Warfarin-A natural anticoagulant: A review of research trends for precision medication.

BACKGROUND: Warfarin is a widely prescribed anticoagulant in the clinic. It has a more considerable individual variability, and many factors affect its variability. Mathematical models can quantify the quantitative impact of these factors on individual variability. PURPOSE: The aim is to comprehensively analyze the advanced warfarin dosing algorithm based on pharmacometrics and machine learning models of personalized warfarin dosage. METHODS: A bibliometric analysis of the literature retrieved from PubMed and Scopus was performed using VOSviewer. The relevant literature that reported the precise dosage of warfarin calculation was retrieved from the database. The multiple linear regression (MLR) algorithm was excluded because a recent systematic review that mainly reviewed this algorithm has been reported. The following terms of quantitative systems pharmacology, mechanistic model, physiologically based pharmacokinetic model, artificial intelligence, machine learning, pharmacokinetic, pharmacodynamic, pharmacokinetics, pharmacodynamics, and warfarin were added as MeSH Terms or appearing in Title/Abstract into query box of PubMed, then humans and English as filter were added to retrieve the literature. RESULTS: Bibliometric analysis revealed important co-occuring MeShH and index keywords. Further, the United States, China, and the United Kingdom were among the top countries contributing in this domain. Some studies have established personalized warfarin dosage models using pharmacometrics and machine learning-based algorithms. There were 54 related studies, including 14 pharmacometric models, 31 artificial intelligence models, and 9 model evaluations. Each model has its advantages and disadvantages. The pharmacometric model contains biological or pharmacological mechanisms in structure. The process of pharmacometric model development is very time- and labor-intensive. Machine learning is a purely data-driven approach; its parameters are more mathematical and have less biological interpretation. However, it is faster, more efficient, and less time-consuming. Most published models of machine learning algorithms were established based on cross-sectional data sourced from the database. CONCLUSION: Future research on personalized warfarin medication should focus on combining the advantages of machine learning and pharmacometrics algorithms to establish a more robust warfarin dosage algorithm. Randomized controlled trials should be performed to evaluate the established algorithm of warfarin dosage. Moreover, a more user-friendly and accessible warfarin precision medicine platform should be developed.

The combination of EGCG with warfarin reduces deep vein thrombosis in rabbits through modulating HIF-1α and VEGF via the PI3K/AKT and ERK1/2 signaling pathways.

Deep venous thrombosis (DVT) poses a major challenge to public health worldwide. Endothelial cell injury evokes inflammatory and oxidative responses that contribute to thrombus formation. Tea polyphenol (TP) in the form of epigallocatechin-3-gallate (EGCG) has anti-inflammatory and oxidative effect that may ameliorate DVT. However, the precise mechanism remains incompletely understood. The current study was designed to investigate the anti-DVT mechanism of EGCG in combination with warfarin (an oral anticoagulant). Rabbits were randomly divided into five groups. A DVT model of rats was established through ligation of the inferior vena cava (IVC) and left common iliac vein, and the animals were orally administered with EGCG, warfarin, or vehicle for seven days. In vitro studies included pretreatment of human umbilical vein endothelial cells (HUVECs) with different concentrations of EGCG for 2 h before exposure to hydrogen peroxide. Thrombus weight and length were examined. Histopathological changes were observed by hematoxylin-eosin staining. Blood samples were collected for detecting coagulation function, including thrombin and prothrombin times, activated partial thromboplastin time, and fibrinogen levels. Protein expression in thrombosed IVCs and HUVECs was evaluated by Western blot, immunohistochemical analysis, and/or immunofluorescence staining. RT-qPCR was used to determine the levels of AGTR-1 and VEGF mRNA in IVCs and HUVECs. The viability of HUVECs was examined by CCK-8 assay. Flow cytometry was performed to detect cell apoptosis and ROS generation was assessed by 2',7'-dichlorofluorescein diacetate reagent. In vitro and invivo studies showed that EGCG combined with warfarin significantly reduced thrombus weight and length, and apoptosis in HUVECs. Our findings indicated that the combination of EGCG and warfarin protects HUVECs from oxidative stress and prevents apoptosis. However, HIF-1α silencing weakened these effects, which indicated that HIF-1α may participate in DVT. Furthermore, HIF-1α silencing significantly up-regulated cell apoptosis and ROS generation, and enhanced VEGF expression and the activation of the PI3K/AKT and ERK1/2 signaling pathways. In conclusion, our results indicate that EGCG combined with warfarin modifies HIF-1α and VEGF to prevent DVT in rabbits through anti-inflammation via the PI3K/AKT and ERK1/2 signaling pathways.

