Enhanced Oral Bioavailability of Rivaroxaban-Loaded Microspheres by Optimizing the Polymer and Surfactant Based on Molecular Interaction Mechanisms.

This study aimed to develop microspheres using water-soluble carriers and surfactants to improve the solubility, dissolution, and oral bioavailability of rivaroxaban (RXB). RXB-loaded microspheres with optimal carrier (poly(vinylpyrrolidone) K30, PVP) and surfactant (sodium lauryl sulfate (SLS)) ratios were prepared. 1H NMR and Fourier transform infrared (FTIR) analyses showed that drug-excipient and excipient-excipient interactions affected RXB solubility, dissolution, and oral absorption. Therefore, molecular interactions between RXB, PVP, and SLS played an important role in improving RXB solubility, dissolution, and oral bioavailability. Formulations IV and VIII, containing optimized RXB/PVP/SLS ratios (1:0.25:2 and 1:1:2, w/w/w), had significantly improved solubility by approximately 160- and 86-fold, respectively, compared to RXB powder, with the final dissolution rates improved by approximately 4.5- and 3.4-fold, respectively, compared to those of RXB powder at 120 min. Moreover, the oral bioavailability of RXB was improved by 2.4- and 1.7-fold, respectively, compared to that of RXB powder. Formulation IV showed the highest improvement in oral bioavailability compared to RXB powder (AUC, 2400.8 ± 237.1 vs 1002.0 ± 82.3 h·ng/mL). Finally, the microspheres developed in this study successfully improved the solubility, dissolution rate, and bioavailability of RXB, suggesting that formulation optimization with the optimal drug-to-excipient ratio can lead to successful formulation development.

Evaluation of Xa inhibitors as potential inhibitors of the SARS-CoV-2 Mpro protease.

Based on previous large-scale in silico screening several factor Xa inhibitors were proposed to potentially inhibit SARS-CoV-2 Mpro. In addition to their known anticoagulants activity this potential inhibition could have an additional therapeutic effect on patients with COVID-19 disease. In this study we examined the binding of the Apixaban, Betrixaban and Rivaroxaban to the SARS-CoV-2 Mpro with the use of the MicroScale Thermophoresis technique. Our results indicate that the experimentally measured binding affinity is weak and the therapeutic effect due to the SARS-CoV-2 Mpro inhibition is rather negligible.

Review on Characteristics and Analytical Methods of Rivaroxaban.

Rivaroxaban (RIV) is an oral anticoagulant that is the first available orally active direct inhibitor of factor Xa. This study focuses on a critical review of the mechanisms of action, characteristics, operations, physicochemical properties of RIV, and analytical methodologies to quantify the concentration of the agent in bulk, pharmaceutical formulations, dissolution media, and biological samples. The major analytical methodology for the determination of RIV is reverse-phase HPLC coupled with UV detection and LC-MS/MS. This technique is particularly beneficial to detect and analyze RIV in plasma samples. The methodologies published in literature until recently were tabulated and the sample preparation techniques prior to analyzes of the biological matrix were discussed. Based on this critical literature screening, it was concluded that the researchers may easily apply or modify the published methodologies depending on their purpose on further studies since the chemical and physical properties of RIV allows this agent to be extracted and analyzed by employing different analytical strategies.

UVPD Spectroscopy of Differential Mobility-Selected Prototropic Isomers of Rivaroxaban.

Two ion populations of protonated Rivaroxaban, [C19H18ClN3O5S + H]+, are separated under pure N2 conditions using differential mobility spectrometry prior to characterization in a hybrid triple quadrupole linear ion trap mass spectrometer. These populations are attributed to bare protonated Rivaroxaban and to a proton-bound Rivaroxaban-ammonia complex, which dissociates prior to mass-selecting the parent ion. Ultraviolet photodissociation (UVPD) and collision-induced dissociation (CID) studies indicate that both protonated Rivaroxaban ion populations are comprised of the computed global minimum prototropic isomer. Two ion populations are also observed when the collision environment is modified with 1.5% (v/v) acetonitrile. In this case, the protonated Rivaroxaban ion populations are produced by the dissociation of the ammonium complex and by the dissociation of a proton-bound Rivaroxaban-acetonitrile complex prior to mass selection. Again, both populations exhibit a similar CID behavior; however, UVPD spectra indicate that the two ion populations are associated with different prototropic isomers. The experimentally acquired spectra are compared with computed spectra and are assigned to two prototropic isomers that exhibit proton sharing between distal oxygen centers.

