4). One patient had a DVT, resulting in hospitalization and change in DOAC therapy. Two patients had bleeding events, with 1 hospitalization and change in DOAC therapy. DOAC level results also prompted changes in therapeutic plans for 9 of the patients. Conclusion: DOAC level results did not always correlate with expected outcomes, and further research is warranted to clarify which clinical situations may benefit from ordering DOAC levels.

Evaluation of Apixaban standard dosing in underweight patients with non-valvular atrial fibrillation: a retrospective cohort study

BACKGROUND

Recent guidelines recommend using direct oral anticoagulants (DOACs) as first-line agents in patients with non-valvular atrial fibrillation (NVAF). Research is currently investigating the use of Apixaban in underweight patients, with some results suggesting altered pharmacokinetics, decreased drug absorption, and potential overdosing in this population. This study examined the effectiveness and safety of standard Apixaban dosing in adult patients with atrial NVAF weighing less than 50 kg.

METHODS

This is a retrospective cohort study conducted at King Abdulaziz Medical City (KAMC); adult patients with a body mass index (BMI) below 25 who received a standard dose of Apixaban (5 mg twice daily) were categorized into two sub-cohorts based on their weight at the time of Apixaban initiation. Underweight was defined as patients weighing ≤ 50 kg, while the control group (Normal weight) comprised patients weighing > 50 kg. We followed the patients for at least one year after Apixaban initiation. The study's primary outcome was the incidence of stroke events, while secondary outcomes included bleeding (major or minor), thrombosis, and venous thromboembolism (VTE). Propensity score (PS) matching with a 1:1 ratio was used based on predefined criteria and regression model was utilized as appropriate.

RESULTS

A total of 1,433 patients were screened; of those, 277 were included according to the eligibility criteria. The incidence of stroke events was lower in the underweight than in the normal weight group at crude analysis (0% vs. 9.1%) p-value = 0.06), as well in regression analysis (OR (95%CI): 0.08 (0.001, 0.76), p-value = 0.002). On the other hand, there were no statistically significant differences between the two groups in the odds of major and minor bleeding (OR (95%CI): 0.39 (0.07, 2.03), p-value = 0.26 and OR (95%CI): 1.27 (0.56, 2.84), p-value = 0.40, respectively).

CONCLUSION

This exploratory study revealed that underweight patients with NVAF who received standard doses of Apixaban had fewer stroke events compared to normal-weight patients, without statistically significant differences in bleeding events. To confirm these findings, further randomized controlled trials with larger sample sizes and longer observation durations are required.

Clot time ratio (CTR) and relation to treatment outcome in patients with atrial fibrillation treated with Rivaroxaban

BACKGROUND

There are situations where information about the anticoagulant effects of Rivaroxaban could be clinically useful. Methods for measuring Rivaroxaban concentrations are not available at all medical laboratories while the test MRX PT DOAC for measuring the functional effects of Rivaroxaban, in CTR (Clot Time Ratio), can be made available around the clock. The objectives of this study were to investigate CTR in trough and peak samples during Rivaroxaban treatment of atrial fibrillation and to correlate the findings to bleeding episodes.

METHODS

3 trough- and 3 peak samples from 60 patients (30 on 20 mg daily and 30 on 15 mg daily) were analyzed with PT DOAC. Patients were monitored for 20 months, and bleeding and thrombotic events were documented. Descriptive statistics were used to summarize the data and non-parametric t-test for comparison between groups. ROC curves for the prediction of DOAC plasma levels > 50 ng/mL as determined with LC-MS/MS and anti-FXa methods were computed.

