Rivaroxaban-loaded SLNs with treatment potential of deep vein thrombosis: in-vitro, in-vivo, and toxicity evaluation.

OBJECTIVES: Rivaroxaban (RXB), a novel Xa inhibitor having groundbreaking therapeutic potential. However, this drug is associated with few limitations, including its pharmacokinetics related toxicities. Here, we developed RXB-loaded SLNs (RXB-SLNs) to improve its biopharmaceutical profile. Methods: High pressure homogenizer was used to prepare RXB-SLNs, followed by their particle characterization, Transmission electron microscopy (TEM), Dynamic light scattering (DSC), and Powder X-ray diffraction (PXRD) analysis. Beside this, in-vitro, ex-vivo, and in-vivo evaluation, prothrombin time assessment and toxicity was investigated. RESULTS: RXB-SLNs had their particle size in nano range (99.1 ± 5.50 nm) with excellent morphology and low polydispersity index (0.402 ± 0.02) and suitable zeta potential (-25.9 ± 1.4 mV). The incorporation efficiency was observed around 95.9 ± 3.9%. In-vitro release profiles of the RXB-SLNs exhibited enhanced dissolution (89 ± 9.91%) as compared to pure drug (11 ± 1.43%) after 24 h of the study. PK study demonstrated a seven times enhanced bioavailability of RXB-SLNs when compared with pure drug. Furthermore, RXB-SLNs exhibited an expressive anti-coagulant behavior in human and rat blood plasma. Also, the final formulation exhibited no toxicity after oral administration of the SLNs. CONCLUSIONS: All together, these studies revealed the capability of the SLNs for carrying the RXB with enhanced therapeutic efficacy and no toxicity, most importantly for the treatment of deep vein thrombosis.

Reversing Rivaroxaban Anticoagulation as Part of a Multimodal Hemostatic Intervention in a Polytrauma Animal Model.

BACKGROUND: Life-threatening bleeding requires prompt reversal of the anticoagulant effects of factor Xa inhibitors. This study investigated the effectiveness of four-factor prothrombin complex concentrate in treating trauma-related hemorrhage with rivaroxaban-anticoagulation in a pig polytrauma model. This study also tested the hypothesis that the combined use of a low dose of prothrombin complex concentrate plus tranexamic acid and fibrinogen concentrate could improve its subtherapeutic effects. METHODS: Trauma (blunt liver injury and bilateral femur fractures) was induced in 48 anesthetized male pigs after 30 min of rivaroxaban infusion (1 mg/kg). Animals in the first part of the study received prothrombin complex concentrate (12.5, 25, and 50 U/kg). In the second part, animals were treated with 12.5 U/kg prothrombin complex concentrate plus tranexamic acid or plus tranexamic acid and fibrinogen concentrate. The primary endpoint was total blood loss postinjury. The secondary endpoints (panel of coagulation parameters and thrombin generation) were monitored for 240 min posttrauma or until death. RESULTS: The first part of the study showed that blood loss was significantly lower in the 25 U/kg prothrombin complex concentrate (1,541 ± 269 ml) and 50 U/kg prothrombin complex concentrate (1,464 ± 108 ml) compared with control (3,313 ± 634 ml), and 12.5 U/kg prothrombin complex concentrate (2,671 ± 334 ml, all P < 0.0001). In the second part of the study, blood loss was significantly less in the 12.5 U/kg prothrombin complex concentrate plus tranexamic acid and fibrinogen concentrate (1,836 ± 556 ml, P < 0.001) compared with 12.5 U/kg prothrombin complex concentrate plus tranexamic acid (2,910 ± 856 ml), and there were no early deaths in the 25 U/kg prothrombin complex concentrate, 50 U/kg prothrombin complex concentrate, and 12.5 U/kg prothrombin complex concentrate plus tranexamic acid and fibrinogen concentrate groups. Histopathologic analyses postmortem showed no adverse events. CONCLUSIONS: Prothrombin complex concentrate effectively reduced blood loss, restored hemostasis, and balanced thrombin generation. A multimodal hemostatic approach using tranexamic acid plus fibrinogen concentrate enhanced the effect of low doses of prothrombin complex concentrate, potentially reducing the prothrombin complex concentrate doses required for effective bleeding control.

