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The molar solubility of bosentan (BST) in mixtures of ethylene glycol (EG) + water at different temperatures from 293.15 to 313.15 K was measured by using the shake flask technique. Experimental solubility increased with increasing temperature and mass fraction of cosolvent; so that, the largest solubility was found in neat cosolvent at 313.15 K. The cosolvency models of Jouyban–Acree and its combined version with van't Hoff equation (Jouyban–Acree–van't Hoff model) were used for correlation of BST solubility data with the low values of mean relative deviations (MRD% ≤ 8.1). Furthermore, some untested data were predicted based on the achieved trained models at 298.15 K. X-ray powder diffraction was also served to analyze the equilibrium solid phase crystal of BST and the results turns out that no polymorphic transformation, solvate formation or crystal transition during the whole solvent crystallization process. [ABSTRACT FROM AUTHOR]

Although there are rapid developments in molecular science and synthetic chemistry for investigation of many essential drug molecules, poor solubility and bioavailability issues are major constraint in the design of more efficient formulations. This research study focuses on the enhancement of solubility and development of the bucco-adhesive drug delivery system of bosentan using Soluplus® (polyvinyl-caprolactam-polyvinyl-acetate-polyethylene glycol graft co-polymer) as a carrier. A 32-factorial design was implemented to develop bucco-adhesive tablets using hydroxypropyl methyl cellulose (HPMC) K100 LV (X1) and Carbopol 934 P (X2) as independent variables at various levels whereas t50%(Y1) (time required to release 50% of drug), Rel4h (Y2) (percentage of the drug release in 4 h) and bio-adhesive strength (Y3) were considered as set response parameters. The positive effect of the surface response quadratic model demonstrated the change in the already set dependent variables of t50%, Rel4h and bio-adhesive strength. The FT-IR study confirmed the suitability of all the components used in the design of formulation. DSC and XRD study have confirmed the encapsulation of bosentan in the Soluplus® carrier and amorphous form of bosentan, respectively. Overall, 6.832-fold increase in solubility was observed for bosentan-solid dispersion. High-water uptake and swelling of bucco-adhesive tablets (containing bosentan-solid dispersion) was observed due to presence of the highly hydrophilic-Soluplus®. Rel4hwas found to be 97.86 ± 0.57% for optimized formulation (F4) and was decreased with increasing polymer content. The values of t50% were found to be enhanced from 1.11 to 2.32 h at the lower to higher levels of both the polymers respectively. [ABSTRACT FROM AUTHOR]

Pulmonary artery hypertension (PAH) is a common and serious disease which is characterized by pulmonary vascular remodeling. Bosentan (BST) is the first approved oral targeted drug of endothelin-1 (ET-1) receptor antagonists for the treatment of PAH. MicroRNA-27a (miR-27a) and peroxisome proliferator-activated receptor γ (PPARγ) were found to be related to the pathogenesis of PAH. To further explore the signal transduction mechanism of BST in the treatment of PAH, we examined the effects of BST on endothelin receptors, miR-27a, and PPARγ. Meanwhile, the influence of miR-27a in the formation and development of PAH was discussed. Our results demonstrated that during the pathophysiology of PAH, miR-27a, PPARγ, and ET-1 were cross-inhibited, which indicated that the miR-27a/PPARγ/ET-1 signaling pathway was dysregulated; in addition, BST could competitively bind to ET-1 receptors and inhibit the miR-27a/PPARγ/ET-1 signaling pathway, thereby delaying the proliferation of PASMCs and affecting the development of PAH. Our results give a new understanding of the pathogenesis and treatment of PAH and provide more reliable evidence for the application of BST in the treatment of PAH in the clinic. [ABSTRACT FROM AUTHOR]

Arsenic exposure is well documented to cause serious health hazards, such as cardiovascular abnormalities, neurotoxicity and nephrotoxicity. In the present study, we intended to explore the role of bosentan, an endothelial receptor antagonist, against sodium arsenite-induced nephrotoxicity and hepatotoxicity in rats. Sodium arsenite (5 mg/kg, oral) was administered for 4 weeks to induce renal dysfunction in rats. Sodium arsenite intoxicated rats were treated with bosentan (50 and 100 mg/kg, oral) for 4 weeks. Arsenic led renal damage was demonstrated by significant increase in serum creatinine, urea, uric acid, potassium, fractional excretion of sodium, microproteinuria and decreased creatinine clearance in rats. Sodium arsenite resulted in marked oxidative stress in rat kidneys as indicated by profound increase in lipid peroxides, and superoxide anion generation alongwith decrease in reduced glutathione levels. Hydroxyproline assay highlighted arsenic-induced renal fibrosis in rats. Hematoxylin-eosin staining indicated glomerular and tubular changes in rat kidneys. Picrosirius red staining highlighted collagen deposition in renal tissues of arsenic treated rats. Immunohistological results demonstrated the reduction of renal eNOS expression in arsenic treated rats. Notably, treatment with bosentan attenuated arsenic-induced renal damage and resisted arsenic-led reduction in renal eNOS expression. In addition, sodium arsenite–induced alteration in hepatic parameters (serum aspartate aminotransferase, alanine transferase, alkaline phosphatase, bilirubin), oxidative stress and histological changes were abrogated by bosentan treatment in rats. Hence, we conclude that bosentan treatment attenuated sodium arsenite–induced oxidative stress, fibrosis and reduction in renal eNOS expression in rat kidneys. Moreover, bosentan abrogated arsenic led hepatic changes in rats. [ABSTRACT FROM AUTHOR]

