High-dose Rivaroxaban Research Articles

Rivaroxaban down-regulates pyroptosis and the TLR4/NF-κB/NLRP3 signaling pathway to promote flap survival

BackgroundFlap placement remains the primary method for wound repair, but postoperative ischemic flap necrosis is of major concern. This study explored whether rivaroxaban, a factor Xa inhibitor, enhanced flap survival. MethodsThirty-six rats were randomly divided into control, low-dose rivaroxaban (3 mg/kg/day), and high-dose rivaroxaban (7 mg/kg/day) groups. On postoperative day 7, the flap survival rate was analyzed and the average survival area calculated. After the rats were euthanized, immunological and molecular biological techniques were employed to assess vascular regeneration, pyroptosis, and inflammation. ResultsRivaroxaban upregulated VEGF expression, in turn enhancing angiogenesis, and it downregulated IL-1β, IL-6, and TNF-α expression, thereby mitigating inflammation. The drug also suppressed TLR4, NF-κB p65, NLRP3, caspase-1, and IL-18 syntheses, thus inhibiting pyroptosis. ConclusionsRivaroxaban enhanced random flap survival by down-regulating the TLR4/NF-κB/NLRP3 signaling pathway to suppress pyroptosis, promoting vascular regeneration and inhibiting inflammation.

Design and Optimization of Rivaroxaban-Cyclodextrin-Polymer Triple Complex Formulation with Improved Solubility.

This study aimed to ensure the convenience of administration and reproducibility of efficacy, regardless of the meal, by improving the solubility of rivaroxaban (RIV). RIV is a non-vitamin K antagonist oral anticoagulants that exhibits a coagulation effect by directly inhibiting coagulation factor Xa. However, RIV has a very low solubility; therefore, it must be administered with a meal at high doses. We used a drug- hydroxypropyl-beta-cyclodextrin (CD)-water-soluble polymer triple complex (R-C-P complex) to solubilize RIV. Using Minitab, we evaluated the effect of each factor on RIV solubility and developed an optimal R-C-P complex formulation. The amount of CD, amount of polymer, and polymer type were set as the independent variables X1, X2, and X3, respectively. RIV solubility (Y1) and dissolution rate for 45 min in pH 4.5 medium (Y2) and pH 1.2 medium (Y3) were set as response variables. The most efficient RIV solubilization effect was obtained from the composition using CD and HPMC 2208, and physicochemical properties and dissolution parameters were analyzed. RIV in the R-C-P complex was present in an amorphous form and showed high solubility. Unlike commercial products, it showed a 100% dissolution rate. The R-C-P complex formulation secured high RIV solubility and 100% release regardless of pH. The results imply that high-dose RIV can be administered regardless of the meal, reducing the risk of changing the drug effect due to the patient's administration mistake.

Effects of direct oral anticoagulants dabigatran and rivaroxaban on the blood coagulation function in rabbits.

The aim of this study was to explore the effects of dabigatran and rivaroxaban on the activities of various coagulation factors. To achieve that, 60 rabbits were randomly divided into experimental groups that received different doses of dabigatran or rivaroxaban. The effects of dabigatran and rivaroxaban on the activities of FII, FV, FVIII, FX, and activated protein C (APC) were analyzed. In the dabigatran groups, activated partial thromboplastin time and thromboplastin time (TT) were prolonged after drug administration, and the activities of FII, FV, FVIII, and FX were inhibited as the drug concentration increased. Low doses of dabigatran inhibited APC activity. In the rivaroxaban groups, APTT and TT were not significantly prolonged after drug administration. In contrast, the high-dose rivaroxaban group exhibited prolonged PT, and the degree of inhibition of the activities of FII, FV, FVIII, and FX increased as the drug concentration increased. Rivaroxaban had no significant effect on APC activity regardless of dosage. As the drug concentration increased, both NOACs had more significant inhibitory effects on the activities of FII, FV, FVIII, and FX. Low concentrations of dabigatran generated an inhibitory effect on APC activity, while high concentrations of dabigatran had no significant effect. Rivaroxaban had no significant effect on APC activity.

