Real-World Rivaroxaban and Apixaban Levels in Asian Patients With Atrial Fibrillation

Impact of cerebral small vessel disease burden and drug level at admission on direct oral anticoagulant associated intracerebral hemorrhage

INTRODUCTION

Direct oral anticoagulant (DOAC)-associated intracerebral hemorrhage (ICH) is a catastrophic complication. The aim of this study was to investigate the association between computed tomography (CT)-based cerebrovascular small vessel disease (SVD) burden and DOAC-ICH as well as the DOAC concentration upon hospital admission and ICH outcome.

PATIENTS AND METHODS

The study included two cohorts: (1) DOAC-ICH: patients who suffered from DOAC-ICH and underwent drug level measurements upon admission; (2) DOAC-non-ICH: stable DOAC users who underwent head CT without ICH during treatment. We categorized the DOAC levels of the DOAC-ICH patients as low (<50 ng/mL), medium (50-300 ng/mL), and high (>300 ng/mL). The CT-based SVD burden (including white matter lesions [WML], lacunes, and cerebral atrophy) was evaluated, and SVD scores (range, 0-3) were used to evaluate SVD severity.

RESULTS

A total of 43 DOAC-ICH patients and 177 DOAC-non-ICH patients were enrolled. DOAC-ICH patients were more likely to have WML, lacunes, or cerebral atrophy compared to DOAC-non-ICH patients. After adjustment, the SVD burden was associated with DOAC-ICH, with a higher risk of more severe SVD (SVD score of 2; odds ratio [OR], 10.3 [3.17, 33.3]; score of 3; OR, 16.8 [4.50, 62.6]). The proportions of patients with high, medium, and low drug levels in the DOAC-ICH group were 16.3%, 55.8%, and 27.9%, respectively. Additionally, the high-level group displayed a larger hematoma size and had worse functional outcomes at 3 months than the other two groups.

DISCUSSION AND CONCLUSION

The severity of SVD burden was associated with DOAC-ICH. Furthermore, high DOAC levels in ICH were associated with unfavorable clinical outcomes. To address the potential selection bias from these two cohorts, a prospective study to investigate the co-contribution of drug levels and SVD to DOAC-ICH is essential.

Comparisons of effectiveness and safety between on-label dosing, off-label underdosing, and off-label overdosing in Asian and non-Asian atrial fibrillation patients treated with rivaroxaban: a systematic review and meta-analysis of observational studies

AIMS

Limited real-world data show that rivaroxaban following dosage criteria from either ROCKET AF [20 mg/day or 15 mg/day if creatinine clearance (CrCl) < 50 mL/min] or J-ROCKET AF (15 mg/day or 10 mg/day if CrCl < 50 mL/min) is associated with comparable risks of thromboembolism and bleeding with each other in patients with non-valvular atrial fibrillation (NVAF). We are aimed to study whether these observations differ between Asian and non-Asian subjects.

METHODS AND RESULTS

A systematic review and meta-analysis with random effects was conducted to estimate the aggregate hazard ratio (HR) and 95% confidence interval (CI) using PubMed and MEDLINE databases from 8 September 2011 to 31 December 2022 searched for adjusted observational studies that reported relevant clinical outcomes of NVAF patients receiving rivaroxaban 10 mg/day if CrCl > 50 mL/min, on-label dose rivaroxaban eligible for ROCKET AF or J-ROCKET AF, and rivaroxaban 20 mg/day if CrCl < 50 mL/min. Effectiveness and safety endpoints were compared between ROCKET AF and J-ROCKET AF dosing regimen in Asian and non-Asian subjects, separately. Also, risks of events of rivaroxaban 10 mg/day despite of CrCl > 50 mL/min and rivaroxaban 20 mg/day despite of CrCl < 50 mL/min were compared to that of 'ROCKET AF/J-ROCKET AF dosing'. Sensitivity analyses were performed by sequential elimination of each study from the pool. The meta-regression analysis was performed to explore the influence of potential factors on the effectiveness and safety outcomes. Eighteen studies involving 67 571 Asian and 54 882 non-Asian patients were included. Rivaroxaban following J-ROCKET AF criteria was associated with comparable risks of thromboembolism in the Asian subgroup, whereas rivaroxaban following J-ROCKET AF criteria was associated with higher risks of all-cause mortality (HR:1.30; 95% CI:1.05-1.60) compared with that of ROCKET AF criteria in the non-Asian population. There were no differences in risks of major bleeding between rivaroxaban following J-ROCKET AF vs. ROCKET AF criteria either in the Asian or non-Asian population. The use of rivaroxaban 10 mg despite of CrCl > 50 mL/min was associated with a higher risk of thromboembolism (HR:1.64; 95% CI:1.28-2.11) but lower risk of major bleeding (HR:0.72; 95% CI:0.57-0.90) compared with eligible dosage criteria. The use of rivaroxaban 20 mg despite of CrCl < 50 mL/min was associated with worse clinical outcomes in the risks of thromboembolism (HR:1.32; 95% CI:1.09-1.59), mortality (HR:1.33; 95% CI:1.10-1.59), and major bleeding (HR:1.26; 95% CI:1.03-1.53) compared with eligible dosage criteria. The pooled results were generally in line with the primary effectiveness and safety outcomes by removing a single study at one time. Meta-regression analyses failed to detect the bias in most potential patient characteristics associated with the clinical outcomes.

