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Background and Objective: Rivaroxaban is an oral, direct Factor Xa inhibitor, which is at an advanced stage of clinical development for prevention and treatment of thromboembolic disorders. Two phase II studies, ODIXa-DVT and EINSTEIN DVT, assessed the efficacy and safety of oral rivaroxaban (once daily or twice daily) for treatment of acute deep-vein thrombosis (DVT). Population pharmacokinetic and pharmacodynamic analyses of rivaroxaban in patients in these two phase II studies were conducted to characterize the pharmacokinetics/pharmacodynamics of rivaroxaban and the relationship between important patient covariates and model parameters. Exposure simulations in patients with atrial fibrillation (AF) were also performed in order to predict the exposure of rivaroxaban, using modified demographic data reflecting the characteristics of a typical AF population.Methods: A population pharmacokinetic model was developed using plasma samples from these patients. Various simulations were conducted to explore the pharmacokinetics of rivaroxaban in patients with DVT and to predict exposure in those with AF. Correlations between plasma rivaroxaban concentrations and the prothrombin time, Factor Xa activity, HepTest® and activated partial thromboplastin time were also described.Results: The pharmacokinetics of rivaroxaban in patients with DVT were found to be consistent and predictable across all doses studied. The area under the plasma concentration-time curve (AUC) increased dose dependently. The same total daily doses given once daily achieved higher maximum plasma concentration (C(max)) values (∼20%) and lower trough (minimum) plasma concentration (C(trough)) values (∼60%) than when given twice daily; however, the 5th-95th percentile ranges for these parameters overlapped. Rivaroxaban clearance was moderately influenced by age and renal function, and the volume of distribution was influenced by age, body weight and sex; the effects were within the observed interindividual variability. Simulations in virtual patient populations with AF showed that a rivaroxaban dose of 15 mg once daily in patients with creatinine clearance of 30-49 mL/min would achieve AUC and C(max) values similar to those observed with 20 mg once daily in patients with normal renal function. The prothrombin time correlated almost linearly with plasma rivaroxaban concentrations (≤500 μg/L).Conclusion: Population analyses of phase II clinical data indicated that the pharmacokinetics and pharmacodynamics of all rivaroxaban doses were predictable and were affected by expected demographic factors in patients with acute DVT. [ABSTRACT FROM AUTHOR]

Background: There is a clinical need for novel oral anticoagulants with predictable pharmacokinetics and pharmacodynamics. Rivaroxaban is an oral direct Factor Xa (FXa) inhibitor in clinical development for the prevention and treatment of thromboembolic disorders. This analysis was performed to characterize the population pharmacokinetics and pharmacodynamics of rivaroxaban in patients participating in two phase II, double-blind, randomized, active-comparator-controlled studies of twice-daily rivaroxaban for the prevention of venous thromboembolism after total hip- or knee-replacement surgery.Methods: Sparse blood samples were taken from all patients participating in the studies (n = 1009). In addition, a subset of patients in the hip study (n = 36) underwent full profiling. Rivaroxaban plasma concentrations, FXa activity and the prothrombin time were determined. Nonlinear mixed-effects modelling was used to model the population pharmacokinetics and pharmacodynamics of rivaroxaban.Results: An oral one-compartment model described the population pharmacokinetics of rivaroxaban well. On the first postoperative day only, categorization of patients as slow or fast absorbers as a tool to address variability in absorption improved the fit of the model. Clearance of rivaroxaban was lower and more variable on the first postoperative day, and so time was factored into the model. Overall, the only major difference between the models for the hip study and the knee study was that clearance was 26% lower in the knee study, resulting in approximately 30% higher exposure. Residual variability in the models was moderate (37% and 34% in the hip and knee studies, respectively). Plasma concentrations of rivaroxaban increased dose dependently. Pharmacokinetic parameters that were estimated using the models agreed closely with results from full-profile patients in the hip study, demonstrating that rivaroxaban pharmacokinetics are predictable. The pharmacokinetics of rivaroxaban were affected by expected covariates: age affected clearance in the hip study only, haematocrit (on the first postoperative day only) and gender affected clearance in the knee study only, and renal function affected clearance in both studies. Bodyweight affected the volume of distribution in both studies. However, the effects of covariates on the pharmacokinetics of rivaroxaban were generally small, and predictions of 'extreme' case scenarios suggested that fixed dosing of rivaroxaban was likely to be possible. FXa activity and the prothrombin time were both affected by surgery, probably because of perioperative bleeding and intravenous administration of fluids; therefore, time was included in the pharmacodynamic models. In both studies, FXa activity correlated with rivaroxaban plasma concentrations following a maximum effect model, whereas prothrombin time prolongation correlated following a linear model with intercept. The slope of the prothrombin time prolongation correlation was 3.2 seconds/(100 microg/L) in the hip study and 4.2 seconds/(100 microg/L) in the knee study. Both pharmacodynamic models in both studies demonstrated low residual variability of approximately 10%.Conclusion: This population analysis in patients undergoing major orthopaedic surgery demonstrated that rivaroxaban has predictable, dose-dependent pharmacokinetics that were well described by an oral one-compartment model and affected by expected covariates. Rivaroxaban exposure could be assessed using the prothrombin time, if necessary, but not the international normalized ratio. The findings suggested that fixed dosing of rivaroxaban may be possible in patients undergoing major orthopaedic surgery. [ABSTRACT FROM AUTHOR]