POSB201 Effectiveness and Safety of Low Versus High Dose Rivaroxaban and Apixaban for Atrial Fibrillation: Propensity Score-Matched Cohort Study

Low-dose direct oral anticoagulant (DOAC) use is more prevalent than expected in clinical practice but evidence of its effectiveness and safety compared to higher doses in patients with atrial fibrillation (AF) remains limited.

Rivaroxaban dosing in patients with atrial fibrillation: results from the RIVER registry – is dosing according to renal function appropriate?

Abstract Introduction Rivaroxaban is recommended as an option for anticoagulation in patients with nonvalvular atrial fibrillation (AF) with one or more risk factors for stroke. The approved/recommended rivaroxaban dose for stroke prevention in patients with atrial fibrillation (AF) is solely based on renal function: 20 mg once daily (od) for patients with a creatinine clearance [CrCl] ≥50 ml/min and 15 mg od in patients with CrCl 15–49 mL/min). Purpose To assess the patterns of rivaroxaban prescription as per the creatinine clearances levels and to assess the impact of the rivaroxaban dosing on the rate of events at 2-year follow-up in patients with AF. Methods RIVaroxaban Evaluation in Real Life setting (RIVER) is a prospective international registry of patients with newly diagnosed non-valvular AF treated with rivaroxaban for the prevention of thromboembolic stroke and at least one investigator-determined risk factor for stroke. Adjusted hazard ratios (HRs) were obtained through Cox proportional-hazard model. Results Among 3402 patients with normal renal function (CrCl ≥50 mL/min), 82.1% were prescribed the recommended rivaroxaban dose of 20 mg (od) at baseline. Among 524 patients with moderate or severe renal impairment (CrCl 15–50 mL/min), 55.3% patients received rivaroxaban 15 mg (od), 39.9% received 20 mg (od) and 4.2% 10 mg (od). Non-recommended dosing was rare in patients younger than 70 (13.5%) but more frequent in older patients (28.8%). Non-recommended low dosing was more frequent in Asians (38.9%), compared to non-Asian patients (13.8%). Regarding clinical outcomes, adjusted hazards ratios (HR, presented with 95% confidence intervals) showed that the non-recommended low dosing (<20 mg od) was associated with higher risk of non-cardiovascular mortality (HR 2.09 (1.16–3.77)) in patients with normal renal function. The non-recommended high dosing (>15 mg od) was associated with lower risk of all-cause mortality (HR 0.63 (0.42–0.93)) and cardiovascular mortality (HR 0.32 (0.13–0.77)) and higher risk of major bleeding (HR 2.86 (1.49–5.50)) in patients with moderate to severe renal impairment (figure 1 and 2). Conclusion In patients with normal renal function, non-recommended low dose rivaroxaban was associated with increased cardiovascular mortality without reducing the risk of major bleeding compared to recommended dosing. In patients with CrCl <50 ml/min, non-recommended high dose rivaroxaban was associated with reduced cardiovascular mortality but at the cost of increased major bleeding. These observational data largely support the reduction of rivaroxaban dosing according to renal function but educational strategies are needed to ensure that rivaroxaban is used appropriately. Funding Acknowledgement Type of funding sources: Private grant(s) and/or Sponsorship. Main funding source(s): This work was supported by an unrestricted research grant from Bayer AG, Berlin, Germany, to TRI, London, UK, which sponsors the RIVER registry. This work is supported by KANTOR CHARITABLE FOUNDATION for the Kantor-Kakkar Global Centre for Thrombosis Science.

Factor Xa inhibitor rivaroxaban suppresses experimental abdominal aortic aneurysm progression via attenuating aortic inflammation