CONCLUSION

Rivaroxaban dosing regimen following J-ROCKET criteria may serve as an alternative to ROCKET AF criteria for the Asian population with NVAF, whereas the dosing regimen following ROCKET AF criteria was more favourable for the non-Asian population. The use of rivaroxaban 10 mg despite of CrCl > 50 mL/min was associated with a higher risk of thromboembolism but a lower risk of major bleeding, while use of rivaroxaban 20 mg despite of CrCl < 50 mL/min was associated with worse outcome in most clinical events.

Simvastatin, but Not Atorvastatin, Is Associated with Higher Peak Rivaroxaban Serum Levels and Bleeding: an Asian Cohort Study from Singapore

AIMS

This study attempts to identify predictors associated with bleeding and stroke and systemic embolism (SSE) in Singaporean Asians taking rivaroxaban and apixaban.

METHODS

A total of 134 Singaporean patients on either rivaroxaban or apixaban for non-valvular atrial fibrillation were included for this study. Baseline characteristics were recorded at recruitment while bleeding and SSE events were recorded during a 1-year follow-up. Peak and trough drug plasma concentrations were collected based on the dosing interval and pharmacokinetics of the drugs and quantified using high performance liquid chromatography. Characteristics of patients with or without bleeds were compared using relevant statistical tests. Multivariable regression that included covariates with p < 0.1 from an initial univariable regression was performed to analyse predictors that resulted in higher risk of bleeding in patients.

RESULTS

Median creatinine clearance (CrCl) was significantly lower in patients on rivaroxaban who experienced bleeds as compared to patients who did not experience bleeds (61.5 vs 70.8 mL/min, p = 0.047), while concomitant simvastatin use was found to be independently associated with a sixfold increased risk of bleeding (adjusted OR = 6.14 (95% CI: 1.18-31.97), p = 0.031) for rivaroxaban after controlling for body mass index, CrCl and having experienced a previous SSE.

CONCLUSION

Our findings suggest that concomitant use of simvastatin with rivaroxaban may be associated with bleeding events in an Asian cohort. Further studies using physiologically based pharmacokinetic modelling are required to investigate the drug-drug interactions between these drugs.

The association between direct oral anticoagulant concentration upon acute stroke and stroke outcome

BACKGROUND

This study aimed to investigate the association between direct oral anticoagulant (DOAC) concentration upon acute ischemic stroke (IS) or intracranial hemorrhage (ICH) and stroke outcomes.

METHODS

Patients aged ≥20 years treated with DOACs, including dabigatran, rivaroxaban, apixaban, or edoxaban, and developed acute IS or ICH were enrolled to measure DOAC concentration at the time of hospital presentation by using ultrahigh-performance liquid chromatography with tandem mass spectrometry. Ischemic stroke patients was categorized into low (<50 ng/mL) and effective (≥50 ng/mL) groups. The primary outcome was poor functional outcomes at 3 months (modified Rankin Scale scores of 4-6).