Contrasting Role of Concentration in Rivaroxaban Induced Toxicity and Oxidative Stress in Isolated Kidney Mitochondria.

Rivaroxaban as a small molecule is able to directly and reversibly inhibit the factor Xa. This study was designed to figure out the evaluation effect of rivaroxaban on mitochondria obtained from rat kidneys. We isolated mitochondria from rat kidneys using gradient centrifugation. Then, the toxicity parameters including succinate dehydrogenase (SDH) activity, reactive oxygen species (ROS) formation, mitochondrial swelling, mitochondrial membrane potential (MMP) collapse and cytochrome c release were measured in kidneys mitochondria following the exposure to rivaroxaban. The results showed that rivaroxaban (1.4 and 2.8 mM) raised the reactive oxygen species (ROS) generation, swelling in the mitochondria, collapse in the mitochondrial membrane potential (MMP) and cytochrome c release in the mitochondria isolated from kidneys. While, rivaroxaban at a higher concentration of 5.6 mM showed the opposite effect compared to other lower concentrations. The results indicate that rivaroxaban may have antioxidant effects at high concentrations. The results suggest that rivaroxaban (5.6 mM) has protective effects against oxidative stress and mitochondrial toxicity.

In vitro toxicity assessment of rivaroxaban degradation products and kinetic evaluation to decay process.

Degradation kinetics of oral anticoagulant rivaroxaban (RIV) was assessed in acid and alkaline media and while exposed to UVC radiation. Among all stress conditions tested, kinetic degradation process was better described by a zero-order model. A stability indicating method was validated for the analysis of the anticoagulant RIV in tablets by high-performance liquid chromatography. Robustness was evaluated with a two-level Plackett-Burman experimental design. The effect of acute exposition of the human hepatoblastoma HepG2 cell line to RIV stressed samples (100 and 500 µM) was assessed through in vitro toxicity tests. MTT reduction, neutral red uptake, mitochondrial membrane potential, and low molecular weight DNA diffusion assays were employed for cytotoxicity evaluation (5×104 cells/well). The genotoxic potential was assessed by comet assay (2×104 cells/well). Acute toxicity to HepG2 cells was assessed after 24 h incubation with sample solutions, for each test. A direct relationship between the increased amount of alkaline degradation products and higher cytotoxic potential was found. Results obtained by viability assay investigations support the concerns on risks associated with acute toxicity and genotoxicity of pharmaceutical samples containing degradation products as impurities.

Thrombolysis with rt-PA under Rivaroxaban Anticoagulation in a Hypertensive Rat Model of Intraluminal Middle Cerebral Artery Occlusion.

BACKGROUND: The aim of this study was to assess the risk and the threshold of hemorrhagic transformation (HT) after treatment with recombinant tissue plasminogen activator (rtPA) under the novel oral anticoagulant, rivaroxaban. METHODS: Fifty-three spontaneous hypertensive rats were used in this study. We performed transient middle cerebral artery occlusion for 270 minutes. Placebo, 10 mg/kg or 20 mg/kg rivaroxaban were administered via a stomach tube 180 minutes after induction of ischemia, and rtPA (10 mg/kg) was administered just before reperfusion. Ninety minutes after rivaroxaban administration we measured the rivaroxaban plasma concentration and prothrombin time (PT). HT volume was assessed by hemoglobin spectrophotometry. Additionally, infarct volume, IgG leakage volume, and neurological outcome were assessed. RESULTS: Rivaroxaban plasma concentration and PT increased in a dose dependent manner but were lower than human peak levels after a once-daily dose of 20 mg rivaroxaban. HT volume increased after treatment with 20 mg/kg rivaroxaban compared with placebo treated controls or those treated with 10 mg/kg rivaroxaban (26.5 ± 5.4, 26.8 ± 8.7, and 41.4 ± 12.6 µL in placebo, 10 mg/kg, and 20 mg/kg treated groups, respectively; P < .05). CONCLUSIONS: Our results suggest that even at therapeutic plasma concentrations, rivaroxaban may increase the risk of HT after thrombolysis in some conditions, such as hypertension and/or a prolonged ischemic period.

Warfarin, but not rivaroxaban, promotes the calcification of the aortic valve in ApoE-/- mice.