Sensitive LC-MS/MS method for quantification of rivaroxaban in plasma: Application to pharmacokinetic studies.

Rivaroxaban is an anticoagulant (orally active direct Xa inhibitor) considered to reduce the risk of stroke and systemic embolism and treat deep vein thrombosis, pulmonary embolism, and other cardiovascular complications. Bioanalytical methods for rivaroxaban quantification in plasma are necessary for application in pharmacokinetic studies, as well as in drug therapeutic monitoring. In this work, we developed and validated a sensitive bioanalytical method using LC-MS/MS for rivaroxaban quantification in human plasma using an one-step liquid-liquid extraction. The linear concentration range was 1-600 ng/mL. The bioanalytical method was also applied to pharmacokinetic studies in healthy volunteers under fasting and fed conditions. The results demonstrated that the method is rapid, sensitive, and adequate for application in pharmacokinetic studies.

Novel rivaroxaban-loaded poly(lactic-co-glycolic acid)/poloxamer nanoparticles: preparation, physicochemical characterization, in vitro evaluation of time-dependent anticoagulant activity and toxicological profile.

Rivaroxaban (RXB), an oral direct factor Xa inhibitor, presents innovative therapeutic profile. However, RXB has shown adverse effects, mainly due to pharmacokinetic limitations, highlighting the importance of developing more effective formulations. Therefore, this work aims at the preparation, physicochemical characterization and in vitro evaluation of time-dependent anticoagulant activity and toxicology profile of RXB-loaded poly(lactic-co-glycolic acid) (PLGA)/poloxamer nanoparticles (RXBNps). RXBNp were produced by nanoprecipitation method and physicochemical characteristics were evaluated. In vitro analysis of time-dependent anticoagulant activity was performed by prothrombin time test and toxicological profile was assessed by hemolysis and MTT reduction assays. The developed RXBNp present spherical morphology with average diameter of 205.5 ± 16.95 nm (PdI 0.096 ± 0.04), negative zeta potential (-26.28 ± 0.77 mV), entrapment efficiency of 91.35 ± 2.40%, yield of 41.81 ± 1.68% and 3.72 ± 0.07% of drug loading. Drug release was characterized by an initial fast release followed by a sustained release with 28.34 ± 2.82% of RXB available in 72 h. RXBNp showed an expressive time-dependent anticoagulant activity in human and rat blood plasma and non-toxic profile. Based on the results presented, it is possible to consider that RXBNp may be able to assist in the development of promising new therapies for treatment of thrombotic disorders.

Binding of direct oral anticoagulants to the FA1 site of human serum albumin.

The anticoagulant therapy is widely used to prevent and treat thromboembolic events. Until the last decade, vitamin K antagonists were the only available oral anticoagulants; recently, direct oral anticoagulants (DOACs) have been developed. Since 55% to 95% of DOACs are bound to plasma proteins, the in silico docking and ligand-binding properties of drugs apixaban, betrixaban, dabigatran, edoxaban, and rivaroxaban and of the prodrug dabigatran etexilate to human serum albumin (HSA), the most abundant plasma protein, have been investigated. DOACs bind to the fatty acid (FA) site 1 (FA1) of ligand-free HSA, whereas they bind to the FA8 and FA9 sites of heme-Fe(III)- and myristic acid-bound HSA. DOACs binding to the FA1 site of ligand-free HSA has been validated by competitive inhibition of heme-Fe(III) recognition. Values of the dissociation equilibrium constant for DOACs binding to the FA1 site (ie, calc KDOAC ) derived from in silico docking simulations (ranging between 1.2 × 10-8 M and 1.4 × 10-6 M) agree with those determined experimentally from competitive inhibition of heme-Fe(III) binding (ie, exp KDOAC ; ranging between 2.5 × 10-7 M and 2.2 × 10-6 M). In addition, this study highlights the inequivalence of rivaroxaban binding to mammalian serum albumin. Given the HSA concentration in vivo (~7.5 × 10-4 M), values of KDOAC here determined indicate that the formation of the HSA:DOACs complexes in the absence and presence of FAs and heme-Fe(III) may occur in vivo. Therefore, HSA appears to be an important determinant for DOACs transport.