RESULTS

There was a significant difference between trough and peak CTR (median CTR 1.33 vs. 3.57, p < 0.001). 28 patients suffered bleeds. Patients on 20 mg Rivaroxaban with bleeds had higher mean peak CTR than patients without bleeds (CTR 4.11 vs. CTR 3.47, p = 0.040). There was no significant difference in mean CTR between patients on 15 mg Rivaroxaban with or without bleeds (CTR 3.81 vs. 3.21, p = 0.803), or when considering all patients (CTR 3.63 vs. 3.56, p = 0.445). Five out of seven patients on Rivaroxaban 20 with mean peak CTR above the dose specific first to third quartile range (Q1-Q3) suffered bleeds, while 7/16 patients with mean peak CTR within, and 1/7 patients with mean peak CTR below the Q1-Q3 suffered bleeds. The area under the ROC curve was > 0.98 at the upper limit of the PT DOAC reference interval and the negative predictive value of PT DOAC for the prediction of DOAC plasma levels > 50 ng/mL was > 0.96.

CONCLUSIONS

The sample size was too low to draw any firm conclusions but is seems that MRX PT DOAC might be a useful laboratory test in situations where the effect of Rivaroxaban needs evaluation.

Challenges to Laboratory Monitoring of Direct Oral Anticoagulants

Direct oral anticoagulants (DOACs) exert anticoagulation effect by directly inhibiting Factor Xa (rivaroxaban, apixaban, and edoxaban) or thrombin (dabigatran). Though DOACs are characterized by fixed-dose prescribing and generally do not require routine laboratory drug-level monitoring (DLM), circumstances may arise where the DLM may aid in clinical decision-making, including DOAC dose adjustment, anticoagulant class change, or decisions to withhold or administer reversal agents. We review the current literature that describes high-risk patient groups in which DLM may be beneficial for improved patient anticoagulation management and stewardship. The review also summarizes the limitations of conventional coagulation testing and discuss the emerging utility of quantitative methods for routine and rapid emergent evaluation of DOAC drug levels-in particular, the Anti-Xa activity to detect Factor Xa Inhibitors (rivaroxaban, apixaban, and edoxaban). Both technical and regulatory barriers to widespread DLM implementation are limiting factors to further clinical research that must be overcome, in order to propose universal DOAC DLM strategies and provide clinical-laboratory correlation to formally classify high-risk patient groups.

Pharmacokinetics and pharmacodynamics of direct oral anticoagulants

INTRODUCTION

Direct oral anticoagulants (DOACs) have overtaken vitamin K antagonists to become the most widely used method of anticoagulation for most indications. Their stable and predictable pharmacokinetics combined with relatively simple dosing, and the absence of routine monitoring has made them an attractive proposition for healthcare providers. Despite the benefits of DOACs as a class, important differences exist between individual DOAC drugs in respect of their pharmacokinetic and pharmacodynamic profiles with implications for dosing and reversal in cases of major bleeding.

AREAS COVERED

This review summarizes the state of knowledge relating to the pharmacokinetics of dabigatran (factor IIa/thrombin inhibitor) and apixaban, edoxaban and rivaroxaban (factor Xa) inhibitors. We focus on pharmacokinetic differences between the drugs which may have clinically significant implications.

EXPERT OPINION

Patient-centered care necessitates a careful consideration of the pharmacokinetic and pharmacodynamic differences between DOACs, and how these relate to individual patient circumstances. Prescribers should be aware of the potential for pharmacokinetic drug interactions with DOACs which may influence prescribing decisions in patients with multiple comorbidities. In order to give an appropriate dose of DOAC drugs, accurate estimation of renal function using the Cockcroft-Gault formula using actual body weight is necessary. An increasing body of evidence supports the use of DOACs in patients who are obese, and this is becoming more routine in clinical practice.

Anti-coagulant Treatment of Cancer-Associated Thrombosis in Frail Patients: Impact of Frailties on the Management of Drug-Drug Interactions