ObjectiveRivaroxaban is a specific factor Xa (FXa) inhibitor for venous thromboembolism treatment. Recently, increasing evidence have reported the beneficial effects of rivaroxaban on treating cardiovascular disorders such as coronary and peripheral artery disease. However, its potential influence on abdominal aortic aneurysm (AAA) remains unclear. This study aims to investigate whether rivaroxaban treatment could attenuate experimental AAA progression and its related mechanisms. Approaches and resultsIn human aneurysmal aorta, FXa protein expression was significantly upregulated. Further investigations identified a positive correlation among plasma FXa level, AAA severity (the maximal aortic diameter), and intra-aneurysmal thrombus percentage. In Ang II (angiotensin II)-infused ApoE−/− mice, the administration of high dose rivaroxaban (15 mg/kg/d) for 14 days significantly reduced the maximal aortic diameter, while low dose rivaroxaban (5 mg/kg/d) did not display such a protective role. Although rivaroxaban treatments reduced the incidence of AAA and thrombus formation, these differences did not reach statistical significance. Immunohistochemistry revealed a pronounced aortic remodeling including increased collagen content and enhanced elastin degradation in Ang II-induced AAAs, which was inhibited by high dose rivaroxaban treatment. Further analysis demonstrated that rivaroxaban exerted its protective effects by decreasing leukocyte infiltration, inflammatory cytokines expression, and matrix metalloproteinases (MMPs) expression in the aortic wall. The inhibitory effect of rivaroxaban on aneurysm development was also observed in calcium chloride-induced AAA model. Mechanistically, in human aortic endothelial cells, FXa stimulation increased the expression of inflammatory cytokines (interleukin (IL)-1β, IL-6, IL-8, monocyte chemoattractant protein-1) and adhesive molecules, which were all reversed by the cotreatment of rivaroxaban. Subsequent monocyte-endothelial cell interaction was enhanced after FXa stimulation and was alleviated by rivaroxaban cotreatment. In addition, FXa induced a significantly heightened expression of MMP2 in human aortic endothelial cells, which was ameliorated by rivaroxaban coadministration. ConclusionsRivaroxaban attenuated both angiotensin II- and calcium chloride-induced abdominal aortic aneurysm (AAA) progressions, through inhibiting aortic remodeling and inflammation. Rivaroxaban could be a promising therapeutic agent in attenuating AAA development by counteracting FXa-induced aortic wall inflammation.

Non-vitamin K antagonist oral anticoagulants (NOACs) post-percutaneous coronary intervention: a network meta-analysis.

Clinicians must balance the risks of bleeding and thrombosis after percutaneous coronary intervention (PCI) in people with an indication for anticoagulation. The potential of non-vitamin K antagonists (NOACs) to prevent bleeding complications is promising, but evidence remains limited. To review the evidence from randomised controlled trials assessing the efficacy and safety of non-vitamin K antagonist oral anticoagulants (NOACs) compared to vitamin K antagonists post-percutaneous coronary intervention (PCI) in people with an indication for anticoagulation. We identified studies by searching CENTRAL, MEDLINE, Embase, the Conference Proceedings Citation Index - Science and two clinical trials registers in February 2019. We checked bibliographies of identified studies and applied no language restrictions. We searched for randomised controlled trials (RCT) that compared NOACs and vitamin K antagonists for people with an indication for anticoagulation who underwent PCI. Two review authors independently checked the results of searches to identify relevant studies, assessed each included study, and extracted study data. We conducted random-effects, pairwise analyses using Review Manager 5 and network meta-analyses (NMA) using the R package 'netmeta'. We ranked competing treatments by P scores, which are derived from the P values of all pairwise comparisons, and allow ranking of treatments on a continuous 0 to 1 scale. We identified nine RCTs that met the inclusion criteria, but four were ongoing trials, and were not included in this analysis. We included five RCTs, with 8373 participants, in the NMA (two RCTs compared apixaban to a vitamin K antagonist, two RCTs compared rivaroxaban to a vitamin K antagonist, and one RCT compared dabigatran to a vitamin K antagonist). Very low- to moderate-certainty evidence suggests little or no difference between NOACs and vitamin K antagonists in death from cardiovascular causes (not reported in the dabigatran trial), myocardial infarction, stroke, death from any cause, and stent thrombosis. Apixaban (RR 0.85, 95% CI 0.77 to 0.95), high dose rivaroxaban (RR 0.86, 95% CI 0.74 to 1.00), and low dose rivaroxaban (RR 0.80, 95% CI 0.68 to 0.92) probably reduce the risk of recurrent hospitalisation compared with vitamin K antagonists. No studies looked at health-related quality of life. Very low- to moderate-certainty evidence suggests that NOACs may be safer than vitamin K antagonists in terms of bleeding. Both high dose dabigatran (RR 0.53, 95% CI 0.29 to 0.97), and low dose dabigatran (RR 0.38, 95% CI 0.21 to 0.70) may reduce major bleeding more than vitamin K antagonists. High dose dabigatran (RR 0.83, 95% CI 0.72 to 0.96), low dose dabigatran (RR 0.66, 95% CI 0.58 to 0.75), apixaban (RR 0,67 , 95% Cl 0.51 to 0.88), high dose rivaroxaban (RR 0.66, 95% CI 0.52 to 0.83), and low dose rivaroxaban (RR 0.71, 95% CI 0.57 to 0.88) probably reduce non-major bleeding more than vitamin K antagonists. The results from the NMA were inconclusive between the different NOACs for all primary and secondary outcomes. Very low- to moderate-certainty evidence suggests no meaningful difference in efficacy outcomes between non-vitamin K antagonist oral anticoagulants (NOAC) and vitamin K antagonists following percutaneous coronary interventions (PCI) in people with non-valvular atrial fibrillation. NOACs probably reduce the risk of recurrent hospitalisation for adverse events compared with vitamin K antagonists. Low- to moderate-certainty evidence suggests that dabigatran may reduce the rates of major and non-major bleeding, and apixaban and rivaroxaban probably reduce the rates of non-major bleeding compared with vitamin K antagonists. Our network meta-analysis did not show superiority of one NOAC over another for any of the outcomes. Head to head trials, directly comparing NOACs against each other, are required to provide more certain evidence.