Assessment of Dose Proportionality of Rivaroxaban Nanocrystals.

Rivaroxaban (RXB) is a class II drug, according to the Biopharmaceutics Classification System. Since its bioavailability is low at high doses, dose proportionality is not achieved for pharmacokinetic parameters. However, when taken with food, its bioavailability increases at high doses. In this study, nanocrystal technology was used to increase the solubility and, hence, the bioavailability of RXB. Pluronic F127, pharmacoat 603, and PVP K-30 were used as stabilizers to prepare RXB nanosuspension, combining ball mill and high pressure homogenization methods. Particle sizes of RXB in nanosuspension (formulation A:348 nm; formulation B:403 nm) and nanocrystal formulations (formulation A:1167 nm; formulation B:606 nm) were significantly reduced (p < 0.05) compared to those of bulk RXB. In both formulations, 80% of the drug dissolved in 30 min. For dose proportionality evaluation, 3, 10, and 15 mg/kg of RXB nanosuspensions (formulation B) were administered to rabbits. The dose proportionality for AUC and Cmax of RXB nanocrystals was assessed by the power model, variance analysis of pharmacokinetic parameters, linear regression, and equivalence criterion methods. Dose proportionality for AUC was achieved at doses between 10-15 and 3-15 mg/kg. In conclusion, the preparation of a nanocrystal formulation of RXB improved its dissolution rate and pharmacokinetic profile.

Sustained release and enhanced oral bioavailability of rivaroxaban by PLGA nanoparticles with no food effect.

The purpose of the currents study was to enhance bioavailability of rivaroxaban (RXB) and reduce the food effect. RXB loaded PLGA nanoparticles (RXB-PLGA-NPs) were prepared by emulsion solvent evaporation method and optimized using central composite design (CDD). The optimized RXB-PLGA-NPs (F8) with composition, PLGA (125 mg), PVA (0.5%w/w) and RXB (20 mg) was found optimum with particle size (496 ± 8.5 nm), PDI (0.607), ZP (- 18.41 ± 3.14 mV), %EE (87.9 ± 8.6) and %DL (9.5 ± 1.6). The optimized NPs (F8) was further evaluated in vitro for DSC, FTIR, SEM and in vitro release studies. A comparative pharmacokinetic studies with commercial tablet (XARELTO®) were conducted on fasted and fed state rats. Compared to commercial tablet (XARELTO®), the RXB-PLGA-NPs (F8) exhibited a significant enhancement of bioavailability in both fasted and fed state. In addition, the bioavailability of RXB from NPs (F8) was found unaffected in the presence of food.

Chromogenic anti-FXa assay calibrated with low molecular weight heparin in patients treated with rivaroxaban and apixaban: possibilities and limitations.