Low molecular weight heparins (LMWH) and anti-Xa direct oral anti-coagulants (DOACs) are recommended for the long-term treatment of cancer-associated thrombosis (CAT) based on well-documented randomised controlled trials. Anti-Xa DOACs are viewed as a first choice for the treatment of patients with CAT. A large number of drug-drug interactions have been reported between DOACs and chemotherapy drugs, modifying circulating levels of DOAC leading to fears of increased bleeding risks or thrombotic recurrence. Progresses in anti-neoplastic therapies have improved the prognosis and the survival, thus increasing the prevalence of frail patients with cancer. However, since frailties tend to be excluded from large trials due to multiple co-morbidities, current guidelines are not fully applicable to this population. The management of these frail patients with CAT is particularly complex and requires a risk assessment on a case-by-case basis with specific focus on cancer, patient-related risk factors and drug-drug interactions. In this brief review we have identified age, co-morbidities and co-medications as key factors of frailty that require careful attention and we have developed a therapeutic decision algorithm to help clinicians optimising the use of anti-coagulants in patients with cancer with CAT, especially in case of anti-Xa DOACs concomitant medications. With the evaluation of the bleeding risk according to the type of cancer, and anticipating drug-drug interactions intensity, taking into account patient frailties allows the optimisation of the anti-coagulant choice. A systematic collaboration between oncologists, vascular pathology specialists and pharmacists is warranted to ensure an optimal patient management. Clinical studies are needed to determine the real impact of these interactions.

Acute and chronic venous occlusion

This review article provides an overview of acute and chronic venous occlusion, a condition that can cause significant morbidity and mortality if not diagnosed and treated promptly. The article begins with an introduction to the anatomy of the venous system, followed by a discussion of the causes and clinical features of venous occlusion. The diagnostic tools available for the assessment of venous occlusion, including imaging modalities such as ultrasound, CT, and MRI, are then discussed, along with their respective advantages and limitations. The article also covers the treatment options for acute and chronic venous occlusion, including anticoagulant therapy and endovascular interventions. This review aims to provide radiologists with an updated understanding of the pathophysiology, diagnosis, and management of acute and chronic venous occlusion.

In vitro effects of Gla-domainless factor Xa analog on procoagulant and fibrinolytic pathways in apixaban-treated plasma and whole blood

BACKGROUND

Andexanet alfa is a Gla-domainless FXa (GDXa) analog used as an antidote to FXa inhibitors. Despite its clinical use, laboratory monitoring for anti-Xa reversal and the effect of andexanet on fibrinolysis has not been explored. We used a GDXa with a serine-to-alanine mutation at position 195 (chymotrypsin numbering) to model the interaction between andexanet and apixaban.

METHODS

Six batches of pooled plasma, and whole blood from healthy volunteers were treated with increasing concentrations of apixaban with/without GDXa. Thrombin generation and plasmin generation (TG and PG) were tested in plasma, and whole blood thrombus formation was tested using thromboelastometry or a flow-chamber system. FXa was also tested in isolation for its ability to support plasmin activation with/without apixaban and GDXa.

RESULTS

Apixaban (250-800 nM) concentration-dependently decreased the velocity and peak of TG in plasma. Apixaban prolonged the onset of thrombus formation in thromboelastometry and flow-chamber tests. GDXa normalized apixaban-induced delays in TG and whole blood thrombus formation. However, GDXa minimally affected the low PG velocity and peak caused by apixaban at higher concentrations (500-800 nM). FXa promoted plasmin generation independent of fibrin that was inhibited by apixaban at supratherapeutic concentrations.

CONCLUSIONS

This study demonstrated the feasibility of assessing coagulation lag time recovery in plasma and whole blood following in vitro apixaban reversal using GDXa, a biosimilar to andexanet. In contrast, GDXa-induced changes in plasmin generation and fibrinolysis were limited in PG and tPA-added ROTEM assays, supporting the endogenous profibrinolytic activity of FXa and its inhibition at elevated apixaban concentrations.

The Effectiveness and Safety of Direct Oral Anticoagulants in Obese Patients With Atrial Fibrillation: A Network Meta-Analysis