RESULTS

A total of 138 patients were enrolled, including 105 IS (76.1%) and 33 ICH patients. In the IS cohort, the average DOAC concentration was 85.7 ± 88.6 ng/mL (low DOAC concentration: 42.9%). Low level group had numerically higher NIHSS (14 versus 9, p = 0.37), significantly poorer functional outcomes at 3 months (odds ratio [OR], 5.08 [1.32, 19.63]), and higher chance of stroke-in-evolution (OR, 6.83 [1.64, 28.41]). In the ICH cohort, the average DOAC concentration was 128.9 ± 111.9 ng/mL. Reversal therapy was administered in 60.6% of patients. Hematoma growth occurred in 35.7% patients. The DOAC concentration was similar across patients with or without reversal therapy, and with or without hematoma growth.

CONCLUSION

Among DOAC users who developed IS, low drug concentrations at hospital presentation predicted poor outcomes.

Drug-drug interactions with direct oral anticoagulants for the prevention of ischemic stroke and embolism in atrial fibrillation: a narrative review of adverse events

INTRODUCTION

In randomized trials, direct oral anticoagulants (DOAC) were non-inferior to the vitamin-K-antagonist (VKA) warfarin in preventing stroke/embolism in patients with atrial fibrillation (AF). DOAC are substrates for P-glycoprotein (P-gp), CYP3A4 and CYP2C9. The activity of these enzymes is modulated by several drugs which might induce pharmacokinetic drug-drug interactions (DDI). Drugs affecting platelet function have the potential for pharmacodynamic DDI of DOAC.

AREAS COVERED

The literature was searched for: 'dabigatran,' 'rivaroxaban,' 'edoxaban,' or 'apixaban' and drugs affecting platelet function, CYP3A4-, CYP2C9- or P-gp-activity. Reports about bleeding and embolic events attributed to DDI with DOAC in AF-patients were found for 43 of 171 drugs with interacting potential (25%), most frequently with antiplatelet and nonsteroidal anti-inflammatory drugs. Whereas a co-medication of platelet-affecting drugs is invariably reported to increase the bleeding risk, the findings regarding P-gp-, CYP3A4- and CYP2C9- activity-affecting drugs are ambiguous.

EXPERT OPINION

Tests for plasma DOAC-levels and information about DDI of DOAC should be widely available and user-friendly. If advantages and disadvantages of DOAC and VKA can be investigated exhaustively, individualized anticoagulant therapy can be offered to patients, considering co-medication, comorbidities, genetic and geographic factors and the health care system.

Insights into the Pharmacokinetics and Pharmacodynamics of Direct Oral Anticoagulants in Older Adults with Atrial Fibrillation: A Structured Narrative Review

Older adults, the fastest growing population, represent almost 50% of all users of direct oral anticoagulants (DOACs). Unfortunately, we have very little relevant pharmacological and clinical data on DOACs, especially in older adults with geriatric profiles. This is highly relevant as pharmacokinetics and pharmacodynamics (PK/PD) often differ substantially in this population. Hence, we need to obtain a better understanding of the PK/PD of DOACs in older adults, to ensure appropriate treatment. This review summarises the current insights into PK/PD of DOACs in older adults. A search was undertaken up to October 2022 to identify PK/PD studies of apixaban, dabigatran, edoxaban, and rivaroxaban, that included older adults aged ≥ 75 years. This review identified 44 articles. Older age alone did not influence exposure of edoxaban, rivaroxaban and dabigatran, while apixaban peak concentrations were 40% higher in older adults than in young volunteers. Nevertheless, high interindividual variability in DOAC exposure in older adults was noted, which can be explained by distinctive older patient characteristics, such as kidney function, changes in body composition (especially reduced muscle mass), and co-medication with P-gp inhibitors, which is in line with the current dosing reduction criteria of apixaban, edoxaban, and rivaroxaban. Dabigatran had the largest interindividual variability among all DOACs since its dose adjustment criterion is only age, and thus it is not a preferable option. Additionally, DOAC exposure, which fell outside of on-therapy ranges, was significantly related to stroke and bleeding events. No definite thresholds linked to these outcomes in older adults have been established.

TAVR: nemesis of NOACs?