INTRODUCTION: Vitamin K antagonists, such as warfarin, are known to promote arterial calcification through blockade of gamma-carboxylation of Matrix-Gla-Protein. It is currently unknown whether other oral anticoagulants such as direct inhibitors of Factor Xa can have protective effects on the progression of aortic valve calcification. AIMS: To compare the effect of warfarin and rivaroxaban on the progression of aortic valve calcification in atherosclerotic mice. RESULTS: 42 ApoE-/- mice fed with Western-type Diet (WTD) were randomized to treatment with warfarin (n = 14), rivaroxaban (n = 14) or control (n = 14) for 8 weeks. Histological analyses were performed to quantify the calcification of aortic valve leaflets and the development of atherosclerosis. The analyses showed a significant increase in valve calcification in mice treated with warfarin as compared to WTD alone (P = .025) or rivaroxaban (P = .005), whereas no significant differences were found between rivaroxaban and WTD (P = .35). Quantification of atherosclerosis and intimal calcification was performed on the innominate artery of the mice and no differences were found between the 3 treatments as far as atherogenesis and calcium deposition is concerned. In vitro experiments performed using bovine interstitial valve cells (VIC) showed that treatment with rivaroxaban did not prevent the osteogenic conversion of the cells but reduce the over-expression of COX-2 induced by inflammatory mediators. CONCLUSION: We showed that warfarin, but not rivaroxaban, could induce calcific valve degeneration in a mouse model of atherosclerosis. Both the treatments did not significantly affect the progression of atherosclerosis. Overall, these data suggest a safer profile of rivaroxaban on the risk of cardiovascular disease progression.

Evaluation of activated charcoal and lipid emulsion treatment in model of acute rivaroxaban toxicity.

AIM: Reducing or reversing the toxicity effects of new oral anticoagulants is an important question.The purpose of the present study is to evaluate the effect of lipid emulsion (LE) and Activated Charcoal (AC) therapy on the intoxication of rivaroxaban, on mice. METHODS: Adult male Balb/c mice weighing approximately 30g were used in the study. Seven groups were assigned, with six mice in each group. Groups were defined; given only rivaroxaban, given only LE, given only AC, after the administration of rivaroxaban LE applied group in the 1st hour, after the administration of rivaroxaban LE applied group in the 3rd hour, after the administration of rivaroxaban AC applied group in the1st hour, after the administration of rivaroxaban AC applied group in the 1st hour and LE applied group in the 3rd hour. PT and Anti-Factor Xa activity were measured in all blood samples from subjects. RESULTS: A statistically significant difference was found when all groups were compared in terms of mean PT values and Anti-FactorXa values. However, no statistically significant difference was found in the mean PT and Anti-FactorXa values when only rivaroxaban administrated group and after the administration of rivaroxaban LE and/or AC applied groups were compared one to one. No deaths occurred in groups during the observation. CONCLUSION: Although the administration of either AC or LE alone or in combination resulted in a decrease in the mean values of PT and anti-Factor Xa, in case of rivaroxaban toxicity, but one-to-one comparison of the groups was not statistically significant.

Inducing heat shock protein 70 expression provides a robust antithrombotic effect with minimal bleeding risk.

Antithrombotic medications target coagulation factors. Their use is associated with an increased bleeding risk. Safer drugs are needed. The heat shock protein 70 (Hsp70) exhibits antithrombotic properties that do not influence bleeding. By using murine models, we aimed to test the hypothesis that overexpressing Hsp70 with CM-695, a first in class dual inhibitor of HDAC6 and phosphodiesterase 9, protects against thrombosis while leaves bleeding tendency unaltered. CM-695 was used to induce Hsp70 overexpression. Hsp70 overexpressing mice were submitted to three thrombosis-triggering procedures. The ferric chloride carotid artery model was used to compare the antithrombotic role of CM-695 and rivaroxaban, a direct oral anticoagulant. The mouse tail transection model was used to compare the bleeding tendency upon CM-695 or rivaroxaban administration. Intraperitoneal (i. p.) 20 mg/kg CM-695 increased Hsp70 expression markedly in the murine aortic tissue. This treatment delayed thrombosis in the collagen/epinephrine [p=0.04 (Log-Rank test), n=10], Rose Bengal/laser [median vessel occlusion time (OT): 58.6 vs 39.0 minutes (min) in the control group (CG), p=0.008, n≥10] and ferric chloride (OT: 14.7 vs 9.2 min in the CG, p=0.032, n≥10) models. I.p. 80 mg/kg CM-695 (n≥9) and intravenous 3 mg/kg rivaroxaban (n≥8) significantly delayed thrombosis. CM-695 did not induce bleeding [median bleeding time (BT): 8.5 vs 7.5 min in the CG, n≥10]. However, BT was dramatically increased by rivaroxaban (30.0 vs 13.7 min in the CG, p=0.001, n=10). In conclusion, CM-695 is a new antithrombotic small molecule devoid of bleeding risk that may be envisioned as a useful clinical tool.