Atrial fibrillation (AF) is a cardiac condition characterized by an irregular heart rhythm, which is increasingly prevalent in the modern era. All international guidelines strongly advise the administration of anticoagulants to individuals with AF who are at high risk of stroke. These guidelines recommend the use of direct oral anticoagulants (DOACs) over warfarin because warfarin is significantly associated with increased rates of major bleeding, numerous interactions with food and drugs, and the necessity for frequent monitoring. The aim of this study is to compare the effectiveness and safety of direct oral anticoagulants (DOACs) in obese patients with atrial fibrillation. Two authors independently conducted a comprehensive literature search using electronic databases including PubMed, CINAHL, and EMBASE from inception to June 1, 2023. The efficacy outcome assessed in this meta-analysis included the composite of stroke and systemic embolism. For safety analysis, major bleeding events were compared among the study groups. Eleven studies fulfilled all the inclusion criteria and were included in the present meta-analysis enrolling 144,502 patients. In this study, DOACs demonstrate superior efficacy in preventing stroke/systemic embolism compared to warfarin. Among the DOACs, apixaban emerged as the most effective, followed by rivaroxaban, warfarin, and dabigatran. In terms of safety, apixaban was also found to be the most favorable treatment option, followed by rivaroxaban, dabigatran, and warfarin. In summary, our study concludes that apixaban exhibited greater effectiveness and safety when compared to other DOACs and warfarin in obese patients with AF.

Direct oral anticoagulants or vitamin K antagonists in emergencies: comparison of management in an observational study

Background

Restoring hemostasis in patients on oral anticoagulants presenting with major hemorrhage (MH) or before surgical intervention has changed, with the replacement of vitamin K antagonist (VKA) with direct oral anticoagulants (DOACs).

Objectives

To observe the difference in urgent hemostatic management between patients on VKA and those on DOACs.

Methods

A multicenter observational study evaluated the variation in laboratory testing, hemostatic management, mortality, and hospital length of stay (LOS) in patients on VKA or DOACs presenting with MH or urgent hemostatic restoration.

Results

Of the 1194 patients analyzed, 783 had MH (61% VKA) and 411 required urgent hemostatic restoration before surgery (56% VKA). Compared to the international normalized ratio (97.6%), plasma DOAC levels were measured less frequently (<45%), and the time taken from admission for the coagulation sample to reach the laboratory varied widely (median, 52.3 minutes; IQR, 24.8-206.7). No significant plasma DOAC level (<50 ng/mL) was found in up to 19% of patients. There was a poor relationship between plasma DOAC level and the usage of a hemostatic agent. When compared with patients receiving VKA (96.5%) or dabigatran (93.7%), fewer patients prescribed a factor Xa inhibitor (75.5%) received a prohemostatic reversal agent. The overall 30-day mortality for MH (mean: 17.8%) and length of stay (LOS) (median: 8.7 days) was similar between VKA and DOAC patients.

Conclusion

In DOAC patients, when compared to those receiving VKA, plasma DOAC levels were measured less frequently than the international normalized ratio and had a poor relationship with administering a hemostatic reversal agent. In addition, following MH, mortality and LOS were similar between VKA and DOAC patients.

Thrombin generation in real life bleeding patients on oral anticoagulants reversed (or not) with (activated) prothrombin complex concentrate

BACKGROUND

Bleeding during oral anticoagulant therapy is currently codified by expert guidelines. Monitoring of coagulation during bleeding events is challenging. Our study sought to assess thrombin generation assay (TGA) in direct oral anticoagulant-treated patients without bleeding (WB), bleeding without reversal therapy (BR-), and bleeding with reversal therapy (BR+).

METHODS

We conducted a prospective, monocentric study from June 2015 to June 2018. For all bleeding groups, TGA was evaluated using platelet-poor plasma collected upon arrival at emergency (T0), and 30 min (T1), 6 h (T2) and 24 h (T3) after reversal therapy (if indicated) following activation by tissue factor 5 pM and phospholipids.

RESULTS

Overall, 292 patients participated, including 91 BR+, 94 BR-, and 107 WB patients. At T0, vitamin K antagonist reversed (VKA-BR+) patients experienced a significant decrease in TGA parameters (ETP and peak) compared with VKA without bleeding (VKA-WB). Compared with healthy controls, VKA-BR+ patients reversed by four-factor prothrombin complex concentrate (4F-PCC) displayed comparable TGA 's ETP and peak at T1, T2, and T3, whereas direct anti-Xa BR+ patients reversed by 4F-PCC or activated prothrombin complex concentrate (aPCC) reached thrombin generation parameters that exceeded normal range at T2 and T3.

