Rivaroxaban and Post-Stroke Neurological Outcomes in Patients With Acute Coronary Syndrome

Thrombin as target for prevention of recurrent events after acute coronary syndromes

The mechanism underlying thrombus formation in acute coronary syndrome (ACS) involves both platelets and thrombin. While both pathways are targeted in acute care, platelet inhibition has been predominantly administered in the chronic phase, yet thrombin plays a key role in platelet activation and fibrin formation. Among ACS patients, there is also a persistent chronic increase in thrombin generation, which is associated with a higher rate of adverse events. In the setting of post-ACS care with rivaroxaban or vorapaxar, targeting thrombin has been associated with decreased thrombin generation and reduced cardiovascular events, but has been associated with increased bleeding risk. We explored the evidence supporting thrombin generation in the pathophysiology of recurrent events post-ACS and the role of thrombin as a viable therapeutic target. One specific target is factor XI inhibition, which is involved in thrombin generation, but may also allow for the preservation of normal hemostasis.

Risks of Stroke and Mortality in Atrial Fibrillation Patients Treated With Rivaroxaban and Warfarin

Background and Purpose- Oral anticoagulation therapy is standard of care for patients with nonvalvular atrial fibrillation to prevent stroke. This study compared rivaroxaban and warfarin for stroke and all-cause mortality risk reduction in a real-world setting. Methods- This retrospective cohort study (2011-2017) included de-identified patients from the Optum Clinformatics Database who started treatment with rivaroxaban or warfarin within 30 days following initial diagnosis of nonvalvular atrial fibrillation. Before nonvalvular atrial fibrillation diagnosis, patients had 6 months of continuous health plan enrollment and CHA₂DS₂-VASc score ≥2. Stroke severity was determined by the National Institutes of Health Stroke Scale, imputed based on machine learning algorithms. Stroke and all-cause mortality risks were compared by treatment using Cox proportional hazard regression, with inverse probability of treatment weighting to balance cohorts for baseline risk factors. Stratified analysis by treatment duration was also performed. Results- During a mean follow-up of 27 months, 175 (1.33/100 patient-years [PY]) rivaroxaban-treated and 536 (1.66/100 PY) warfarin-treated patients developed stroke. The inverse probability of treatment weighting model showed that rivaroxaban reduced stroke risk by 19% (hazard ratio [HR], 0.81 [95% CI, 0.73-0.91]). Analysis by stroke severity revealed risk reductions by rivaroxaban of 48% for severe stroke (National Institutes of Health Stroke Scale score, 16-42; HR, 0.52 [95% CI, 0.33-0.82]) and 19% for minor stroke (National Institutes of Health Stroke Scale score, 1 to <5; HR, 0.81 [95% CI, 0.68-0.96]), but no difference for moderate stroke (National Institutes of Health Stroke Scale score, 5 to <16; HR, 0.93 [95% CI, 0.78-1.10]). A total of 41 (0.31/100 PY) rivaroxaban-treated and 147 (0.44/100 PY) warfarin-treated patients died poststroke, 12 (0.09/100 PY) and 67 (0.20/100 PY) of whom died within 30 days, representing mortality risk reductions by rivaroxaban of 24% (HR, 0.76 [95% CI, 0.61-0.95]) poststroke and 59% (HR, 0.41 [95% CI, 0.28-0.60]) within 30 days. Conclusions- After the initial diagnosis of atrial fibrillation, patients treated with rivaroxaban versus warfarin had significant risk reduction for stroke, especially severe stroke, and all-cause mortality after a stroke. Findings from this observational study may help inform anticoagulant choice for stroke prevention in patients with nonvalvular atrial fibrillation.

Simultaneous Determination of Rivaroxaban and Enalapril in Rat Plasma by UPLC-MS/MS and Its Application to A Pharmacokinetic Interaction Study

BACKGROUND AND OBJECTIVES

There have been no animal experiments and clinical studies on the pharmacokinetic interaction between rivaroxaban and enalapril. To investigate whether a potential pharmacokinetic interaction is present between rivaroxaban and enalapril, a rapid and sensitive Ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) method was developed and validated to determine the concentration of rivaroxaban and enalapril in rat plasma and was then applied to a pharmacokinetic interaction study.

METHODS

The analytes were separated on an Acquity UPLC BEH C18 chromatography column (2.1 × 50 mm, 1.7 μm) with acetonitrile and 0.1% formic acid as the mobile phase with gradient elution. The mass spectrometer was operated in multiple reaction monitoring mode to monitor the precursor-to-product ion transitions of 436.1 → 145.1 m/z for rivaroxaban, 377.3 → 234.2 m/z for enalapril and 285.2 → 193.1 m/z for diazepam (IS).

RESULTS

The method was validated over the concentration range of 1.0-200 ng/mL for rivaroxaban and 0.5-100 ng/mL for enalapril. The intra- and inter-day precision and accuracy of the quality control (QC) samples exhibited relative standard deviations (RSD) < 9.4% and the accuracy values ranged from - 8.3 to 9.6%. After co-administration of rivaroxaban and enalapril, the maximum plasma concentration (C_max) and area under the systemic drug concentration-time curve from time 0 to infinity (AUC_0-∞) of rivaroxaban were significantly increased by 19.6% (p < 0.05) and 21.3% (p < 0.05), respectively. On the contrary, the plasma clearance rate (CL/F) of rivaroxaban and enalapril was significantly decreased by 17.8% (p < 0.05) and 23.8% (p < 0.05), respectively.

CONCLUSIONS

The UPLC-MS/MS method was successfully applied to simultaneous determination of rivaroxaban and enalapril in rat plasma and applied to study the pharmacokinetic interaction between rivaroxaban and enalapril. The co-administration of rivaroxaban and enalapril resulted in a significant drug interaction in rats.