Management of pulmonary embolism after recent intracranial hemorrhage

Rationale:Venous thromboembolism may result from prolong immobilization following intracerebral hemorrhage. Massive pulmonary embolism with associated right heart failure is life-threatening, requiring treatment with anticoagulants or even thrombolytic agents. However, these drugs are contraindicated after a recent hemorrhagic episode, as they may induce further hemorrhage. There are no guidelines for treatment in these circumstances.Patient concerns:A 57-year-old man experienced massive pulmonary embolism and shock 18 days after an intracerebral hemorrhage.Diagnoses:Tachycardia and high D-dimer (21.27 mg/L fibrinogen-equivalent units) were noted. Chest computed tomography showed bilateral pulmonary trunk embolism.Interventions:Heparinization were used and activated partial thromboplastin time therapeutic range was 50 to 70 seconds. Fortunately, shock status and shortness of breath improved two days later. Continuing high dose Rivaroxaban was administrated for three weeks.Outcomes:There was no recurrent intracranial hemorrhage (ICH) following treatment for three-weeks with high-dose and one-year with standard dose of rivaroxaban. This report presents a treatment option in the management of these difficult clinical situations.Lessons:The combination of unfractionated heparin infusion and continuing non-Vitamin K antagonist oral anticoagulants use could manage life-threatening pulmonary embolism following recent ICH. Theoretically, the use of NOAC is a safer strategy if the patient with previous history of major ICH.

Demeanor of rivaroxaban in activated/inactivated FXa

Activated factor X (FXa) plays an important role in thrombin generation and inflammation. Factor X is not converted constitutively to FXa, but only after intrinsic clotting factors are activated and/or cellular injury occurs. Although rivaroxaban is one of direct FXa inhibitors, its function in the inactivated coagulation cascade is unclear. In human umbilical vein endothelial cells that natively express protease-activated receptor-1 and -2, high dose rivaroxaban did not alter gene transcripts including pro-inflammatory genes in DNA microarray. Upon FXa stimulation, the expressions of pro-inflammatory genes such as monocyte chemoattractant protein-1 (MCP-1), intracellular adhesion molecule-1, and interleukin-8 were maximally increased at 4 h after stimulation, and were suppressed by rivaroxaban. To confirm these results, quantitative polymerase chain reaction and enzyme-linked immunosorbent assay (ELISA) for MCP-1 were performed. FXa evoked the expression of MCP-1 maximally at 4 h after stimulation, whereas MCP-1 displayed a different temporal activation in ELISA. Interestingly, rivaroxaban inhibited both time courses of MCP-1 expression. These results suggest that rivaroxaban may not influence gene modulation in the inactivated coagulation state, but can attenuate the endothelial damage evoked by FXa and pro-inflammatory cytokine genes.

Reduction of intracerebral hemorrhage by rivaroxaban after tPA thrombolysis is associated with downregulation of PAR-1 and PAR-2.