CONCLUSIONS

In VKA-treated patients reversed by 4F-PCC, TGA parameters were normalized, whereas in rivaroxaban or apixaban-treated patients reversed by 4F-PCC or aPCC, TGA parameters exceeded normal range. Further studies are needed to compare the efficacy and safety of a different dose of reversal therapy and the impact on coagulation parameters.

Comparison of the efficacy and safety of rivaroxaban and low-molecular-weight heparin in Chinese lung cancer patients with nonhigh-risk pulmonary embolism

BACKGROUND

Data that guide selection of differing anticoagulant regimens for specific cancer-associated venous thromboembolism (VTE) are lacking. We aimed to compare the efficacy and safety of rivaroxaban and low-molecular-weight heparin (LMWH) against nonhigh-risk pulmonary embolism (PE) in Chinese lung cancer patients.

METHODS

Four hundred forty-six Chinese lung cancer patients with nonhigh-risk PE who initiated treatment with rivaroxaban or LMWH were identified from Zhongshan Hospital database from 2016 to 2020. The primary outcomes were the composite event of VTE recurrence or major bleeding, and all-cause mortality. The secondary outcomes were VTE recurrence, major bleeding and clinically relevant non-major bleeding (CRNMB). Propensity score matching was used to balance baseline covariates. We conducted sensitivity analysis by stabilized inverse probability of treatment weighting and competing risk analysis by a Fine and Gray subdistribution hazard model.

RESULTS

In propensity score-matched cohorts, rivaroxaban was similar to LMWH in the risks of the composite outcome (hazard ratio (HR), 0.73; 95% confidence interval (CI), 0.45-1.21; P = 0.22), VTE recurrence (HR, 0.69; 95% CI, 0.36-1.34; P = 0.28), major bleeding (HR, 0.79; 95% CI, 0.37-1.68; P = 0.54) and CRNMB (HR, 1.13; 95% CI, 0.62-2.09; P = 0.69). All-cause mortality was significantly lower in rivaroxaban group than LMWH group (HR, 0.52; 95% CI, 0.36-0.75; P < 0.001). The primary and secondary outcomes favored rivaroxaban over LMWH in all the subgroups expect for central PE and intermediate-risk PE. The sensitivity analysis yielded similar results, and competing risk analysis was in accordance with the primary findings.

CONCLUSIONS

Rivaroxaban might be a promising alternative to LMWH as initial treatment for nonhigh-risk PE in lung cancer patients.

Descriptive analysis evaluating the use of direct oral anticoagulation therapy in heart and lung transplant recipients

BACKGROUND

Direct oral anticoagulants (DOACs) are widely utilized following cardiothoracic transplantation with limited guidance regarding drug-drug interactions (DDIs), periprocedural management, and DOAC-specific monitoring.

METHODS

We performed a single-center, retrospective, descriptive analysis of adult cardiothoracic transplant recipients initiated on DOAC therapy between May 2016 and July 2021. The primary endpoint for this analysis was the percentage of patients dosed per package labeling. Secondary endpoints included DOAC prescribing in the context of DDIs, renal dysfunction, and periprocedural management, as well as thromboembolism and major bleeding at 12 months.

RESULTS

A total of 125 patients were included in this analysis with a median age of 62 years. At initiation, 63.2% of patients were dosed according to package labeling. The most common reason for non-labeled dosing was concomitant azole antifungal therapy. DOAC therapy was held for 82 procedures with no reported thrombotic events and one major bleed in the setting of AKI. Hemodialysis-dependence was associated with a reduced risk of thrombosis (0 vs. 10 events per 100 PY, p = .002) and an increased risk of major bleeding (23 vs. 8 events per 100 PY, p = .006). Additionally, DOAC-specific anti-xa guided dosing was associated with a reduced risk of major bleeding (0 vs. 13 events per 100 PY, p < .001).

CONCLUSION

Our findings show that deviation from package labeling is common following cardiothoracic transplantation and its association with clinical outcomes warrants further study.