Potential food-drug interaction risk of thymoquinone with warfarin.

Thymoquinone, predominant bioactive compound in Nigella sativa L. (N.sativa) oil, may inhibit the activity of cytochrome P450 2C9 (CYP2C9). However, it is not clear whether thymoquinone can affect the pharmacokinetic behavior of warfarin. Thus, we further to investigate the effect of thymoquinone on warfarin 7-hydroxylation activity and to quantitatively evaluate their food-drug interactions (FDIs) potential. Our data demonstrated that thymoquinone could inhibit warfarin 7-hydroxylase activity with IC50 value of 11.35 ± 0.25 µM. The kinetic analysis indicated that thymoquinone exhibited competitive inhibition on warfarin 7-hydroxylation with Ki value of 3.50 ± 0.44 µM. FDIs risk prediction suggested that coadministration of thymoquinone (>18 mg/day) or dietary supplements containing thymoquinone (N.sativa > 1 g/day or N. sativa oil >1 g/day) might influence pharmacokinetic behavior of warfarin. In conclusion, coadministration of thymoquinone or dietary supplements containing thymoquinone in warfarin-treated patients would likely trigger off unexpected potential drug interactions.

Effects and Mechanism of Action of Panax notoginseng Saponins on the Pharmacokinetics of Warfarin.

BACKGROUD: The interactions between Chinese herbs and drugs pose a great challenge to the combined clinical application of Chinese herbs and drugs. Chinese medicinal products contain complex pharmacologically active components that may influence the in vivo processes of drugs in a variety of ways. In China, drugs based on Panax ginseng total saponins (PNS) are often combined with warfarin for the treatment of cardiovascular diseases. OBJECTIVES: To assess the effects of Panax notoginseng saponins (PNS) on the pharmacokinetics of warfarin and its mechanism. METHOD: Blood was collected for the determination of the prothrombin time (PT) and international normalized ratio (INR) from rats treated with warfarin alone or with warfarin + PNS. The plasma concentration of warfarin was determined by high-performance liquid chromatography. Western blot was used to detect the expression of cytochrome P450 (CYP) enzymes. RESULTS: When warfarin and PNS were co-administered, the PT and INR increased compared to when warfarin was given alone. 72 hours after administration, compared to the warfarin alone group, the warfarin + low-dose PNS, warfarin + medium-dose PNS, and warfarin + high-dose PNS groups showed 110%, 122%, and 126% increases in PT, respectively (all P < 0.05), as well as 111%, 124%, and 128% increases in INR (all P < 0.05). Compared with the warfarin alone group, the clearance rate (CL/F) of warfarin in the warfarin + low-dose PNS, warfarin + medium-dose PNS, and warfarin + high-dose PNS groups was 10% (P > 0.05), 23% (P < 0.05), and 33% (P < 0.05) lower, respectively, while the systemic exposure (area under the concentration-time curve, AUC0-t) increased by 106% (P > 0.05), 119% (P < 0.05), and 134% (P < 0.05), respectively, and the blood concentration of warfarin incresed by 112%, 113%, and 114%, respectively (all P > 0.05). After combined treatment of HepG2 cells with warfarin + PNS, CYP1A2 expression was upregulated (P < 0.05) and CYP3A4 was downregulated (P < 0.05) but there was no effect on CYP2C9. In animal experiments, PNS had different effect on the expression of CYP1A2 in different doses. While a low dose of PNS resulted in downregulated CYP1A2 expression (P < 0.05), a medium dose resulted in upregulation (P < 0.05), and CYP1A2 expression was not significantly affected by a high dose of PNS (P > 0.05). Meanwhile, PNS at all doses downregulated the expression of CYP3A4 (P < 0.05) but had no effect on the expression of CYP2C9 (P > 0.05). CONCLUSION: PNS can increase the blood concentration of warfarin, as well as the exposure time, and it can enhance the anticoagulant effect of warfarin by inhibiting the expression of the liver enzyme CYP3A4.