Background: Rivaroxaban (BAY 59-7939) is a novel, oral, direct Factor Xa inhibitor in advanced clinical development for the prevention and treatment of thromboembolic disorders. Unwanted pro-arrhythmic effects are a common reason for drugs failing to gain regulatory approval; these properties can be detected by assessing the effect of the drug on the QT interval.Objective: This study was performed, in accordance with International Conference on Harmonisation (ICH) E14 guidance, to assess whether rivaroxaban prolongs the QT interval.Study Design: This was a prospective, randomized, double-blind, double-dummy, four-way crossover study.Setting: The study was conducted at a clinical pharmacology research unit.Subjects: Healthy male and female subjects (n = 54) aged > or =50 years were enrolled and remained in the study unit for 3 days for each treatment. Of these, 50 patients were eligible for the QT analysis.Intervention: Subjects received single oral doses of rivaroxaban 45 mg or 15 mg, moxifloxacin 400 mg (positive control), or placebo.Outcome Measures: Multiple ECGs were taken at frequent intervals after drug administration, and the QT interval was measured manually under blinded conditions at a central laboratory. The Fridericia correction formula (QTcF) was used to correct the QT interval for heart rate. The primary outcome was the effect of rivaroxaban or moxifloxacin on the placebo-subtracted QTcF 3 hours after administration. The frequency of outlying QTcF values and the tolerability of the treatments were also assessed.Results: All treatments were well tolerated and had no effect on heart rate. Moxifloxacin established the required assay sensitivity; placebo-subtracted QTcF 3 hours after moxifloxacin administration was prolonged by 9.77 ms (95% CI 7.39, 12.15). Placebo-subtracted QTcF values 3 hours after rivaroxaban administration were -0.91 ms (95% CI -3.33, 1.52) and -1.83 ms (95% CI -4.19, 0.54) with rivaroxaban 45 mg and 15 mg, respectively. QTcF was not prolonged with rivaroxaban at any time, and the frequency of outlying results with rivaroxaban and placebo was similar.Conclusion: This thorough QT study, which was performed in accordance with ICH E14 guidelines, shows that rivaroxaban does not prolong the QTc interval. Therefore, the potential of rivaroxaban for the prevention and treatment of thromboembolic disorders, including chronic cardiovascular disorders, can be investigated in appropriate clinical studies without the need for intensive monitoring of the QTc interval. [ABSTRACT FROM AUTHOR]

Anticoagulants are often dose adjusted, or their use restricted, in patients with extremes of body weight. Rivaroxaban (BAY 59-7939) is a novel, oral, direct factor Xa inhibitor in clinical development. This was a randomized, single-blind, placebo-controlled, parallel-group study in healthy male and female subjects to assess the effect of extreme body weight (120 kg), and gender, on the safety, tolerability, pharmacokinetics, and pharmacodynamics of rivaroxaban 10 mg, compared with subjects of normal weight (70-80 kg). Rivaroxaban was well tolerated. C(max) of rivaroxaban was unaffected in subjects >120 kg but was increased by 24% in subjects weighing