Data on non-vitamin K antagonist oral anticoagulants (NOACs) in transcatheter aortic valve replacement (TAVR) patients are controversial. In patients without atrial fibrillation (AF), rivaroxaban showed enhanced ischemia and bleeding as compared to standard of care. ENVISAGE showed enhanced bleeding in AF patients as compared to vitamin K antagonist (VKA). Only apixaban was non-inferior but failed superiority regarding bleeding in AF patients after TAVR. One could hypothesize that this might be due to pharmacokinetics of NOACs. Therefore, we compared outcome in rivaroxaban/edoxaban (once-daily) and apixaban (twice-daily) treated patients. 568 patients with indication for permanent oral anticoagulation due to AF undergoing TAVR were analyzed via inverse probability of treatment weighting. Valve academic research consortium complications during 30-day follow-up were assessed. Bleeding complications were similar in once-daily and twice-daily NOACs (major: 22 (7.5%) vs. 14 (5.3%), p = 0.285; minor: 66 (22.4%) vs. 46 (17.4%), p = 0.133). Complications did not change when splitting the cohort in the different agents apixaban, rivaroxaban and edoxaban. These findings remained robust after multivariate analysis. In summary, twice-daily and once-daily NOACs did not differ regarding bleeding complications in a hypothesis generating real-world cohort of TAVR patients with AF.

Plasma apixaban levels in Chinese patients with chronic kidney disease-Relationship with renal function and bleeding complications

Introduction: Accumulation of apixaban in plasma is a major concern in patients with chronic kidney disease (CKD). Studies that investigated plasma apixaban level in CKD patients and its association with clinically significant events are scarce. Methods: Patients with CKD Stage 1-4 who were taking apixaban, either 2.5 mg BD or 5 mg BD were recruited. The peak and trough plasma apixaban level were measured after 2 h and 12 h of last dose respectively. The results were correlated with renal function and clinical events during the period of follow-up from 1 January 2018 to 31 October 2021. Results: 141 patients (CKD Stage 1, n = 12; Stage 2, n = 74; Stage 3, n = 48, stage 4, n = 7) were included for analysis. The plasma peak and trough apixaban were significantly higher in patients with CKD stage 3 when compared with those having CKD stage 2 and 1 (peak levels: 223.4 ± 107.8 ng/ml vs. 161.0 ± 55.2 ng/ml vs. 126.6 ± 30.2 ng/ml; trough levels: 118.3 ± 67.9 ng/ml vs. 81.2 ± 33.0 ng/ml vs. 51.9 ± 31.1 ng/ml, p < 0.05 or all) in patients taking 5 mg BD. Plasma trough apixaban level was negatively correlated with eGFR in patients taking 5 mg BD (r ² = -0.174, p < 0.001) and 2.5 mg BD (r ² = -0.215, p < 0.05). The plasma peak and trough apixaban level correlated with PT (r ² = 0.065, p = 0.003 and r ² = 0.096, p < 0.01 respectively). Multivariate analysis showed that plasma trough apixaban levels were associated with the risk of bleeding complications (Odd ratio: 1.011, 95% CI:1.002-1.021, p = 0.023). Conclusion: The plasma apixaban level shows a trend of increase with worsening renal function, and an increase in the plasma apixaban level is suggestive of an increased risk of bleeding complications in patients with CKD. Further large-scale prospective studies are needed to evaluate relationship between plasma apixaban level and renal function as well as safety outcome in CKD patients. Moreover, the role of drug level monitoring should be prospectively evaluated for dosage optimization and the minimization of bleeding risks in CKD patients.

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.

Plasma Rivaroxaban Level in Patients With Early Stages of Chronic Kidney Disease-Relationships With Renal Function and Clinical Events