Should patients with non-muscle-invasive bladder cancer discontinue fibrin clot inhibitors during bacille Calmette-Guérin?

OBJECTIVE: To determine the impact of fibrin clot inhibitor (FCI) use on oncological outcomes in a large contemporary cohort of patients with non-muscle-invasive bladder cancer (NMIBC) treated with adequate bacille Calmette-Guérin (BCG). PATIENTS AND METHODS: We performed an Institutional Review Board-approved review of patients with NMIBC treated with adequate intravesical BCG, at our institution between 2000 and 2018. FCI use at the time of BCG therapy was recorded for each patient. Patients were stratified according to use of FCI medication. Recurrence- and progression-free survival were analysed using Kaplan-Meier methods and Cox proportional hazard models. RESULTS: Overall, 226 of 526 patients (43.0%) used a FCI: aspirin (205), clopidogrel (38), warfarin (18) and novel oral anticoagulant (NOAC; seven). The use of FCIs did not adversely affect either recurrence- or progression-free survival (P = 0.385 and P = 0.131, respectively). These results did not change when the impact of aspirin, clopidogrel or warfarin/NOAC use on recurrence and progression was evaluated separately. On multivariate analysis, FCI use was neither associated with tumour recurrence nor progression. CONCLUSION: The use of FCIs was not associated with adverse oncological outcomes in a large contemporary cohort of patients receiving adequate intravesical BCG for NMIBC. Based on these results, FCIs may be safely continued during BCG immunotherapy.

The Comparison of Therapeutic Efficacy Between Dabigatran Versus Warfarin in Patients With Nonvalvular Atrial Fibrillation.

BACKGROUND: Novel oral anticoagulants and warfarin are widely used for stroke prevention in patients with atrial fibrillation. The anticoagulation status of patients receiving warfarin or rivaroxaban has been studied. In this study, we aimed to evaluate the effect of dabigatran and warfarin on preventing thrombin generation (TG). METHODS: This retrospective study enrolled 237 nonvalvular atrial fibrillation (NVAF) subjects treated with 110 mg dabigatran etexilate twice daily and 224 NVAF patients received adjusted-dose warfarin (international normalized ratio [INR] of 2 to 3)). Coagulation assays, prothrombin fragment 1 + 2 (F1+2), calibrated automated thrombogram, and thrombin-antithrombin complex (TAT) were detected at the steady state. RESULTS: Activated partial thromboplastin time (APTT), antithrombin III activity, fibrinogen, and lag time showed no difference between the two groups. Compared to the dabigatran group, prothrombin time and INR values were higher in the warfarin group (all P < .001). Thrombin time, endogenous thrombin potential, peak TG (Cmax), F1+2, and TAT were lower in the warfarin group. The inhibition of TG was still stronger in the warfarin group when the patients were divided into subgroups. CONCLUSION: Conventional coagulation assays are suboptimal for assessing the coagulation status of dabigatran. TG could be used as supplementary assays to evaluate the anticoagulation effect of oral anticoagulants. Our results suggest that warfarin may inhibit TG more aggressively than dabigatran in patients regardless of age and kidney function.

Molecular Mechanism of Vitamin K2 Protection against Amyloid-ß-Induced Cytotoxicity.

The pathological role of vitamin K2 in Alzheimer's disease (AD) involves a definite link between impaired cognitive functions and decreased serum vitamin K levels. Vitamin K2 supplementation may have a protective effect on AD. However, the mechanism underlying vitamin K2 protection has not been elucidated. With the amyloid-ß (Aß) cascade hypothesis, we constructed a clone containing the C-terminal fragment of amyloid precursor protein (ß-CTF/APP), transfected in astroglioma C6 cells and used this cell model (ß-CTF/C6) to study the protective effect of vitamin K2 against Aß cytotoxicity. Both cellular and biochemical assays, including cell viability and reactive oxygen species (ROS), assays assay, and Western blot and caspase activity analyses, were used to characterize and unveil the protective role and mechanism of vitamin K2 protecting against Aß-induced cytotoxicity. Vitamin K2 treatment dose-dependently decreased the death of neural cells. The protective effect of vitamin K2 could be abolished by adding warfarin, a vitamin K2 antagonist. The addition of vitamin K2 reduced the ROS formation and inhibited the caspase-3 mediated apoptosis induced by Aß peptides, indicating that the mechanism underlying the vitamin K2 protection is likely against Aß-mediated apoptosis. Inhibitor assay and Western blot analyses revealed that the possible mechanism of vitamin K2 protection against Aß-mediated apoptosis might be via regulating phosphatidylinositol 3-kinase (PI3K) associated-signaling pathway and inhibiting caspase-3-mediated apoptosis. Our study demonstrates that vitamin K2 can protect neural cells against Aß toxicity.