Rivaroxaban (BAY 59-7939) is an oral, direct Factor Xa inhibitor in advanced clinical development for the prevention and treatment of thromboembolic disorders. This was a randomized, 2-way crossover study in healthy male subjects, with an aspirin run-in period, to examine whether aspirin influences the safety, tolerability, pharmacodynamics, and pharmacokinetics of rivaroxaban. All treatments were well tolerated; drug-related adverse events were mild and transient. Aspirin did not alter the effects of rivaroxaban on Factor Xa activity or clotting tests. Platelet aggregation and bleeding time were not affected by rivaroxaban, and rivaroxaban did not influence the effects of aspirin on these parameters to a clinically relevant extent. Aspirin did not affect the pharmacokinetics of rivaroxaban, including the fraction unbound. This study suggests that there is no clinically relevant interaction between rivaroxaban and aspirin and that the 2 drugs could be administered concomitantly at the doses used in this study. [ABSTRACT FROM AUTHOR]

To investigate the influence of food and administration of an antacid (aluminum-magnesium hydroxide) or ranitidine on the absorption of BAY 59-7939 (rivaroxaban), 4 randomized studies were performed in healthy male subjects. In 2 food interaction studies, subjects received BAY 59-7939, either as two 5-mg tablets (fasted and fed), four 5-mg tablets (fasted), or one 20-mg tablet (fasted and fed). In 2 drug interaction studies, BAY 59-7939 (six 5-mg tablets) was given alone or with ranitidine (150 mg twice daily, preceded by a 3-day pretreatment phase) or antacid (10 mL). Plasma samples were obtained to assess pharmacokinetic and pharmacodynamic parameters of BAY 59-7939. In the presence of food, time to maximum concentration (t(max)) was delayed by 1.25 hours; maximum concentration (C(max)) and area under the curve (AUC) were increased, with reduced interindividual variability at higher doses of BAY 59-7939. Compared with baseline, BAY 59-7939 resulted in a relative increase in maximum prothrombin time (PT) prolongation of 44% (10 mg) and 53% (20 mg) in the fasted state, compared with 53% and 83% after food. Time to maximum PT prolongation was delayed by 0.5 to 1.5 hours after food, with no relevant influence of food type. No significant difference in C(max) and AUC was observed with coadministration of BAY 59-7939 and ranitidine or antacid. [ABSTRACT FROM AUTHOR]

Purpose: To characterize the safety, pharmacodynamics, and pharmacokinetics (PK) of vericiguat in healthy males., Methods: Six phase I studies were conducted in European, Chinese, and Japanese males. Subjects received oral vericiguat as a single dose (0.5-15.0 mg solution [for first-in-human study] or 1.25-10.0 mg immediate release [IR tablets]) or multiple doses (1.25-10.0 mg IR tablets once daily [QD] or 5.0 mg IR tablets twice daily for 7 consecutive days). Bioavailability and food effects on vericiguat PK (IR tablets) were also studied in European subjects., Results: Overall, 255 of 265 randomized subjects completed their respective studies. There were no deaths or serious adverse events. Vericiguat was generally well tolerated at doses ≤ 10.0 mg. In the first-in-human study, the most frequent drug-related adverse events were headache and postural dizziness (experienced by five subjects each [7.2%]). Three of four subjects who received vericiguat 15.0 mg (oral solution, fasted) experienced orthostatic reactions. Vericiguat (≤ 10.0 mg, IR tablets) was rapidly absorbed (median time to reach maximum plasma concentration ≤ 2.5 h [fasted]) with a mean half-life of about 22.0 h (range 17.9-27.0 h for single and multiple doses). No evidence for deviation from dose proportionality or unexpected accumulation was observed. Administration of vericiguat 5.0 mg IR tablets with food increased bioavailability by 19% (estimated ratio 119% [90% confidence interval]: 108; 131]), reduced PK variability, and prolonged vericiguat absorption relative to the fasted state., Conclusion: In general, vericiguat was well tolerated. These results supported further clinical evaluation of vericiguat QD in patients with heart failure., Registry Numbers: EudraCT: 2011-001627-21; EudraCT: 2012-000953-30.