INTRODUCTION: Clinical application of rivaroxaban and apixaban does not require therapeutic monitoring. Commercial anti-activated factor X (anti-FXa) inhibition methods for all anti-FXa drugs are based on the same principle, so there are attempts to evaluate potential clinical application of heparin-calibrated anti-FXa assay as an alternative method for direct FXa inhibitors. We aimed to evaluate relationship between anti-FXa methods calibrated with low molecular weight heparin (LMWH) and with drug specific calibrators, and to determine whether commercial LMWH anti-FXa assay can be used to exclude the presence of clinically relevant concentrations of rivaroxaban and apixaban. MATERIALS AND METHODS: Low molecular weight heparin calibrated reagent (Siemens Healthineers, Marburg, Germany) was used for anti-FXa activity measurement. Innovance heparin (Siemens Healthineers, Marburg, Germany) calibrated with rivaroxaban and apixaban calibrators (Hyphen BioMed, Neuville-sur-Oise, France) was used for quantitative determination of FXa inhibitors. RESULTS: Analysis showed good agreement between LMWH calibrated and rivaroxaban calibrated activity (κ = 0.76) and very good agreement with apixaban calibrated anti-Xa activity (κ = 0.82), respectively. Low molecular weight heparin anti-FXa activity cut-off values of 0.05 IU/mL and 0.1 IU/mL are suitable for excluding the presence of clinically relevant concentrations (< 30 ng/mL) of rivaroxaban and apixaban, respectively. Concentrations above 300 ng/mL exceeded upper measurement range for LMWH anti-FXa assay and cannot be determined by this method. CONCLUSION: Low molecular weight heparin anti-FXa assay can be used in emergency clinical conditions for ruling out the presence of clinically relevant concentrations of rivaroxaban and apixaban. However, use of LMWH anti-FXa assay is not appropriate for their quantitative determination as an interchangeable method.

Rivaroxaban polymeric amorphous solid dispersions: Moisture-induced thermodynamic phase behavior and intermolecular interactions.

The present study evaluates the physical stability and intermolecular interactions of Rivaroxaban (RXB) amorphous solid dispersions (ASDs) in polymeric carriers via thermodynamic modelling and molecular simulations. Specifically, the Flory-Huggins (FH) lattice solution theory was used to construct thermodynamic phase diagrams of RXB ASDs in four commonly used polymeric carriers (i.e. copovidone, coPVP, povidone, PVP, Soluplus, SOL and hypromellose acetate succinate, HPMCAS), which were stored under 0%, 60% and 75% relative humidity (RH) conditions. In order to verify the phase boundaries predicted by FH modelling (i.e. truly amorphous zone, amorphous-amorphous demixing zones and amorphous-API recrystallization zones), samples of ASDs were examined via polarized light microscopy after storage for up to six months at various RH conditions. Results showed a good agreement between the theoretical and the experimental approaches (i.e. coPVP and PVP resulted in less physically-stable ASDs compared to SOL and HPMCAS) indicating that the proposed FH-based modelling may be a useful tool in predicting long-term physical stability in high humidity conditions. In addition, molecular dynamics (MD) simulations were employed in order to interpret the observed differences in physical stability. Results, which were verified via differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FTIR), suggested the formation of similar intermolecular interactions in all cases, indicating that the interaction with moisture water plays a more crucial role in ASD physical stability compared to the formation of intermolecular interactions between ASD components.

Molecular Basis of Water Sorption Behavior of Rivaroxaban-Malonic Acid Cocrystal.

The present study aims to investigate the molecular basis of water sorption behavior of rivaroxaban-malonic acid cocrystal (RIV-MAL). It was hypothesized, that the amount of water sorbed by a crystalline solid is governed by the surface molecular environment of different crystal facets and their relative abundance to crystal surface. Water sorption behavior was measured using a dynamic vapor sorption analyzer. The surface molecular environment of different crystal facets and their relative contribution were determined using single crystal structure evaluation and face indexation analysis, respectively. The surface area-normalized water sorption for rivaroxaban (RIV), malonic acid (MAL), and RIV-MAL at 90% RH/25 °C was 0.28, 92.6, and 11.1% w/w, respectively. The crystal surface of MAL had a larger contribution (58.7%) of hydrophilic (Hphi) functional groups and showed the "highest" water sorption (92.6% w/w). On the contrary, RIV had a larger surface contribution (65.2%) of hydrophobic (Hpho) functional groups, and the smaller contribution (34.8%) of Hphi+Hpho groups exhibited the "lowest" water sorption (0.28% w/w). The "intermediate" water sorption (11.1% w/w) by RIV-MAL, as compared to RIV, was ascribed to the increased surface contribution of Hphi+Hpho groups (from 34.8 to 42.1%) and reduced hydrophobic surface contribution (from 65.2 to 57.9%). However, the significantly higher water gained (∼39-fold) by the cocrystal as compared to RIV, despite the nominal change in the surface contributions, was further attributed to the relatively stronger hydrogen bonding interactions between the surface-exposed carboxyl groups and water molecules. The study highlights that the amount of water sorbed by the cocrystal is governed by the surface molecular environment and additionally by the strength of hydrogen bonding. This investigation has implications on designing materials with a desired moisture-sorption property.