Effects of Herba Erigerontis injection on pharmacodynamics and pharmacokinetics of warfarin in rats in vivo.

Herba Erigerontis injection (HEI) is an aqueous solution derived from whole plants of Erigeron breviscapus, which may be co-administered with warfarin to treat cardiovascular and cerebrovascular disorders. This research was conducted to make sure whether HEI would affect anticoagulation of warfarin to guarantee reasonable medication. The pharmacodynamic study was designed to measure prothrombin time (PT) and activated partial thromboplastin time (APTT) values, and international normalized ratio (INR) values were calculated. For pharmacokinetic study, ultra performance liquid chromatography-tandem mass spectrometer (UPLC-MS/MS) technology was applied to measure plasma concentrations of warfarin enantiomers. The influence of HEI on plasma protein binding rate of warfarin was assessed by ultrafiltration. Pharmacodynamic study demonstrated that both HEI alone and co-administered with warfarin could increase PT and INR values significantly (P < .01), whereas the APTT values were unaffected (P > .05). Pharmacokinetic study manifested that Cmax , AUC and t1/2 prolonged significantly (P < .01) for R/S-warfarin in presence of HEI. Low (3.6 mL/kg), medium (7.2 mL/kg) and high (10.8 mL/kg) doses of HEI could decrease plasma protein binding rate of warfarin significantly (P < .01). The results mean that HEI can potentiate the anticoagulant response of warfarin through both pharmacodynamics and pharmacokinetics.

Rivaroxaban Versus Warfarin for Management of Obese African Americans With Non-Valvular Atrial Fibrillation or Venous Thromboembolism: A Retrospective Cohort Analysis.

African Americans (AAs) and obese individuals have increased thrombotic risk. This study evaluated the effectiveness and safety of rivaroxaban versus warfarin in obese, AAs with nonvalvular atrial fibrillation (NVAF) or venous thromboembolism (VTE). Optum® De-Identified Electronic Health Record (EHR) data was used to perform separate propensity-score matched analyses of adult, oral anticoagulant (OAC)-naïve AAs with NVAF or acute VTE, respectively; who had a body mass index≥30kg/m2 and ≥12-months EHR activity with ≥1-encounter before OAC initiation. Cox regression was performed and reported as hazard ratios (HRs) with 95% confidence intervals (CIs). For the NVAF analysis, 1,969 rivaroxaban- and 1,969 warfarin-users were matched. Rivaroxaban was not associated with a difference in stroke/systemic embolism versus warfarin (HR = 0.88, 95%CI = 0.60-1.28), but less major bleeding (HR = 0.68, 95%CI = 0.50-0.94) was observed. Among 683 rivaroxaban-users with VTE, 1:1 matched to warfarin-users, rivaroxaban did not alter recurrent VTE (HR = 1.36, 95%CI = 0.79-2.34) or major bleeding (HR = 0.80, 95%CI = 0.37-1.71) risk versus warfarin at 6-months (similar findings observed at 3- and 12-months). Rivaroxaban appeared to be associated with similar thrombotic, and similar or lower major bleeding risk versus warfarin in these obese, AA cohorts.

The Potential Role of Undercarboxylated Osteocalcin Upregulation in Microvascular Insufficiency in a Rat Model of Diabetic Cardiomyopathy.