Introduction Drug accumulation of rivaroxaban is a concern in patients with chronic kidney disease (CKD). Data regarding the plasma rivaroxaban levels in early CKD patients and its relationship with clinical events is lacking. Methods Early CKD patients (Stage 1-3) with atrial fibrillation who received rivaroxaban (15 or 20 mg daily) were recruited. Plasma rivaroxaban levels were measured at 2 hours (peak) and 24 hours (trough) after drug administration, and correlated with eGFR and clinically significant events during the follow-up period (1 January 2018 to 31 October 2021). Results Ninety-two patients were included (CKD stage 1 n=10, stage 2 n=53, stage 3 n=29). Plasma trough levels in patients with stage 3 CKD were significantly higher than those with stage 2 and 1 CKD (66.0±34.9 ng/ml vs. 35.7 ± 24.7 ng/ml vs. 34.7 ± 26.2 ng/ml, respectively, p=0.005), and showed inverse relationship with eGFR (r=0.391, p=0.001) in patients receiving 20 mg daily. The plasma trough rivaroxaban level correlated with PT and APTT (r = 0.650 and 0.44, respectively, p<0.001 for both). Plasma trough rivaroxaban level in those with bleeding were higher than those who did not (59.9 ± 35.6 ng/ml vs. 41.1 ± 29.2 ng/ml, p=0.011), and multivariate analysis suggested that plasma trough rivaroxaban level was associated with the rate of bleeding complications (OR: 1.020, 95% CI 1.002-1.038, p=0.028). Conclusion Plasma trough rivaroxaban levels correlated with renal function in early CKD patients, and its measurement may help dosage optimization in patients with renal impairment. Moreover, our data suggests that there may be an association between plasma trough rivaroxaban level and the rate of bleeding complication.

Oral anticoagulants vs antiplatelets in cryptogenic stroke with potential cardiac emboli: Meta-analysis

BACKGROUND

The best antithrombotic strategy for cryptogenic stroke with potential cardiac emboli is not known. The objective of this study was to conduct a meta-analysis to evaluate the efficacy and safety of oral anticoagulants (OACs) vs. antiplatelet therapies in these patients METHODS: Pubmed, EMBASE, CENTRAL and clinicaltrials.gov were searched from January 1980 to April 2021 to identify trials comparing OACs versus antiplatelet therapies in patients with cryptogenic stroke and potential cardiac emboli (patent foramen ovale, moderate-severe left atrial enlargement, heart failure with reduced ejection fraction). Relative risk (RR) with 95% confidence (CI) was used as a measure of the effect of OACs versus antiplatelet therapies on recurrent ischemic stroke and major bleeding. We computed a random-effect estimate based on the Mantel-Haenszel method for a given outcome.

RESULTS

We identified 6 studies derived from 5 trials with 2282 patients. Pooled results from 6 studies showed that compared with antiplatelet therapies, OACs were associated with a lower risk of recurrent ischemic stroke (RR 0.61, 95% CI 0.41 to 0.91, P=0.02). Only 3 studies of cryptogenic stroke with patent foramen ovale reported a major bleeding endpoint and pooled results from random-effects model showed that OACs compared with antiplatelet therapies were associated with a non-significantly increased risk of major bleeding (RR 1.61, 95% CI 0.76 to 3.40, P=0.21).

CONCLUSIONS

OACs compared with antiplatelet therapies were associated with a reduced recurrent ischemic stroke risk and OACs might be a viable non-procedural alternative in patients with cryptogenic stroke and potential cardiac emboli.

Impact of different renal function equations on direct oral anticoagulant concentrations

The purpose of this study is to investigate the correlation between glomerular filtration rate (GFR) estimated by different renal function equations and non-vitamin K antagonist oral anticoagulant concentration. Atrial fibrillation patients who aged ≥ 20 years and used dabigatran, rivaroxaban, or apixaban for thromboembolism prevention were enrolled to collect blood samples and measure drug concentrations using ultra-high-performance liquid chromatography with tandem mass spectrometry. The GFR was estimated using the Cockroft–Gault formula (abbreviated as creatinine clearance, CrCL), Chronic Kidney Disease Epidemiology Collaboration formula (CKD-EPI) featuring both creatinine and cystatin C, and the Modification of Diet in Renal Disease Study equation (MDRD). Multivariate regression was used to investigate the associations of different renal function estimates with drug concentrations. A total of 511 participants were enrolled, including 146 dabigatran users, 164 rivaroxaban users and 201 apixaban users. Compared to clinical trials, 35.4% of dabigatran, 4.9% of rivaroxaban, and 5.5% of apixaban concentrations were higher than the expected range (p < 0.001). CKD-EPI and MDRD estimates classified fewer patients as having GFR < 50 mL/min than CrCL in all 3 groups. Both CrCL and CKD-EPI were associated with higher-than-expected ranges of dabigatran or rivaroxaban concentrations. Nevertheless, none of the renal function equations was associated with higher-than-expected apixaban concentrations. For participants aged ≥ 75 years, CKD-EPI may be associated with higher-than-expected trough concentration of dabigatran. In conclusion, CrCL and CKD-EPI both can be used to identify patients with high trough concentrations of dabigatran or rivaroxaban. Among elderly patients who used dabigatran, CKD-EPI may be associated with increased drug concentration.