Background: Vericiguat is a stimulator of soluble guanylate cyclase currently under investigation as a first-in-class therapy for worsening chronic heart failure (NCT02861534). Patients with heart failure often require polypharmacy because of comorbidities. Hence, understanding the clearance mechanisms, elimination, and potential for pharmacokinetic drug-drug interactions of vericiguat is important for dose recommendations in this patient population., Methods: Biotransformation and perpetrator properties of vericiguat were characterized in vitro using human hepatocytes, liver microsomes, and recombinant enzymes. This was complemented by a human mass balance study and ten drug-drug interaction studies in healthy volunteers wherein vericiguat was co-administered orally with omeprazole, magnesium/aluminum hydroxide, ketoconazole, rifampicin, mefenamic acid, midazolam, warfarin, digoxin, sacubitril/valsartan, aspirin, or sildenafil., Results: In the human mass balance study, mean total radioactivity recovered was 98.3% of the dose administered (53.1% and 45.2% excreted via urine and feces, respectively). The main metabolic pathway of vericiguat is glucuronidation via uridine diphosphate-glucuronosyltransferase 1A9 and 1A1. In vitro studies revealed a low risk of vericiguat acting as a perpetrator by inhibiting cytochrome P450s, uridine diphosphate-glucuronosyltransferase isoforms, or major transport proteins, or by inducing cytochrome P450s. These observations were supported by phase I drug-drug interaction studies. Phase I studies that assessed the propensity of vericiguat as a victim drug showed changes in the range that did not warrant recommendations for dose adjustment in phase III., Conclusions: A low pharmacokinetic interaction potential of vericiguat was estimated from in vitro data and confirmed in vivo. Thus, vericiguat is suitable for a patient population with multiple comorbidities requiring polypharmacy.

Anticoagulant plasma concentrations and patient characteristics might affect the benefit-risk balance of therapy. The study objective was to assess the impact of model-predicted rivaroxaban exposure and patient characteristics on outcomes in patients receiving rivaroxaban for venous thromboembolism (VTE) prophylaxis (VTE-P) after hip/knee replacement surgery. Post hoc exposure-response analyses were conducted using data from the phase 3 RECORD1-4 studies, in which 12,729 patients were randomized to rivaroxaban 10 mg once daily or enoxaparin for ≤ 39 days. Multivariate regression approaches were used to correlate model-predicted individual rivaroxaban exposures and patient characteristics with outcomes. In the absence of measured rivaroxaban exposure, exposure estimates were predicted based on individual increases in prothrombin time (PT) and by making use of the known correlation between rivaroxaban plasma concentration and dynamics of PT. No significant associations between rivaroxaban exposure and total VTE or major bleeding were identified. A significant association between exposure and a composite of major or non-major clinically relevant (NMCR) bleeding from day 4 after surgery was observed. The relationship was shallow, with an approximate predicted absolute increase in a composite of major or NMCR bleeding from 1.08 [95% confidence interval (CI) 0.76-1.54] to 2.18% (95% CI 1.51-3.17) at the 5th and 95th percentiles of trough plasma concentration, respectively. In conclusion, based on the underlying data and analysis, no reliable target window for exposure with improved benefit-risk could be identified within the investigated exposure range. Hence, monitoring rivaroxaban levels is unlikely to be beneficial in VTE-P.

Anticoagulant plasma concentrations and patient characteristics might affect the benefit-risk balance of therapy. This study assessed the impact of model-predicted rivaroxaban exposure and patient characteristics on outcomes in patients receiving rivaroxaban for venous thromboembolism treatment (VTE-T) using data from the phase 3 EINSTEIN-DVT and EINSTEIN-PE studies. In the absence of measured rivaroxaban exposure, exposure estimates were predicted based on individual increases in prothrombin time (PT) and the known correlation between rivaroxaban plasma concentrations and PT dynamics. The composite efficacy outcomes evaluated were recurrent deep-vein thrombosis (DVT) and pulmonary embolism (PE) and recurrent DVT, PE and all-cause death; safety outcomes were major bleeding and the composite of major or non-major clinically relevant (NMCR) bleeding. Exposure-response relationships were evaluated using multivariate logistic and Cox regression for the twice-daily (BID) and once-daily (OD) dosing periods, respectively. Predicted rivaroxaban exposure and CrCl were significantly associated with both efficacy outcomes in the BID period. In the OD period, exposure was significantly associated with recurrent DVT and PE but not recurrent DVT, PE and all-cause death. The statistically significant exposure-efficacy relationships were shallow. Exposure-safety relationships were absent within the investigated exposure range. During both dosing periods, low baseline hemoglobin and prior bleeding were associated with the composite of major or NMCR bleeding. In conclusion, based on the underlying data and analysis, no reliable target window for exposure with improved benefit-risk could be identified within the investigated exposure range. Therefore, monitoring rivaroxaban levels is unlikely to be beneficial in VTE-T.