BACKGROUND: Diabetic cardiomyopathy (DCM) is accompanied by microvascular complications that lead to myocardial dysfunction and heart failure. Most conventional therapies cannot ameliorate the microvascular insufficiency in DCM. In this study, we tested the hypothesis that undercarboxylated osteocalcin (ucOC) may be a new adjuvant therapy against the progression of DCM and its underlying microvascular pathology. MATERIALS AND METHODS: Diabetes was induced in Wistar rats with a high-fat diet combined with streptozotocin injections, and ucOC was upregulated after warfarin administration in the treated group. After 8 weeks, cardiac functions were assessed using a Langendorff apparatus. Cardiac tissue samples were also extracted to assess the ucOC receptor and vascular endothelial growth factor (VEGF) for histopathological studies. RESULTS: Both the systolic and the diastolic dysfunction observed in the DCM group were significantly improved after the increase in ucOC blood levels. Significant improvement in VEGF and CD31 expression after warfarin injection was associated with increased capillary density, neovascularization, and decreased myocardial fibrosis together with the reestablishment of myocardial structural and ultrastructural patterns. CONCLUSION: Undercarboxylated osteocalcin may have a promising effect in improving microvascular insufficiency and myocardial dysfunction in DCM.

CYP2C9-mediated warfarin and milk thistle interaction.

WHAT IS KNOWN AND OBJECTIVE: In vitro studies suggest a CYP2C9-mediated interaction between milk thistle and warfarin, but there has been no in vivo case report on this interaction. CASE DESCRIPTION: A White Hispanic man in his 30s was well controlled on warfarin therapy for mitral valve replacement. His INR increased from 2.64 to 4.12, and he denied changes to his medications and diet but noted starting a 'liver cleanse' supplement which contained milk thistle (200 mg). After stopping the supplement his INR normalized, and he remains on the same warfarin dose. WHAT IS NEW AND CONCLUSION: This is the first in vivo report of an interaction between milk thistle and warfarin.

A study to evaluate herb-drug interaction underlying mechanisms: An investigation of ginsenosides attenuating the effect of warfarin on cardiovascular diseases.

Warfarin and ginseng have been widely used in the treatment of cardiovascular diseases. However, the clinical safety and effectiveness of herb-drug combination treatment are still controversial. Therefore, it is very essential to probe the interaction between warfarin and ginseng. In this study, in vitro and in vivo study was carried out to demonstrate that whether there is an interaction between warfarin and ginsenosides (GS), which is the main component of ginseng. In vitro study showed that the adhesion ability between endothelial cells and matrigel/platelets was enhanced due to the up-regulating expression of intercellular adhesion molecule (ICAM-1) and vascular cell adhesion molecule (VCAM-1) proteins by treatment of warfarin+GS combination compared to warfarin/GS treatment alone. Moreover, GS could weaken the anticoagulation effect of warfarin in hyperlipemia rats owning to the increased expression levels of coagulation factors and hepatic cytochrome P450 enzymes in plasma after long-term co-administration of warfarin with GS. The results of both in vitro and in vivo study demonstrated that there is a serious interaction between warfarin and ginseng, which may deteriorate atherosclerosis and thrombosis after combined use of warfarin and GS.

Resolution of acute lower extremity deep vein thrombosis with rivaroxaban compared to warfarin.

Thrombosis resolution is an important component of treatment for deep vein thrombosis (DVT) and multiple anticoagulants are now available. It is unknown whether rivaroxaban contributes to a higher degree of thrombus resolution compared to conventional anticoagulation with warfarin. Our objective was to compare thrombus resolution for rivaroxaban versus warfarin treated patients with acute lower extremity DVT. Consecutive patients treated for proximal or distal lower extremity DVT with rivaroxaban were identified from the Mayo Thrombophilia Clinic Anticoagulants Registry (November 2015-June 2016) and compared to patients treated with warfarin. Ultrasonography/Doppler images were analyzed by two independent radiologists blinded to anticoagulant and using a standardized assessment algorithm. A total of 111 patients with DVT were studied. Sixty-three rivaroxaban treated patients were compared to 48 warfarin treated patients over a median follow up of 92 and 97 days, respectively. Percentage of patients with total or partial resolution of thrombosis was similar in rivaroxaban and warfarin treated groups (95.2% vs. 91.7%, p = 0.46, respectively); also the proportion of patients with total thrombus resolution was not significantly different (38.1% vs. 29.2%, p = 0.42, respectively). There was no significant difference in the proportion of patients with no thrombus resolution between rivaroxaban and warfarin treated groups either (4.8% vs. 2.1%, p = 0.63). Thrombus propagation with warfarin therapy was observed in 6.3% of patients treated with warfarin and in none of the patients from the rivaroxaban group (p = 0.08). Resolution of acute lower extremity DVT in patients treated with rivaroxaban is similar to those treated with warfarin.