An unexpected dynamic binding mode between coagulation factor X and Rivaroxaban reveals importance of flexibility in drug binding.

Rivaroxaban (RIV) is a direct oral anticoagulant (DOAC) targeting activated coagulation factor X (FXa). An earlier study reported the F174A mutant of FXa resistant to a RIV-like inhibitor, Apixaban. In current study, the detailed molecular mechanism of the resistance has been explored by molecular dynamics simulations on the impaired interactions between RIV and FXa in the damaged S4 pocket of F174A mutant. Besides, an unexpected relative stable binding mode of S1'S1 was revealed, which required dynamic motions of Gln192 and Gln61 to allow the morpholinone moiety of RIV to shift into the S1' pocket and form strong interactions. These dynamic motions of RIV and critical residues might be important in drug design for direct inhibitors of coagulation factors.

Design of a liquid nano-sized drug delivery system with enhanced solubility of rivaroxaban for venous thromboembolism management in paediatric patients and emergency cases.

The increasing incidence of venous thromboembolism (VTE) in paediatric population has stimulated the development of liquid anticoagulant formulations. Thus our goal is to formulate a liquid formulation of poorly-water soluble anticoagulant, rivaroxaban (RIVA), for paediatric use and to assess the possibility of its intravenous administration in emergencies. Self-nanoemulsifying drug delivery systems (SNEDDSs) were developed and characterized. SNEDDS constituents were estimated from the saturated solubility study followed by plotting the corresponding ternary phase diagrams to determine the best self-emulsified systems. Thermodynamic stability, emulsification, dispersibility, robustness to dilution tests, in vitro dissolution, particle size, and zeta potential were executed to optimize the formulations. The optimized formulation, that composed of Capryol 90:Tween 20:PEG 300 (5:45:50), increased RIVA solubility (285.7-fold than water), it formed nanoemulsion with a particle size of 16.15 nm, PDI of 0.25 and zeta potential of -21.8. It released 100.83 ± 2.78% of RIVA after 5 min. SNEDDS was robust to dilution with oral and parenteral fluids and showed safety to human RBCs. SNEDDS showed enhanced bioavailability after oral and intravenous administration than the oral drug suspension (by 1.25 and 1.26-fold, respectively). Moreover, it exhibited enhanced anticoagulant efficacy in the prevention and treatment of carrageenan-induced thrombosis rat model.

Pharmaceutical diversification via palladium oxidative addition complexes.

Palladium-catalyzed cross-coupling reactions have transformed the exploration of chemical space in the search for materials, medicines, chemical probes, and other functional molecules. However, cross-coupling of densely functionalized substrates remains a major challenge. We devised an alternative approach using stoichiometric quantities of palladium oxidative addition complexes (OACs) derived from drugs or drug-like aryl halides as substrates. In most cases, cross-coupling reactions using OACs proceed under milder conditions and with higher success than the analogous catalytic reactions. OACs exhibit remarkable stability, maintaining their reactivity after months of benchtop storage under ambient conditions. We demonstrated the utility of OACs in a variety of experiments including automated nanomole-scale couplings between an OAC derived from rivaroxaban and hundreds of diverse nucleophiles, as well as the late-stage derivatization of the natural product k252a.

ß-Cyclodextrin-based inclusion complexes and nanocomposites of rivaroxaban for solubility enhancement.