Rivaroxaban-induced chest wall spontaneous expanding hematoma.

Rivaroxaban is an oral direct Factor Xa inhibitor approved in the European Union and the United Sates for the single-drug treatment of several thromboembolic diseases in adults. Ιt has been evaluated in large phase III clinical trials and has been found to have similar efficacy and safety with standard therapy. Herein, is described a very rare case of a rivaroxaban-induced spontaneous expanding chest wall hematoma, that required surgical intervention, in a breast cancer patient. Use of the Naranjo adverse drug reaction probability scale indicated a probable relationship (score of 7) between the patient's development of hematoma and treatment with rivaroxaban. Physicians should be cautious when prescribing rivaroxaban in groups of patients associated with increased bleeding risk such as patients with impaired renal or hepatic function, hypertension, coronary heart disease, heart failure, patients with certain types of cancers and patients receiving concomitant medications which may alter the pharmacokinetic or pharmacodymamic parameters of rivaroxaban. Anticoagulant treatment should be tailored to each individual patient weighing the bleeding risk against the risk of recurrent thrombosis.

Is anti-factor Xa chromogenic assay for Rivaroxaban appropriate in clinical practice? Advantages and comparative drawbacks.

INTRODUCTION: No routine monitoring is required with factor Xa inhibitor rivaroxaban. Yet, its titration must be adapted, and its misuse may lead to increased risk of bleeding; therefore, therapeutic rivaroxaban monitoring might help in specific situations. MATERIAL AND METHODS: As asked by clinicians of our medical center, we measured rivaroxaban plasma concentrations in real conditions of use and checked their corresponding prescriptions. Measurement of 112 samples from 94 consecutive patients was performed with a Biophen LRT® anti-Xa chromogenic assay and compared blindly to the HPLC-MSMS "gold standard" method. Rivaroxaban was effectively given to 80 out of 94 patients but a mere 57% through an adequate prescription (within the scope of indications/titration). All chromogenic measurements were over the pre-specified 30ng/ml LOQ, whereas only 98 /114 samples had quantifiable rivaroxaban with HPLC-MSMS (LOQ 1ng/ml). Correlation between the two methods and linear regression were highly significant (p<0.0001). However, chromogenic values (mean 141.6ng/ml[96.6]) overestimated HPLC-MSMS values (119.7ng/ml[79.5]) by 22ng/ml according to Bland-Altman analysis (p<0.001). After re-assessing the chromogenic LOQ at 52ng/ml, 83 quantifiable samples had a mean concentration of 176.9ng/ml as compared to 158.5ng/ml with HPLC-MSMS, with no false positive anymore. CONCLUSIONS: In our medical center, rivaroxaban concentrations could be assessed by a rapid chromogenic method. Its pre-specified LOQ proved too high after being checked "on site" against HPLC-MSMS. Prescriptions for rivaroxaban were not optimal. An overestimated LOQ may impair observance monitoring or predispose patients to either risky thrombolysis or otherwise adjournable surgery in clinical practice.

Steps to diagnosis of a case of surreptitious intake of one of the newer direct oral anticoagulants: a case report and literature review.

Little is known about the effects of newer oral anticoagulants on various coagulation factors. When presented with a case of intentional or suspected overdose with an abnormal coagulation profile, it is imperative to have a working diagnostic algorithm to narrow the cause to a specific drug or drug class. This may become more crucial and time sensitive when dealing with a case of acute hemorrhage. Here we discuss the first reported case of what appears to be a surreptitious intake of newer oral anticoagulants and the steps leading to the diagnosis.