[Comparison of efficacy of rivaroxaban and warfarin after open operations on the infrainguinal segment]. / Sravnenie éffektivnosti rivaroksabana i varfarina posle otkrytykh operatsii na infraingvinal'nom segmente.

The authors analysed oral anticoagulant agents prescribed in the postoperative period to patients after endured reconstructive operative intervention on arteries of the femorotibial segment. The study included a total of 104 patients subjected to femoropopliteal or femorotibial bypass grafting using an autologous vein or a prosthesis. Depending on the prescribed anticoagulation agent, the patients were subdivided into two groups. Group One patients (n=43) in the postoperative period received rivaroxaban, and Group Two patients (n=61) took warfarin. Efficacy of therapy was evaluated by the frequency of haemorrhage and thromboses in the early and remote postoperative periods. The findings of the immediate postoperative period demonstrated comparable rates of haemorrhagic complications, early thromboses and redo interventions in both Groups (p=0.7). The duration of long-term postoperative period varied from 3 months to 5 years. No statistically significant differences in patency of the performed reconstructions were revealed between the groups. The 3-year primary assisted patency rate in the rivaroxaban group and warfarin group amounted to 89 and 80%, respectively. The incidence of haemorrhagic complications in the postoperative period was insignificant in the studied groups. Hence, rivaroxaban may be prescribed in the early and remote postoperative period to patients who underwent open reconstructive operative intervention on arteries of the infrainguinal zone.

Rivaroxaban's Impact on Renal Decline in Patients With Nonvalvular Atrial Fibrillation: A US MarketScan Claims Database Analysis.

Warfarin has been associated with renovascular calcification and worsening renal function, whereas rivaroxaban may provide a degree of renopreservation by decreasing vascular inflammation. We sought to compare rivaroxaban and warfarin's impact on renal decline in patients with nonvalvular atrial fibrillation (NVAF) treated in routine practice. Using US MarketScan claims data from January 2012 to December 2017, we identified patients with NVAF newly initiated on rivaroxaban or warfarin with ≥12 months of continuous insurance coverage prior to initiation. Patients with stage 5 chronic kidney disease (CKD) or receiving hemodialysis at baseline were excluded. Outcomes included rates (events/100 person-years) of hospital or emergency department admission for acute kidney injury (AKI) or progression to stage 5 CKD or need for hemodialysis. Differences in baseline covariates between cohorts were adjusted using inverse probability-of-treatment weights based on propensity scores (absolute standardized differences <0.1 achieved for all covariates after adjustment). Patients were followed until an event, anticoagulant discontinuation/switch, insurance disenrollment, or end of data availability. Hazard ratios with 95% confidence intervals (CIs) were estimated using Cox regression. We assessed 36 318 rivaroxaban (19.8% received a dose <20 mg/d) and 36 281 warfarin users. Stages 3 and 4 CKD were present in 5% and 1% of patients at baseline, and proteinuria was present in 2%. Rivaroxaban was associated with a 19% (95% CI = 13%-25%) reduction in the hazard of AKI (rates = 4.91 vs 8.45) and an 18% (95% CI = 9%-26%) reduction in progression to stage 5 CKD or hemodialysis (rates = 2.67 vs 4.12). Rivaroxaban appears associated with lower hazards of undesirable renal end points versus warfarin in patients with NVAF.

Critical pharmacokinetic and pharmacodynamic drug-herb interactions in rats between warfarin and pomegranate peel or guava leaves extracts.