Prothrombin time (PT) is a measure of coagulation status and was assessed in the majority of patients in the rivaroxaban phase II and III clinical trials as a pharmacodynamic marker. In the absence of sufficient phase III pharmacokinetic (PK) data to provide individual exposure measures for input into rivaroxaban exposure-response analyses, the aim of the present study was to investigate the use of PT-adjustment approaches (i.e., the use of observed individual PT measurements) to enhance the prediction of individual rivaroxaban exposure metrics (derived using a previously developed integrated population PK model) based on the observed linear relationship between PT and rivaroxaban plasma concentrations. The PT-adjustment approaches were established using time-matched PK and PT measurements, which were available from 1,779 patients across four phase II trials and one phase III trial of rivaroxaban. PT-adjusted exposure estimates improved the identification of statistically significant effects when compared with covariate-only exposure estimates., (© 2019 Bayer CPT: Pharmacometrics & Systems Pharmacology published by Wiley Periodicals, Inc. on behalf of the American Society for Clinical Pharmacology and Therapeutics.)

Riociguat, a first-in-class soluble guanylate cyclase stimulator, is approved for the treatment of pulmonary arterial hypertension (PAH), a serious potential complication of human immunodeficiency virus (HIV) infection. This open-label study investigated the pharmacokinetic drug-drug interaction potential of antiretroviral therapies on riociguat exposure in HIV-infected adults. HIV-infected adults without PAH on stable antiretroviral regimens (efavirenz/emtricitabine/tenofovir disoproxil, emtricitabine/rilpivirine/tenofovir disoproxil, elvitegravir/cobicistat/emtricitabine/tenofovir disoproxil, abacavir/dolutegravir/lamivudine, or a ritonavir-boosted triple regimen) for ≥ 6 weeks received a single riociguat dose (0.5 mg). Riociguat pharmacokinetics and safety were assessed; pharmacokinetics was compared with historical healthy volunteer data. Of 41 participants treated (n = 8 in each arm, except n = 9 in the ritonavir-boosted triple regimen arm), 40 were included in the pharmacokinetic analyses. Riociguat median t max was 1.00-1.27 h, with comparable maximum concentration (C max ) across the five background antiretroviral groups. Riociguat exposure was highest with abacavir/dolutegravir/lamivudine, followed by elvitegravir/cobicistat/emtricitabine/tenofovir disoproxil > emtricitabine/rilpivirine/tenofovir disoproxil > ritonavir-boosted triple regimen > efavirenz/emtricitabine/tenofovir disoproxil; riociguat area under the plasma concentration versus time curve (AUC) was approximately threefold higher with abacavir/dolutegravir/lamivudine than efavirenz/emtricitabine/tenofovir disoproxil. Compared with historical data, riociguat exposure in HIV-infected adults was similar when co-administered with efavirenz/emtricitabine/tenofovir disoproxil, slightly increased when administered with ritonavir-boosted triple regimen and increased by approximately threefold when administered with abacavir/dolutegravir/lamivudine. Riociguat was well tolerated, with no new safety findings. Riociguat was well tolerated in adults with HIV on stable background antiretroviral therapy although an apparent increase in AUC of riociguat was observed in patients receiving abacavir/dolutegravir/lamivudine. Patients should be monitored closely during riociguat initiation and dose adjustment for signs and symptoms of hypotension.

The population pharmacokinetics (PK) of rivaroxaban have been evaluated in several population-specific models. We developed an integrated population PK model using pooled data from 4,918 patients in 7 clinical trials across all approved indications. Effects of gender, age, and weight on apparent clearance (CL/F) and apparent volume of distribution (V/F), renal function, and comedication on CL/F, and relative bioavailability as a function of dose (F) were analyzed. Virtual subpopulations for exposure simulations were defined by age, creatinine clearance (CrCL) and body mass index (BMI). Rivaroxaban PK were adequately described by a one-compartment disposition model with a first-order absorption rate constant. Significant effects of CrCL, use of comedications, and study population on CL/F, age, weight, and gender on V/F, and dose on F were identified. CrCL had a modest influence on exposure, whereas age and BMI had a minor influence. The model was suitable to predict rivaroxaban exposure in patient subgroups of special interest., (© 2018 The Authors CPT: Pharmacometrics & Systems Pharmacology published by Wiley Periodicals, Inc. on behalf of American Society for Clinical Pharmacology and Therapeutics.)