This study aimed to assess the risk of intracerebral hemorrhage (ICH) after tissue-type plasminogen activator (tPA) treatment in rivaroxaban compared with warfarin-pretreated male Wistar rat brain after ischemia in relation to activation profiles of protease-activated receptor-1, -2, -3, and -4 (PAR-1, -2, -3, and -4). After pretreatment with warfarin (0.2 mg/kg/day), low-dose rivaroxaban (60 mg/kg/day), high-dose rivaroxaban (120 mg/kg/day), or vehicle for 14 days, transient middle cerebral artery occlusion was induced for 90 min, followed by reperfusion with tPA (10 mg/kg/10 ml). Infarct volume, hemorrhagic volume, immunoglobulin G leakage, and blood parameters were examined. Twenty-four hours after reperfusion, immunohistochemistry for PARs was performed in brain sections. ICH volume was increased in the warfarin-pretreated group compared with the rivaroxaban-treated group. PAR-1, -2, -3, and -4 were widely expressed in the normal brain, and their levels were increased in the ischemic brain, especially in the peri-ischemic lesion. Warfarin pretreatment enhanced the expression of PAR-1 and PAR-2 in the peri-ischemic lesion, whereas rivaroxaban pretreatment did not. The present study shows a lower risk of brain hemorrhage in rivaroxaban-pretreated compared with warfarin-pretreated rats following tPA administration to the ischemic brain. It is suggested that the relative downregulation of PAR-1 and PAR-2 by rivaroxaban compared with warfarin pretreatment might be partly involved in the mechanism of reduced hemorrhagic complications in patients receiving rivaroxaban in clinical trials. © 2016 Wiley Periodicals, Inc.

Rivaroxaban, a factor Xa inhibitor, induces the secondary prevention of cardiovascular events after myocardial ischemia reperfusion injury in mice

ObjectivesRivaroxaban has been shown to reduce overall death from cardiovascular causes in patients with recent acute coronary syndrome. Therefore, we evaluated the secondary prevention of cardiovascular events after myocardial ischemia reperfusion injury and its mechanisms in mice. MethodsAfter myocardial reperfusion injury, C57BL/6J mice were randomized to receive either no treatment or treatment for 14days with low and high doses of rivaroxaban. After 7days, mice were administered tissue factor as a secondary event. ResultsBased on a Kaplan–Meier curve analysis, the high-dose rivaroxaban group showed a significantly higher % survival than the no-treatment group from day 7 (after the administration of tissue factor) to day 14 (at the end of the experimental period). Left ventricular (LV) ejection fraction in both the low- and high-dose rivaroxaban groups improved compared to that in the no-treatment group. Moreover, mRNA levels of interleukin-6 and collagens 1α2 and 3α1 in the LV in the high-dose group were significantly suppressed compared to those in the no-treatment group. ConclusionsRivaroxaban improved the survival rate, probably by improving cardiac function through the reduction of inflammatory and fibrotic factors in the LV. This effect may be due to the pleiotropic effects of rivaroxaban beyond its main effect as an anti-coagulant.

Effects of Pretreatment with Warfarin or Rivaroxaban on Neurovascular Unit Dissociation after Tissue Plasminogen Activator Thrombolysis in Ischemic Rat Brain

Warfarin and rivaroxaban are highly effective in reducing stroke risk in patients with atrial fibrillation (AF). However, their effects on anticoagulation and neurovascular unit (NVU) change remain elusive. In this study, we assessed the risks and benefits of pre-treatment with warfarin or rivaroxaban after tissue-type plasminogen activator (tPA) thrombolysis in ischemic rat brain. Pre-treatment with warfarin (.2 mg/kg/day), low dose rivaroxaban (60 mg/kg/day), high dose rivaroxaban (120 mg/kg/day) or vehicle was performed for 2 weeks, transient middle cerebral artery occlusion (tMCAO) was induced for 90 min, then followed by reperfusion with tPA. At 24 hours (h) after reperfusion, we observed the changes of matrix metalloproteinase-9 (MMP-9), tissue factor, caspase 3 and NVU dissociation. Prothrombin time (PT) was significantly prolonged in the warfarin and rivaroxaban pretreated groups. MMP-9 expression greatly increased in the warfarin group, and this was reduced in the rivaroxaban groups compared with the vehicle group. Tissue factor expression remarkably decreased in the warfarin and rivaroxaban groups. The number of caspase 3-positive cells had no difference among all the groups. Marked dissociations between astrocyte foot processes and the basal lamina or pericytes were observed in the warfarin pretreated group, but such dissociations were improved in the rivaroxaban groups. Our present study shows that pre-treatment with rivaroxaban was noninferior to warfarin in the anticoagulation, but a lower risk of NVU dysfunction and dissociation after tPA treatment in rivaroxaban. This finding could partly explain the mechanism of reducing hemorrhagic complications by rivaroxaban in clinical studies.