BACKGROUND: In-depth information of potential drug-herb interactions between warfarin and herbal compounds with suspected anticoagulant blood thinning effects is needed to raise caution of concomitant administration. The current study aimed to investigate the impact of co-administration of pomegranate peel and guava leaves extracts, including their quality markers namely; ellagic acid and quercetin, respectively, on warfarin's in vivo dynamic activity and pharmacokinetic actions, in addition to potential in vitro cytochrome P450 enzymes (CYP) inhibition. METHODS: Influence of mentioned extracts and their key constituents on warfarin pharmacodynamic and kinetic actions and CYP activity were evaluated. The pharmacodynamic interactions were studied in Sprague Dawley rats through prothrombin time (PT) and International Normalized Ratio (INR) measurements, while pharmacokinetic interactions were detected in vivo using a validated HPLC method. Furthermore, potential involvement in CYP inhibition was also investigated in vitro on isolated primary rat hepatocytes. RESULTS: Preparations of pomegranate peel guava leaf extract, ellagic acid and quercetin in combination with warfarin were found to exert further significant increase on PT and INR values (p < 0.01) than when used alone (p < 0.05). Pomegranate peel extract showed insignificant effects on warfarin pharmacokinetics (p > 0.05), however, its constituent, namely, ellagic acid significantly increased warfarin Cmax (p < 0.05). Guava leaves extract and quercetin resulted in significant increase in warfarin Cmax when compared to control (p < 0.01). Furthermore, guava leaves extract showed a significant effect on changing the AUC, CL and Vz. Significant reduction in CYP2C8, 2C9, and 3A4 was seen upon concomitant use of warfarin with ellagic acid, guava leaves and quercetin, unlike pomegranate that insignificantly affected CYP activities. CONCLUSION: All combinations enhanced the anticoagulant activity of warfarin as the results of in vivo and in vitro studies were consistent. The current investigation confirmed serious drug herb interactions between warfarin and pomegranate peel or guava leaf extracts. Such results might conclude a high risk of bleeding from the co-administration of the investigated herbal drugs with warfarin therapy. In addition, the results raise attention to the blood-thinning effects of pomegranate peel and guava leaves when used alone.

Real-world clinical evidence on rivaroxaban, dabigatran, and apixaban compared with vitamin K antagonists in patients with nonvalvular atrial fibrillation: a systematic literature review.

INTRODUCTION: Several comparative real-world effectiveness studies on direct oral anticoagulants (DOACs) have been conducted, but an overview of the available evidence remains to be developed, which could provide a better understanding of the value of DOACs relative to vitamin K antagonists (VKAs). AREAS COVERED: A systematic literature review was conducted on the available real-world evidence (RWE) of three DOACs (rivaroxaban, dabigatran, and apixaban) compared with VKAs (e.g. warfarin), in patients with nonvalvular atrial fibrillation (NVAF).This systematic literature review included RWE published up to December 2016. Studies with > 50 patients reporting on incident and prevalent NVAF cases were included. The following databases were searched: Medline, Embase, and the Cochrane Library. Outcomes of interest included thromboembolic events, all-cause mortality, bleeding events, and nonpersistence. Of the 562 RWE DOACs articles retrieved, 49 presented results for rivaroxaban versus VKAs, 79 for dabigatran versus VKAs, and 18 for apixaban versus VKAs. Substantial heterogeneity was found across patient population, outcome definition, and follow-up period. Major bleeding, ischemic stroke, and intracranial hemorrhage were the most frequent outcomes analyzed. EXPERT COMMENTARY: Overall, the RWE studies were aligned with the Phase 3 trials. However, conflicting results were reported for several outcomes of interest.

Evaluation of oral anticoagulants with vitamin K epoxide reductase in its native milieu.

Warfarin, acenocoumarol, phenprocoumon, and fluindione are commonly prescribed oral anticoagulants for the prevention and treatment of thromboembolic disorders. These anticoagulants function by impairing the biosynthesis of active vitamin K-dependent coagulation factors through the inhibition of vitamin K epoxide reductase (VKOR). Genetic variations in VKOR have been closely associated with the resistant phenotype of oral anticoagulation therapy. However, the relative efficacy of these anticoagulants, their mechanisms of action, and their resistance variations among naturally occurring VKOR mutations remain elusive. Here, we explored these questions using our recently established cell-based VKOR activity assay with the endogenous VKOR function ablated. Our results show that the efficacy of these anticoagulants on VKOR inactivation, from most to least, is: acenocoumarol > phenprocoumon > warfarin > fluindione. This is consistent with their effective clinical dosages for stable anticoagulation control. Cell-based functional studies of how each of the 27 naturally occurring VKOR mutations responds to these 4 oral anticoagulants indicate that phenprocoumon has the largest resistance variation (up to 199-fold), whereas the resistance of acenocoumarol varies the least (<14-fold). Cell-based kinetics studies show that fluindione appears to be a competitive inhibitor of VKOR, whereas warfarin is likely to be a mixed-type inhibitor of VKOR. The anticoagulation effect of these oral anticoagulants can be reversed by the administration of a high dose of vitamin K, apparently due to the existence of a different enzyme that can directly reduce vitamin K. These findings provide new insights into the selection of oral anticoagulants, their effective dosage management, and their mechanisms of anticoagulation.