Apixaban and Rivaroxaban Anti-Xa Concentration Utilization in Clinical Practice

ABSTRACT

Drug-specific anti-Xa concentrations can be used to assess the presence of drug effects; however, there is inadequate guidance for clinicians on the interpretation and clinical application of these results. The purpose of this study is to review patients' first apixaban and rivaroxaban anti-Xa concentrations to identify indications for monitoring and common therapeutic interventions made based on the results. In addition, we compared bleeding and thrombotic outcomes between the obesity group body mass index ≥40 kg/m 2 and the standard group body mass index 25-39.9 kg/m 2 . A retrospective analysis was conducted at a large academic medical center from January 1, 2020, to December 31, 2020. Primary outcomes were indications for anti-Xa concentrations and interventions on results. A total of 180 patients were included in the analysis, with 119 patients (66%) in the apixaban group and 61 patients (34%) in the rivaroxaban group. The most common indications for anti-Xa concentrations were extreme body weight (23%) and concern for bleeding (22%). About half of the anti-Xa concentrations resulted in therapy changes including holding for procedure, switching to heparin or enoxaparin, holding for an elevated anti-Xa concentration or concern for bleeding, adjusting direct-acting oral anticoagulant dose, or switching to an alternative oral anticoagulant. There were no differences in bleeding complications (5% [2] vs. 16% [14], P = 0.11) or thrombotic complications (8% [3] vs. 9% [8], P = 0.85) between the obesity group and the standard group. Despite the lack of validation of therapeutic ranges for anti-Xa concentrations, this study showed clinical situations where anti-Xa concentration monitoring can be of value.

Population Pharmacokinetics and Dose Optimization Based on Renal Function of Rivaroxaban in Thai Patients with Non-Valvular Atrial Fibrillation

Low-dose rivaroxaban has been used in Asian patients with direct oral anticoagulants (DOACs) eligible for atrial fibrillation (AF). However, there are few pharmacokinetic (PK) data in Thai patients to support precise dosing. This study aimed to develop a population PK model and determine the optimal rivaroxaban doses in Thai patients. A total of 240 Anti-Xa levels of rivaroxaban from 60 Thai patients were analyzed. A population PK model was established using the nonlinear mixed-effect modeling approach. Monte Carlo simulations were used to predict drug exposures at a steady state for various dosages. Proportions of patients having rivaroxaban exposure within typical exposure ranges were determined. A one-compartment model with first-order absorption best described the data. Creatinine clearance (CrCl) and body weight significantly affected CL/F and V/F, respectively. Regardless of body weight, a higher proportion of patients with CrCl < 50 mL/min receiving the 10-mg once-daily dose had rivaroxaban exposures within the typical exposure ranges. In contrast, a higher proportion of patients with CrCl ≥ 50 mL/min receiving the 15-mg once-daily dose had rivaroxaban exposures within the typical exposure ranges. The study’s findings suggested that low-dose rivaroxaban would be better suited for Thai patients and suggested adjusting the medication’s dose in accordance with renal function.

Do Apixaban Plasma Levels Relate to Bleeding? The Clinical Outcomes and Predictive Factors for Bleeding in Patients with Non-Valvular Atrial Fibrillation

Apixaban can significantly prevent stroke events in patients with non-valvular atrial fibrillation (NVAF), as can be observed from the large, randomized, controlled trial conducted in the present study. However, the real-world evidence of bleeding events related to the apixaban plasma levels in Asian populations is limited. This study aimed to investigate the apixaban plasma levels and clinical outcomes among NVAF patients receiving apixaban, including determining the risk factors associated with bleeding during routine care. Seventy-one patients were included in the study. The median values were 112.79 (5–95th percentiles: 68.69–207.8) μg/L and 185.62 (5–95th percentiles: 124.06–384.34) μg/L for the apixaban trough (C_trough) and apixaban peak plasma levels (C_peak), respectively. Stroke and bleeding were found in 8 (11.27%) and 14 patients (19.72%), respectively. There was no statistical significance for C_trough and C_peak in the stroke and non-stroke groups, respectively. The median of C_trough (139.15 μg/L) in patients with bleeding was higher than that in the non-bleeding group (108.14 μg/L), but there was no statistical significance. However, multivariate analyses showed that bleeding history (odds ratio (OR): 17.62; 95% confidence interval (CI): 3.54–176.64; and p-value = 0.002) and C_trough (OR: 1.01; 95%: CI 1.00–1.03; and p-value = 0.038) were related to bleeding events. Almost all of the patients presented apixaban plasma levels within the expected range. Interestingly, bleeding events were associated with the troughs of the apixaban plasma levels and bleeding history.