Rivaroxaban, a factor Xa inhibitor, improves neovascularization in the ischemic hindlimb of streptozotocin-induced diabetic mice.

BackgroundFactor Xa inhibitor is used for preventing venous thromboembolism (VTE) in adult patients receiving orthopedic operation. However, the role of factor Xa inhibitor, rivaroxaban, in angiogenesis is still unknown.Methods and resultsStreptozotocin (STZ)–induced diabetic mice with model of hind-limb ischemia, were divided into non-diabetic control, diabetic control, and low- and high-dose rivaroxaban treatment groups, in order to evaluate the effect of rivaroxaban in angiogenesis. Doppler perfusion imaging showed that blood flow recovery was significantly increased, and more capillary density occurred in the rivaroxaban treatment group. In vitro studies, human endothelial progenitor cells (EPCs) treated with rivaroxaban had significant functional improvement in migration and senescence under hyperglycemic conditions. Rivaroxaban also increased endothelial nitric oxide synthase (eNOS) as well as vascular endothelial growth factor (VEGF) expressions in hyperglycemia-stimulated EPCs.ConclusionsRivaroxaban promoted vessel formation in diabetic mice and improved endothelial progenitor cell function under hyperglycemic conditions. These effects may be associated with enhancement of expression of eNOS and VEGF.

Reversal of rivaroxaban anticoagulation by haemostatic agents in rats and primates

Rivaroxaban is an oral, direct factor Xa inhibitor for the management of thromboembolic disorders. Despite its short half-life, the ability to reverse rivaroxaban anticoagulation could be beneficial in life-threatening emergencies. The potential of prothrombin complex concentrate (PCC; Beriplex®), activated PCC (aPCC; FEIBA®) or recombinant activated factor VII (rFVIIa; NovoSeven®) to reverse rivaroxaban in rats and baboons was investigated. Anaesthetised rats pre-treated with intravenous rivaroxaban (2mg/kg) received intravenous rFVIIa (100/400μg/kg), PCC (25/50 U/kg) or aPCC (50/100U/kg) after initiation of bleeding. Clotting times and bleeding times (BTs) were recorded. Rivaroxaban was administered as an intravenous 0.6mg/kg bolus followed by continuous 0.6 mg/kg/hour infusion in baboons. Animals received intravenous aPCC 50U/kg (2U/kg/minute) or rFVIIa 210 μg/kg. BT and clotting parameters were measured. In rats pretreated with high-dose rivaroxaban, PCC 50 U/kg, aPCC 100 U/kg and rFVIIa 400μg/kg significantly reduced BT vs rivaroxaban alone (5.4 ± 1.4-fold to 1.5 ± 0.4-fold [p<0.05]; 3.0 ± 0.4-fold to 1.4 ± 0.1-fold [p<0.001]; and 3.5 ± 0.7-fold to 1.7 ± 0.2-fold [p<0.01] vs baseline, respectively). In baboons pre-infused with rivaroxaban and then given aPCC, BT increased by 2.0 ± 0.2-fold and aPCC returned BT to baseline for the duration of its infusion. rFVIIa reduced BT from 2.5 ± 0.3-fold over baseline to 1.7 ± 0.3-fold over baseline. Prolongation of prothrombin time was reduced by PCC, aPCC and rFVIIa in both species. Rivaroxaban reduced thrombin-antithrombin levels; application of PCC and aPCC, but not rFVIIa, increased these levels. In conclusion, PCC, aPCC or rFVIIa have the potential to reverse the anticoagulant and anti-haemostatic effects of rivaroxaban.