Dabigatran, rivaroxaban and apixaban vs. high TTR warfarin in atrial fibrillation.

INTRODUCTION: New oral anticoagulants are non-inferior compared with warfarin regarding stroke prevention in atrial fibrillation, with similar or decreased risk of bleeding. However, it is unclear whether high TTR warfarin is as effective and safe as NOACs. Our objective was to investigate efficacy and safety of apixaban, dabigatran or rivaroxaban compared with warfarin in clinical practice. MATERIALS AND METHODS: Nationwide retrospective cohort study based on Swedish quality registries. Atrial fibrillation patients initiated on apixaban, dabigatran, rivaroxaban or warfarin between 2013-01-01 and 2015-12-31 were included. Main outcome measures were all-cause stroke and systemic embolism, all-cause stroke, ischemic stroke, hemorrhagic stroke; major bleeding, intracranial bleeding, gastrointestinal bleeding, other bleeding (fatal or requiring hospital care); all-cause mortality; myocardial infarction. RESULTS: The study included 64,382 patients corresponding to 81,176 treatment years. Of these, 37,174 patients were instituted on warfarin, 6574 on dabigatran, 8323 on rivaroxaban and 12,311 on apixaban. In warfarin treated patients, the time in therapeutic range was 71.4%. After propensity score matching, there was no significant difference in risk of stroke or systemic embolism between NOAC and warfarin treated patients. Hazard ratios for major bleeding events were 0.63(95%CI 0.52-0.75) for apixaban, 0.74(0.62-0.87) for dabigatran and 1.06(0.92-1.23) for rivaroxaban, compared with warfarin. CONCLUSIONS: This study showed no difference between apixaban, dabigatran, or rivaroxaban compared to high TTR warfarin treatment regarding stroke prevention. However, fewer bleeding events were seen for apixaban and dabigatran, but not for rivaroxaban. Further studies are needed on the comparability of individual NOACs with respect to bleeding risks.

Effectiveness and safety of outpatient rivaroxaban versus warfarin for treatment of venous thromboembolism in patients with a known primary hypercoagulable state.

INTRODUCTION: Screening for primary hypercoagulable states (PHSs) in venous thromboembolism (VTE) patients was not mandated in the EINSTEIN trials; and therefore, few patients with a known PHS were available for analysis. We sought to assess the effectiveness and safety of rivaroxaban versus warfarin for treatment of VTE in patients with a known PHS. METHODS: Using MarketScan claims data from 1/2012-9/2015, we identified adults with a primary diagnosis of VTE during a hospitalization/emergency department visit (the index event), with ≥180-days of continuous insurance coverage prior to the index event, a documented diagnosis for a PHS and newly-initiated as an outpatient on rivaroxaban or warfarin within 30-days of the index VTE. Rivaroxaban and warfarin users were 1:1 propensity-score matched. Balance between cohorts was evaluated by inspecting standardized differences for baseline covariates (<0.1 considered well-balanced). Patients were followed up to 12-months from the index event or until occurrence of an endpoint, switch/discontinuation of index oral anticoagulation or insurance disenrollment. Rates of recurrent VTE and major bleeding were compared using Cox regression and reported as hazard ratios (HRs) with 95% confidence intervals (CIs). RESULTS: We matched 403 rivaroxaban and 403 warfarin patients with VTE and a known PHS. All baseline covariates had a standardized difference < 0.1. Rivaroxaban use was associated with a non-significant reduction in recurrent VTE (HR = 0.70, 95%CI = 0.33-1.49) and major bleeding (HR = 0.55, 95%CI = 0.16-1.86) versus warfarin. CONCLUSIONS: In routine practice, the effectiveness and safety of rivaroxaban versus warfarin in VTE patients with a known PHS appears to be similar to that observed in the EINSTEIN trial program.