A Combined Pharmacometrics Analysis of Biomarker Distribution Under Treatment With Standard- or Low-Dose Rivaroxaban in Real-World Chinese Patients With Nonvalvular Atrial Fibrillation

Background: The rivaroxaban dose regimen for patients with nonvalvular atrial fibrillation (NVAF) is complex in Asia. Given the high interindividual variability and the risk of bleeding caused by rivaroxaban in Asians, the influencing factors and the relationship between outlier biomarkers and bleeding events need exploration.

Methods: The integrated pharmacokinetics (PK)/pharmacodynamics (PD) models were characterized based on rich PK/PD data from 304 healthy volunteers and sparse PD [anti-factor Xa activity (anti-Xa) and prothrombin (PT)] data from 223 patients with NVAF. The correlations between PD biomarkers and clinically relevant bleedings in 1 year were explored. The final integrated PK/PD model was used to evaluate the influence of dosage and individual covariates on PD parameters.

Results: A two-compartment, linear model with sequential zero-order and first-order absorption was adopted. The dose-specific relative bioavailability (F₁), diet status, creatinine clearance, and body mass index (BMI) improved the model fit. The apparent systemic clearance was 7.39 L/h, and the central and peripheral volumes were 10.9 and 50.9 L, respectively. The linear direct-effects model with shape factor plus the additive (and/or proportional) error model described the correlation between anti-Xa/PT and plasma concentration. Bodyweight, total cholesterol (TCHO), and diet status were selected as the covariates of the anti-Xa/PT model. Anti-Xa was more sensitive to the increase in rivaroxaban exposure compared with PT. An elevated bleeding tendency was seen with higher peak anti-Xa and PT. For a typical Chinese patient, the peak anti-Xa value (median (5%–95% PI)) of 20 and 15 mg were 309 ng/ml (139–597 ng/ml) and 296 ng/ml (138–604 ng/ml), both median values were within the expected range. For patients with CrCL 30–49 ml/min, the median peak anti-Xa with recommended 10 mg other than 15 mg were within the expected range.

Conclusion: Fixed doses of rivaroxaban could be prescribed for patients with NVAF without adjustment for bodyweight, BMI, and TCHO. Randomized studies should be performed to evaluate the efficacy and safety of low-dose rivaroxaban in Chinese patients with NVAF.

Evaluation of Xa inhibitors as potential inhibitors of the SARS-CoV-2 Mpro protease

Based on previous large-scale in silico screening several factor Xa inhibitors were proposed to potentially inhibit SARS-CoV-2 Mpro. In addition to their known anticoagulants activity this potential inhibition could have an additional therapeutic effect on patients with COVID-19 disease. In this study we examined the binding of the Apixaban, Betrixaban and Rivaroxaban to the SARS-CoV-2 Mpro with the use of the MicroScale Thermophoresis technique. Our results indicate that the experimentally measured binding affinity is weak and the therapeutic effect due to the SARS-CoV-2 Mpro inhibition is rather negligible.

Apixaban and Rivaroxaban Anti-Xa Level Monitoring Versus Standard Monitoring in Hospitalized Patients With Acute Kidney Injury

BACKGROUND

Oral direct factor Xa inhibitors (FxaIs) are renally eliminated; thus, acute kidney injury (AKI) may increase the risk for drug accumulation and bleeding. There is minimal data describing the effects of AKI on FxaI anti-Xa levels or clinical outcomes.