Comparison of unfractionated heparin, low-molecular-weight heparin, low-dose and high-dose rivaroxaban in preventing thrombus formation on mechanical heart valves: results of an in vitro study

Thromboembolism and bleeding after mechanical heart valve replacement are still unsolved problems, particularly for patients requiring anticoagulative bridging therapy. The aim of this study was to investigate whether rivaroxaban, a new oral selective and direct coagulation factor Xa inhibitor, is as effective as enoxaparin and unfractionated heparin (UFH) in preventing thrombus formation on mechanical heart valves using an in vitro system. Blood from healthy male donors was anticoagulated with either UFH, enoxaparin, rivaroxaban at 300ng/ml, (n=10 each), or rivaroxaban at 30ng/ml (n=3). Mechanical aortic valve prostheses were placed into the in vitro testing system THIA II and exposed to the anticoagulant blood mixtures at a pulsatile flow for 60min. Overall thrombus weight, coagulation parameters, and electron microscopic features of thrombus formation on the valve surface were quantified as endpoints. The mean thrombus weights were 163±64mg for group 1 (UFH), 341±63mg for the group 2 (enoxaparin), 238±83mg for group 3 (rivaroxaban 300ng/ml) and 1.739±16mg for group 4 (rivaroxaban 30ng/ml). Whereas high-dosed rivaroxaban showed no significant differences compared to UFH or enoxaparin, low-dosed rivaroxaban generated a massive thrombus generation, thus differing significantly from all other treatment groups regarding the thrombus weight. We hypothesize that high-dose rivaroxaban is a competitive oral available alternative to UFH and LMWH's, that might be a worthwhile alternative for patients in need of anticoagulative bridging therapy. Prospective studies have to evaluate if rivaroxaban might even overcome the limitations of OAC in patients after implantation of artificial heart valves.

Potential of Activated Prothrombin Complex Concentrate and Activated Factor VII to Reverse the Anticoagulant Effects of Rivaroxaban in Primates

Rivaroxaban is an oral, direct Factor Xa (FXa) inhibitor that has been recommended for approval by the Committee for Medicinal Products for Human Use for the prevention of venous thromboembolism after elective hip and knee replacement, and is in advanced clinical development for the prevention and treatment of thromboembolic disorders. Because bleeding is a potential side-effect of accidental rivaroxaban overdose, we evaluated whether activated prothrombin complex concentrate (APCC, FEIBA®) and recombinant activated Factor VII (rFVIIa, NovoSeven®) administration could mitigate the antihemostatic effects of high-dose rivaroxaban in juvenile male baboons. Pharmacologic impairment of hemostasis (3- to 4-fold increase in prothrombin time [PT] from baseline and ≥2-fold increase in template bleeding time [BT]) was achieved by an intravenous (i.v.) bolus of rivaroxaban (0.6 mg/kg) followed by continuous infusion (0.6 mg/kg/h) for 60 minutes. At steady-state anticoagulation (30 minutes from bolus), one group of anticoagulated baboons (n=7) received APCC (50 U/kg, over 25 minutes). A second group (n=7) received an i.v. bolus dose of rFVIIa (210 μg/kg) 30 minutes after the start of anticoagulation. Reversal of the antihemostatic effects of supratherapeutic doses of rivaroxaban by APCC and rFVIIa was assessed by measurement of BT and clotting times. In the APCC group, high-dose rivaroxaban prolonged BT to 202% (95% CI±21%; p<0.001) of baseline and PT by 3-fold (Table). On completion of APCC infusion, BT returned to baseline and PT was reduced. In the rFVIIa group, rivaroxaban prolonged BT to 254% (95% CI±30%; p<0.05). Infusion of rFVIIa reduced BT by 34%, and PT was also shortened. Circulating thrombin–antithrombin complex (TAT) levels decreased during rivaroxaban infusion, and this decrease did not change significantly after rFVIIa bolus administration. However, APCC increased baseline plasma TAT levels, suggesting a systemic hypercoagulation. We conclude that administration of APCC or rVIIa can rapidly attenuate hemostasis impairment after rivaroxaban overdose in baboons, thus providing potential antidotes during bleeding emergencies.Table. The effect of activated prothrombin complex concentrate (APCC) and recombinant activated Factor VII (rFVIIa) on bleeding time (BT), prothrombin time (PT), and thrombin–antithrombin complex concentration (TAT) in baboons anticoagulated with high-dose rivaroxaban (n=7 each). Values are given as mean ± standard deviationTimeBT (x-fold change from baseline)PT (x-fold change from baseline)TAT (μg/L)APCCBaseline1.001.003.51±0.0830 minutes after rivaroxaban2.02±0.563.04±0.433.01±1.37At end of APCC infusion1.02±0.332.20±0.2910.35±1.4120 minutes after end of APCC infusion1.65±0.942.28±0.29n.d.rFVIIaBaseline1.001.007.35±4.1730 minutes after rivaroxaban2.54±0.793.17±0.422.95±0.795 minutes after rFVIIa1.68±0.802.38±0.412.58±0.5230 minutes after rFVIIa1.96±1.262.48±0.494.00±1.12