Rivaroxaban (RIV) is an oral anticoagulant used in the prevention of venous thromboembolism in adult patients after total hip replacement or total knee replacement surgery. It is practically insoluble in water and buffer systems (pH 3-9). The present study was aimed to investigate the ß-CD-based inclusion complexes and nanocomposites of rivaroxaban (RIV) for solubility and dissolution enhancement. A novel solubility enhancement approach of inclusion complexation of RIV with ß-CD using spray drying method combined with high pressure homogenization as a particle engineering method was used. Change in crystallinity of RIV nanocomposites was assessed by DSC and PXRD. The interaction of drug with ß-CD was projected through 1H-NMR and FT-IR studies. Saturation solubility and in vitro dissolution study revealed a dramatic increase in solubility and dissolution of RIV, respectively. Thus, spray-dried ß-CD-based nanocomposites could be an innovative approach for solubility and dissolution enhancement of RIV.

FXa-α2-Macroglobulin Complex Neutralizes Direct Oral Anticoagulants Targeting FXa In Vitro and In Vivo.

Increasing number of patients are treated with direct oral anticoagulants (DOAC). An antidote for dabigatran inhibiting thrombin (idarucizumab) is available but no antidote is yet approved for the factor Xa (FXa) inhibitors (xabans). We hypothesized that a complex between Gla-domainless FXa and α2-macroglobulin (GDFXa-α2M) may neutralize the xabans without interfering with normal blood coagulation.Purified α2M was incubated with GDFXa to form GDFXa-α2M. Affinity of apixaban and rivaroxaban for GDFXa-α2M was only slightly decreased compared to FXa. Efficacy and harmlessness of GDFXa-α2M were tested in vitro and in vivo. Stoichiometric excess of GDFXa-α2M neutralized rivaroxaban and apixaban as attested by clot waveform assay and rotational thromboelastometry, whereas GDFXa-α2M alone had no effect on these assays. Efficacy and pro-thrombotic potential of GDFXa-α2M were also assessed in vivo. Half-life of GDFXa-α2M in C57BL6 mice was 4.9 ± 1.1 minutes, but a 0.5 mg/mouse dose resulted in uptake saturation such that 50% persistence was still observed after 170 minutes. Single administration of GDFXa-α2M significantly decreased the rivaroxaban-induced bleeding time (p < 0.001) and blood loss (p < 0.01). GDFXa-α2M did not increase D-dimer or thrombin-antithrombin complex formation, suggesting a lack of pro-thrombotic potential.GDFXa-α2M is therefore an attractive candidate for xaban neutralization neither pro- nor anticoagulant in vitro as well as in vivo.

In vitro dissolution method fitted to in vivo absorption profile of rivaroxaban immediate-release tablets applying in silico data.

OBJECTIVE: This study aimed to develop and validate an in vitro dissolution method based on in silico-in vivo data to determine whether an in vitro-in vivo relationship could be established for rivaroxaban in immediate-release tablets. SIGNIFICANCE: Oral drugs with high permeability but poorly soluble in aqueous media, such as the anticoagulant rivaroxaban, have a major potential to reach a high level of in vitro-in vivo relationship. Currently, there is no study on scientific literature approaching the development of RIV dissolution profile based on its in vivo performance. METHODS AND RESULTS: Drug plasma concentration values were modeled using computer simulation with adjustment of pharmacokinetic properties. Those values were converted into drug fractions absorbed by the Wagner-Nelson deconvolution approach. Gradual and continuous dissolution of RIV tablets was obtained with a 30 rpm basket on 50 mM sodium acetate +0.2% SDS, pH 6.5 medium. Dissolution was conducted for up to 180 min. The fraction absorbed was plotted against the drug fraction dissolved, and a linear point-to-point regression (R2 = 0.9961) obtained. CONCLUSION: The in vitro dissolution method designed promoted a more convenient dissolution profile of RIV tablets, whereas it suggests a better relationship with in vivo performance.

Enhanced Biopharmaceutical Performance of Rivaroxaban through Polymeric Amorphous Solid Dispersion.