Assessment of exposure to direct oral anticoagulants in elderly hospitalised patients

It is unclear whether elderly patients established on direct oral anticoagulants (DOACs) have greater exposure to these drugs, which could subsequently increase their risk of bleeding. We assessed DOAC exposure and factors affecting it in a real-world elderly cohort of patients. For this, 151 medically stable hospital inpatients (76 established on apixaban, 61 on rivaroxaban, 14 on dabigatran) with a median [interquartile range (IQR)] age of 84 (78-89) years were recruited. Patients provided blood samples for measurement of peak and trough plasma DOAC concentrations. There was up to 48-fold and 13-fold variation in trough and peak plasma drug concentrations respectively. A significantly greater proportion of patients on apixaban had peak plasma drug concentrations within the reported ranges compared to those on either rivaroxaban or dabigatran (82·9% vs. 44·3% vs. 64·3% respectively; P < 0·001). A third of the variability in DOAC plasma concentrations was attributed to the influences of DOAC dosage, renal function and gender. To what extent the observed increases in DOAC exposure in the older patients is the cause of their increased risk of bleeding, which could potentially be ameliorated by dosing titration, requires further investigation.

Plasma Rivaroxaban Level to Identify Patients at Risk of Drug Overexposure: Is a Single Measurement of Drug Level Reliable?

Introduction  Dose adjustment based on laboratory monitoring is not routinely recommended for patients treated with rivaroxaban but because an association has been reported between high drug level and bleeding, it would be of interest to know if measuring drug level once could identify patients at risk of bleeding who might benefit from a dose reduction.

Objective  This study was aimed to investigate the reliability of a single measurement of rivaroxaban level to identify clinic patients with persistently high levels, defined as levels that remained in the upper quintile of drug-level distribution.

Methods  In this prospective cohort study of 100 patients with atrial fibrillation or venous thromboembolism, peak and trough rivaroxaban levels were measured using the STA-Liquid Anti-Xa assay at baseline and after 2 months. Values of 395.8 and 60.2 ng/mL corresponded to the 80th percentile for peak and trough levels, respectively, and levels above these cut-offs were categorized as high for our analyses.

Results  Among patients with a peak or trough level in the upper quintile at baseline, only 26.7% (95% confidence interval [CI]: 10.9–52.0%), and 13.3% (95% CI: 2.4–37.9%), respectively, remained above these thresholds.

Conclusion  Our findings do not support the use of a single rivaroxaban level measurement to identify patients who would benefit from a dose reduction because such an approach is unable to reliably identify patients with high levels.

A Real-world Experience of the Safety and Efficacy of Non-vitamin K Oral Anticoagulants Versus Warfarin in Patients with Non-valvular Atrial Fibrillation— A Single-centre Retrospective Cohort Study in Singapore