Partial Reversal of the Anticoagulant Effect of High-Dose Rivaroxaban - An Oral, Direct Factor Xa Inhibitor - by Recombinant Factor VIIa in Rats.

Rivaroxaban (BAY 59-7939) is a novel, oral, direct Factor Xa (FXa) inhibitor in advanced clinical development for the prevention and treatment of thromboembolic disorders. The antithrombotic activity of rivaroxaban has been demonstrated in several venous and arterial thrombosis models in rats, at doses that did not increase bleeding times. However, as with all anticoagulants, high doses of rivaroxaban cause prolongation of bleeding time. The aim of this study was to assess the ability of recombinant Factor VIIa (rFVIIa, NovoSeven®) to neutralize the anticoagulant effects of high-dose rivaroxaban. Animals were divided into four study groups receiving the following treatment and the appropriate placebo: rivaroxaban 2 mg/kg, rivaroxaban 2 mg/kg plus rFVIIa 100 or 400 μg/kg i.v, and rFVIIa 400 μg/kg i.v. Anesthetized rats were pretreated with rivaroxaban (or placebo); rFVIIa (or placebo) was then injected intravenously 1 minute after induction of bleeding. Mesenteric bleeding times were measured after cutting small branched arteries using microsurgery scissors, while the intestinal surface was superfused with 0.9% NaCl solution. Bleeding times were obtained from three control vessel incisions before treatment, and one after intravenous administration of rivaroxaban and/or rFVIIa (n=10). Prothrombin time (PT), thrombin generation (TG), and inhibition of FXa activity (activated by Russell's viper venom) were measured in blood from animals that had received study medication (rivaroxaban 2 mg/kg and/or rFVIIa 400 μg/kg) or placebo, but had not been used for bleeding time determination (n=6). Administration of rFVIIa (400 μg/kg) reduced mesenteric bleeding time to 0.7-times baseline (Table). High-dose rivaroxaban increased bleeding time to 3.3-times baseline. The administration of rFVIIa to animals which had received rivaroxaban significantly reduced the bleeding times to 2.4- and 1.7-times baseline at doses of 100 μg/kg and 400 μg/kg, respectively. Administration of rFVIIa (400 μg/kg) reduced PT and the lag time of TG, but had no effect on endogenous thrombin potential (ETP: total amount of thrombin activity) in control animals. Rivaroxaban-induced prolongation of PT and lag time of TG were partially reversed by rFVIIa, as was the reduction in ETP. Rivaroxaban-induced inhibition of FXa activity was not affected by rFVIIa. These results demonstrate that rFVIIa partially reverses the anticoagulation effect (bleeding time, prolongation of PT, ETP, and lag time of TG) of rivaroxaban without affecting inhibition of FXa activity. Thus, these data indicate that rFVIIa has the potential to be used as an antidote to the oral, direct FXa inhibitor, rivaroxaban, if this was necessary.GroupChange in bleeding time (x-fold)PT (sec)Thrombin generation (ETP) (nM x min)Thrombin generation lag time (min)Inhibition of FXa activity (%)Placebo1 (baseline)15±0.4516±161.2 ±0.040±3rFVIIa 400 μg/kg0.7±0.17±0.2507±190.7±0.011±4Rivaroxaban 2 mg/kg3.3±0.597±5.6363±142.4±0.277±4Rivaroxaban 2 mg/kg + rFVIIa 400 μg/kg1.7±0.254±3.5428±131.9±0.181±2ETP: endogenous thrombin potential