OBJECTIVE

To compare anti-Xa level monitoring with standard monitoring in patients who experience AKI on apixaban or rivaroxaban.

METHODS

This retrospective study included patients admitted within a large hospital system from May 2016 to October 2020. Patients were included if they received apixaban or rivaroxaban prior to AKI. Patients were stratified into 1 of 2 groups: those with anti-Xa level monitoring or those who received standard monitoring. The primary outcome was major bleeding as defined by the International Society of Thrombosis and Haemostasis.

RESULTS

A total of 196 patients were included in the final analysis. Major bleeding occurred in 2 patients who received anti-Xa level monitoring, compared with 14 patients who received standard monitoring (2.1% vs 14%; P < 0.01). Variables identified as predictors of major bleeding included a documented history of liver disease (adjusted odds ratio = 3.17; 95% CI = 1.04-9.67; P = 0.04) and antiplatelet use (adjusted odds ratio = 4.18; 95% CI = 1.28-13.7; P = 0.02).

CONCLUSION AND RELEVANCE

This is the first study to demonstrate that anti-Xa level monitoring was associated with a significant reduction in major bleeding compared with standard monitoring in patients with AKI who received apixaban or rivaroxaban. The optimal management of antithrombotic medications in patients with AKI and recent exposure to an FxaI requires further investigation.

Apixaban and rivaroxaban anti-Xa level utilization for guidance of administration of andexanet alfa: a case series

BACKGROUND

Andexanet alfa, a modified recombinant factor Xa (FXa), was FDA approved in 2018 for anticoagulant reversal in patients with life-threatening bleeding associated with FXa inhibitors (FXaI). The ANNEXA-4 investigators administered andexanet alfa to patients within an 18-h from last dose of oral FXaI. In practice, time from last dose is often unknown. Previous studies have shown that clearance of these agents may be impaired by renal and hepatic dysfunction, as well as drug-drug interactions. Decision for use of andexanet alfa is also complicated by its high cost, limited drug availability, and thrombotic risk. This study aimed to describe the utility of anti-Xa DOAC levels as a decision point to administer andexanet alfa.

METHODS

This is a case series of four patients with an anti-Xa DOAC level that received andexanet alfa for oral FXaI reversal in the setting of life-threatening bleeding or prior to procedure.

RESULTS

Four patients were included in the study. Two patients had a known time since last dose of oral FXaI. All patients had a detectable anti-Xa DOAC levels prior to administration of andexanet alfa. Two patients had levels within the peak range, one patient had a level below the peak range, and one patient had a level above the peak range. Andexanet alfa was administered after anti-Xa DOAC level return in all patients.

CONCLUSION

In our case series, obtaining anti-Xa DOAC levels prior to administration of andexanet alfa was achievable and facilitated use of reversal agents in patients with major bleeding or emergent procedural need.

Critical Analysis of Apixaban Dose Adjustment Criteria

Apixaban is indicated for the prevention of ischemic stroke in non-valvular atrial fibrillation (NVAF), as well as for the prevention and treatment of venous thromboembolism (VTE). Dose adjustment is based on age, weight, and serum creatinine in NVAF, while there are no recommended adjustment criteria for VTE. Such adjustment is unconventional compared to other commonly used medications. The objective of this manuscript is to critically analyze each apixaban dosing adjustment criterion and its associated outcomes. PubMed articles from March 2013 to March 2020 were selected with search terms “apixaban,” and “dose adjustment,” “adjustment,” or “adjustment criteria.” Pharmacokinetic studies demonstrated increased apixaban exposure in patients >65 years of age, those with extreme body weights, and those with advanced renal impairment, though post-hemodialysis dosing may off-set the elevated apixaban exposure. However, clinical data show that among patients >75 years, <60 kg, and with estimated glomerular filtration rate <50 mL/min, including those on dialysis, there is no reduction in apixaban safety or efficacy. Published literature describes variable dosing strategies utilized in clinical practice. Overall, apixaban dose adjustment criteria may need to be re-evaluated.