Introduction: Non-vitamin K oral anticoagulants (NOACs) were shown to have better outcomes than warfarin for non-valvular atrial fibrillation (NVAF). Given limited local real-world data, this study aims to evaluate the safety and efficacy of NOACs versus warfarin for NVAF in Singapore. Methods: This single-centre retrospective cohort study included 439 patients ≥ 21 years old that were newly prescribed with oral anticoagulants (OACs) for NVAF in 2015. Follow-ups for patients upon OAC initiation lasted either for 2 years or until the occurrence of bleeding or thromboembolism event or death (whichever was earlier). Primary endpoints included major bleeding and stroke, while secondary endpoints included overall bleeding and thromboembolic events. Time-to-events was evaluated via Kaplan-Meier survival analysis. Data on time in therapeutic range (TTR) and compliance were analysed. Results: Patients were assigned to 4 groups: warfarin (157, 35.8%), rivaroxaban (154, 35.1%), apixaban (98, 22.3%) and dabigatran (30, 6.8%). With a mean age of 70.8 (±10.8) years old, the population were predominantly males (56.5%) and comprised Chinese (73.8%), Malays (18.7%) and others (7.5%). The rates of stroke per year were 0.7%, 1.7%, 2.2% and 0% for warfarin, rivaroxaban, apixaban and dabigatran, respectively (P=0.411), whereas those of major bleeding were 2.7%, 1.4%, 2.2% and 0% (P=0.560). As compared to warfarin, no significant differences were observed for risks of stroke and of major bleeding for rivaroxaban (adjusted hazard ratio (HR) 4.19, 95% confidence interval (CI) 0.68–26.05, P=0.124 and adjusted HR 0.43, 95% CI 0.12–1.59, P=0.207) and apixaban (adjusted HR 5.33, 95% CI 0.85–33.34, P=0.074 and adjusted HR 1.54, 95% CI 0.39–6.15, P=0.538). Mean TTR was 68.8% (±24.3%) for warfarin. Compliance rates for rivaroxaban, apixaban, and dabigatran were 56.6%, 59.2%, and 44.8% respectively (P=0.177). Conclusion: NOACs were associated with similar stroke and major bleeding rates as warfarin for NVAF. Keywords: Anticoagulant, Asian, atrial fibrillation, compliance, haemorrhage, thrombosis

Non-Vitamin K Antagonist Oral Anticoagulants and the Gastrointestinal Bleeding Risk in Real-World Studies

In the present study, we aimed to provide evidence from high-quality real world studies for a comprehensive and rigorous analysis on the gastrointestinal bleeding (GIB) risk for non-vitamin K antagonist oral anticoagulants (NOACs). We performed a systematic search of MEDLINE, EMBASE and PUBMED, and of 286 records screened, we included data from 11 high-quality real-world studies, coordinated by independent research groups over the last 3 years, that reported major GIB events in patients given NOACs or vitamin K antagonists for patients with nonvalvular atrial fibrillation. The lowest risk of gastrointestinal bleeding was with apixaban compared with warfarin (hazard ratio (HR) for GIB for apixaban ranging between 0.45 (95% confidence interval (CI) 0.34 to 0.59) and 1.13 (95% CI 0.79 to 1.63)). Apixaban was associated with a lower risk of GI bleeding than dabigatran ((HR ranging between 0.39 (95% CI 0.27 to 0.58) and 0.95 (95% CI 0.65 to 1.18)) or rivaroxaban ((HR ranging between 0.33 (95% CI 0.22 to 0.49) and 0.82 (95% CI 0.62 to 1.08)). The results of our study confirm a low or a similar risk for major GIB between patients receiving apixaban or dabigatran compared with warfarin, and apixaban appears to be associated with the lowest risk of GIB.

Interindividual Variability of Apixaban Plasma Concentrations: Influence of Clinical and Genetic Factors in a Real-Life Cohort of Atrial Fibrillation Patients

(1) Background: Prescribing apixaban for stroke prevention has significantly increased in patients with non-valvular atrial fibrillation (NVAF). The ABCB₁ genotype can influence apixaban absorption and bioavailability. The aim of the present study was to assess the factors that influence apixaban’s plasma level and to establish if a certain relationship has clinical relevance. (2) Methods: Fifty-three NVAF patients were treated with 5 mg apixaban twice/day (70.0 years, range: 65–77, 60.4% men). Trough and peak plasma concentrations of apixaban were determined by liquid chromatography-tandem mass-spectrometry (LC-MS/MS), and ABCB₁ genotyping was performed. (3) Results: Apixaban plasma concentrations varied considerably. They were higher in women than in men (311.2 ng/dL vs. 252.2 ng/dL; p = 0.05) and were lower in patients with heart failure (149.4 ng/dL vs. 304.5 ng/dL; p < 0.01). Creatinine clearance was inversely correlated with the apixaban plasma level (Spearman correlation: r = −0.365; p = 0.007 for trough concentrations). No statistically significant differences between the genotypic groups of ABCB₁ rs1045642 and ABCB₁ rs4148738 were found in the trough or peak apixaban plasma concentrations. (4) Conclusions: Pharmacokinetic parameters are influenced by several clinical factors of which renal function is the major determinant. Plasma concentrations measured in women had higher values than those measured in men, and heart failure was associated with decreased plasma levels of apixaban.