Aims: Food intake is known to have various effects on gastrointestinal luminal conditions in terms of transit times, hydrodynamic forces and/or luminal fluid composition and can therefore affect the dissolution behavior of solid oral dosage forms. The aim of this study was to investigate and detect the dosage form-dependent food effect that has been observed for two extended-release formulations of nifedipine using in vitro dissolution tests., Methods: Two monolithic extended release formulations, the osmotic pump Adalat® XL 60mg and matrix-type Adalat® Eins 30mg formulation, were investigated with biorelevant dissolution methods using the USP apparatus III and IV under both simulated prandial states, and their corresponding quality control dissolution method. In vitro data were compared to published and unpublished in vivo data using deconvolution-based in vitro - in vivo correlation (IVIVC) approaches., Results: Quality control dissolution methods tended to overestimate the dissolution rate due to the excessive solubilizing capabilities of the sodium dodecyl sulfate (SDS)-containing dissolution media. Using Level II biorelevant media the dosage form dependent food effect for nifedipine was described well when studied with the USP apparatus III, whereas the USP apparatus IV failed to detect the positive food effect for the matrix-type dosage form., Conclusions: It was demonstrated that biorelevant methods can serve as a useful tool during formulation development as they were able to qualitatively reflect the in vivo data., (Copyright © 2016 Elsevier B.V. All rights reserved.)

The purpose of the study was to experimentally deduce pH-dependent critical volumes to dissolve applied dose (VDAD) that determine whether a drug candidate can be developed as immediate release (IR) tablet containing crystalline API, or if solubilization technology is needed to allow for sufficient oral bioavailability. pH-dependent VDADs of 22 and 83 compounds were plotted vs. the relative oral bioavailability (AUC solid vs. AUC solution formulation, Frel) in humans and rats, respectively. Furthermore, in order to investigate to what extent Frel rat may predict issues with solubility limited absorption in human, Frel rat was plotted vs. Frel human. Additionally, the impact of bile salts and lecithin on in vitro dissolution of poorly soluble compounds was tested and data compared to Frel rat and human. Respective in vitro - in vivo and in vivo - in vivo correlations were generated and used to build developability criteria. As a result, based on pH-dependent VDAD, Frel rat and in vitro dissolution in simulated intestinal fluid the IR formulation strategy within Pharmaceutical Research and Development organizations can be already set at late stage of drug discovery., (Copyright © 2016 Elsevier B.V. All rights reserved.)

Riociguat is the first oral soluble guanylate cyclase stimulator shown to improve pulmonary hemodynamics in patients with pulmonary arterial hypertension and chronic thromboembolic pulmonary hypertension (PH). This pilot study assessed the impact of a single dose of riociguat on hemodynamics, gas exchange, and lung function in patients with PH associated with chronic obstructive pulmonary disease (COPD). Adults with COPD-associated borderline or manifest PH (pulmonary vascular resistance > 270 dyn·s·cm(-5), mean pulmonary artery pressure ≥ 23 mmHg, ratio of forced expiratory volume in 1 second [FEV1] to forced vital capacity < 70%, and partial pressure of oxygen and carbon dioxide in arterial blood > 50 and ≤ 55 mmHg, respectively) received riociguat 1 or 2.5 mg during right heart catheterization. Twenty-two patients completed the study (11 men, 11 women, aged 56-82 years; 1-mg group: n = 10 [mean FEV1: 43.1%]; 2.5-mg group: n = 12 [mean FEV1: 41.2%]). Riociguat caused significant improvements (P < 0.01) from baseline in mean pulmonary artery pressure (1 mg: -3.60 mmHg [-11.44%]; 2.5 mg: -4.83 mmHg [-14.76%]) and pulmonary vascular resistance (1 mg: -58.32 dyn·s·cm(-5) [-15.35%]; 2.5 mg: -123.8 dyn·s·cm(-5) [-32.96%]). No relevant changes in lung function or gas exchange were observed. Single doses of riociguat were well tolerated and showed promising hemodynamic effects without untoward effects on gas exchange or lung function in patients with COPD-associated PH. Placebo-controlled studies of chronic treatment with riociguat are warranted.