Rivaroxaban (RXB) is an orally active direct inhibitor of the activated serine protease Factor Xa, given as monotherapy in the treatment of venous thromboembolism (VTE). It has been characterized in vitro as a substrate for the active, nonsaturable efflux via P-gp transporter, limiting its high permeability. Therefore, the role of P-gp inhibiting polymers in enhancing the biopharmaceutical performance of RXB by preparing polymeric amorphous solid dispersion and subsequent improvement in solubility and permeability was investigated. Initially, solubility parameter and Flory-Huggins interaction parameter were determined for miscibility studies between drug and polymers. Binary dispersions were prepared by dissolving drug with polymers eudragit S100, eudragit L100, and soluplus in common solvent (5% v/v water in tetrahydrofuran) using spray dryer. Prepared binary dispersions were analyzed by differential scanning calorimetry (DSC), microscopy, powder X-ray diffractometry (PXRD), Fourier transform infrared spectroscopy (FTIR), dynamic vapor sorption (DVS), and solution nuclear magnetic resonance (NMR) spectroscopy. Superior performance of binary dispersions was observed upon dissolution and solubility studies over micronized active pharmaceutical ingredient. Amorphous solid dispersion (ASD) prepared with soluplus showed 10-fold increase in apparent solubility and maintenance of supersaturation for 24 h compared to the crystalline RXB. Further, pharmacokinetic study performed in animals was in good correlation with the solubility data. Increases of 5.7- and 6.7-fold were observed in AUC and Cmax, respectively, for ASDs prepared with soluplus compared to those with crystalline RXB. FTIR and NMR spectroscopy unveiled the involvement of N-H group of RXB with C═O group of polymers in intermolecular interactions. The decreased drug efflux ratio was observed for ASDs prepared with eudragit S100 and soluplus in Caco-2 transport study suggesting improvement in the absorption of RXB. Hence, the present study demonstrates ASD using soluplus as a promising formulation strategy for enhancing the biopharmaceutical performance of RXB by increasing the solubility and circumventing the P-gp activity.

Comparison of the effect of the anti-Xa direct oral anticoagulants apixaban, edoxaban, and rivaroxaban on coagulation assays.

INTRODUCTION: The purpose of this study is to compare the effect of increasing concentrations of direct anti-Xa oral anticoagulants (DOAC) apixaban-, edoxaban-, and rivaroxaban-enriched plasma samples on various prothrombin time (PT), activated partial thromboplastin time (APTT), heparin calibrated anti-Xa methods, and other coagulation assays. METHODS: Apixaban, edoxaban, or rivaroxaban was dissolved in dimethylsulfoxide and added to pooled normal plasma to obtain concentrations ranging from 0 ng/mL to approximately 600 ng/mL. The samples were tested using Innovin(®) , Neoplastine(®) CI Plus, Recombiplastin 2G, and Thromborel(®) S for PT testing and Actin, Actin(®) FS, Actin(®) FSL, APTT-Automate, and SynthaSIL for APTT. Samples were also tested using four different anti-Xa methods calibrated for unfractionated heparin or low molecular weight heparin. Special coagulation assays included antithrombin activity, lupus anticoagulant assays, and others. For special coagulation assays, the concentration of DOAC that resulted in a >15% change from baseline value was determined. DOAC quantification was performed using liquid chromatography-tandem mass spectrometry. RESULTS: All PT and APTT reagents demonstrated a higher sensitivity for edoxaban and rivaroxaban than for apixaban. Anti-Xa methods were able to detect low concentrations of DOAC. DOACs effected special coagulation assays to differing degrees, with lupus anticoagulant testing using dilute viper venom, the most sensitive test to the presence of anti-Xa DOAC. CONCLUSION: No PT or APTT reagent system effectively detected apixaban. All anti-Xa methods demonstrated sensitivity to low concentrations of DOAC. Dilute viper venom methods are exquisitely sensitive to anti-Xa DOAC, suggesting potential use of this assay for screening or measuring these drugs.