Recently, the European Medicines Agency (EMA) published the new draft guideline on the pharmacokinetic and clinical evaluation of modified release (MR) formulations. The draft guideline contains the new requirement of performing multiple dose (MD) bioequivalence studies, in the case when the MR formulation is expected to show 'relevant' drug accumulation at steady state (SS). This new requirement reveals three fundamental issues, which are discussed in the current work: first, measurement for the extent of drug accumulation (MEDA) predicted from single dose (SD) study data; second, its relationship with the percentage residual area under the plasma concentration-time curve (AUC) outside the dosing interval (τ) after SD administration, %AUC(τ-∞)SD ; and third, the rationale for a threshold of %AUC(τ-∞)SD that predicts 'relevant' drug accumulation at SS. This work revealed that the accumulation ratio RA,AUC , derived from the ratio of the time-averaged plasma concentrations during τ at SS and after SD administration, respectively, is the 'preferred' MEDA for MR formulations. A causal relationship was derived between %AUC(τ-∞)SD and RA,AUC , which is valid for any drug (product) that shows (dose- and time-) linear pharmacokinetics regardless of the shape of the plasma concentration-time curve. Considering AUC thresholds from other guidelines together with the causal relationship between %AUC(τ-∞)SD and RA,AUC indicates that values of %AUC(τ-∞)SD ≤ 20%, resulting in RA,AUC ≤ 1.25, can be considered as leading to non-relevant drug accumulation. Hence, the authors suggest that 20% for %AUC(τ-∞)SD is a reasonable threshold and selection criterion between SD or MD study designs for bioequivalence studies of new MR formulations., (© 2014 The Authors Biopharmaceutics & Drug Disposition Published by John Wiley & Sons Ltd.)

The long-lasting anticoagulant effect of vitamin K antagonists can be problematic in cases of adverse drug reactions or when patients are switched to another anticoagulant therapy. The objective of this study was to examine in silico the anticoagulant effect of rivaroxaban, an oral, direct Factor Xa inhibitor, combined with the residual effect of discontinued warfarin. Our simulations were based on the recommended anticoagulant dosing regimen for stroke prevention in patients with atrial fibrillation. The effects of the combination of discontinued warfarin plus rivaroxaban were simulated using an extended version of a previously validated blood coagulation computer model. A strong synergistic effect of the two distinct mechanisms of action was observed in the first 2-3 days after warfarin discontinuation; thereafter, the effect was close to additive. Nomograms for the introduction of rivaroxaban therapy after warfarin discontinuation were derived for Caucasian and Japanese patients using safety and efficacy criteria described previously, together with the coagulation model. The findings of our study provide a mechanistic pharmacologic rationale for dosing schedules during the therapy switch from warfarin to rivaroxaban and support the switching strategies as outlined in the Summary of Product Characteristics and Prescribing Information for rivaroxaban.

Rivaroxaban is an oral, direct Factor Xa inhibitor that targets free and clot-bound Factor Xa and Factor Xa in the prothrombinase complex. It is absorbed rapidly, with maximum plasma concentrations being reached 2-4 h after tablet intake. Oral bioavailability is high (80-100 %) for the 10 mg tablet irrespective of food intake and for the 15 mg and 20 mg tablets when taken with food. Variability in the pharmacokinetic parameters is moderate (coefficient of variation 30-40 %). The pharmacokinetic profile of rivaroxaban is consistent in healthy subjects and across a broad range of different patient populations studied. Elimination of rivaroxaban from plasma occurs with a terminal half-life of 5-9 h in healthy young subjects and 11-13 h in elderly subjects. Rivaroxaban produces a pharmacodynamic effect that is closely correlated with its plasma concentration. The pharmacokinetic and pharmacodynamic relationship for inhibition of Factor Xa activity can be described by an E max model, and prothrombin time prolongation by a linear model. Rivaroxaban does not inhibit cytochrome P450 enzymes or known drug transporter systems and, because rivaroxaban has multiple elimination pathways, it has no clinically relevant interactions with most commonly prescribed medications. Rivaroxaban has been approved for clinical use in several thromboembolic disorders.