Hemolytic anemia is a very important immune-mediated reaction, which its late diagnosis can be fatal. Medications along with other causes can induce hemolytic anemia. Drug induced immune hemolytic anemia (DIIHA) is caused by the development of autoantibodies. Accordingly, DIIHA is rare and there is not enough data for its prevalence. Number of drugs that can cause DIIHA have increased in recent decades. A 17-year-old man who had congenital single ventricle heart (CHB) and pulmonary artery hypertension (PAH) was admitted at Imam Khomeini hospital complex affiliated to Tehran University of Medical Sciences, with chief complaint of jaundice and icter. Bosentan and Tadalafil were in the list of the drugs used by this patient. Although both drugs were recommended to be discontinued in the patient, in the course of hospitalization, the patient accidentally continued to take his Tadalafil. However, the patient's recovery continued. Given that the patient's Coombs test was positive, his hemolytic anemia mechanism was drug-induced immune-mediated hemolytic anemia. As a result, according to Naranjo score = 6, Bosentan was considered as the main possible culprit to induce DIIHA in this patient. Following the discontinuation of Bosentan and receiving Prednisolone, the patient's clinical symptoms and laboratory parameters resolved and the patient was then discharged. [ABSTRACT FROM AUTHOR]

Purpose: Bosentan, clazosentan, and tezosentan are three small-molecule endothelin receptor antagonists (ERAs), displacing endothelin-1 (ET-1) from its binding site. A target-mediated drug disposition (TMDD) pharmacokinetic (PK) model described the non-linearity in the PK of bosentan caused by its high receptor binding affinity with time-dependent varying receptor expression or reappearance. The aim of this analysis was to investigate the presence of TMDD for clazosentan and tezosentan and to corroborate the hypothesis of a diurnal receptor synthesis. Methods: PK data from healthy subjects after intravenous (i.v.) administration of single ascending doses of bosentan, clazosentan, and tezosentan were analyzed. Frequent blood samples for PK measurements were collected. Population analyses, simulations, and evaluations were performed using a non-linear mixed-effects modeling approach. Results: Two-compartment TMDD models were successfully developed describing the PK of all three ERAs with different receptor-complex internalization properties. The observed multiple peaks in the concentration-time profiles were captured with cosine functions on the receptor synthesis rate mimicking a diurnal receptor expression or reappearance. The results strongly suggest that TMDD is a class effect of ERAs. Conclusion: The developed TMDD PK models are a next step towards understanding the complex PK of ERAs and further support the hypothesis that TMDD is a class effect of ERAs. [ABSTRACT FROM AUTHOR]

Objective: Research comparing bosentan and macitentan in chronic thromboembolic pulmonary hypertension (CTEPH) is scarce, although macitentan might have superior pharmacologic properties. We present the first real-world, 2-year follow-up results and compare clinical outcomes of both drugs in CTEPH. Methods: All consecutive, technical inoperable or residual CTEPH patients receiving bosentan or macitentan, diagnosed in our multidisciplinary team between January 2003 and January 2019, were included. We report and compare survival, clinical worsening (CW), adverse events, WHO FC, NT-proBNP and 6-min walking test (6MWT) until 2 years after medication initiation. Results: In total, 112 patients receiving bosentan or macitentan (58% female, mean age 62 ± 14 years, 68% WHO FC III/IV, 51% bosentan) could be included. Mean treatment duration was 1.9 ± 0.4 years for bosentan and 1.2 ± 0.6 years for macitentan. Two-year survival rate was 91% for bosentan and 80% for macitentan (HR mortality macitentan 1.85 [0.56–6.10], p = 0.31). Two-year CW-free survival was 81% and 58%, respectively (HR CW macitentan 2.16 [0.962–4.87], p = 0.06). Right atrial pressure, cardiac output (for mortality alone) and 6MWT lowest saturation were multivariate predictors at baseline. Overall adverse event rates were comparable and WHO FC, NT-proBNP and 6MWT distance improved similar for both drugs till 2-year follow-up. Conclusion: CTEPH patients receiving bosentan or macitentan have improved clinical outcomes till 2-year follow-up, without significant differences in outcomes between both therapies. [ABSTRACT FROM AUTHOR]

Abstract: Oxygen plays a central role in cardiac energy metabolism. At high altitude where the ambient oxygen level is low, we found EDNRB is associated with human hypoxia adaptation. Our subsequent study in global heterozygous knockout mice (Ednrb−/+) revealed that cardiac function was conserved in these mice when exposed to extreme hypoxia. The major goal of this study was (i) to determine the functional role of cardiomyocyte EdnrB in maintaining cardiac function under hypoxic stress and (ii) to validate the phenotypes we detected in Ednrb−/+ mice using EDNRB blockers. Unlike the global knockouts, cardiac-specific heterozygote (EdnrBflox/+) and homozygote (EdnrBflox/flox) EdnrB knockout mice were phenotypically normal. When treated with graded low levels of oxygen (10% and 5% O2), both EdnrBflox/+ and EdnrBflox/flox were hypoxia tolerant. The cardiac indexes at 10% and 5% O2 for EdnrBflox/+ were significantly higher and lactate levels were significantly lower when compared to the cre-negative controls (P < 0.05). Simultaneously, mice treated with BQ-788 (EDNRB-specific blocker) had a significantly higher cardiac index (P < 0.005) and significantly lower lactate levels (P < 0.0001) than in control mice. A similar result was obtained with mice treated with Bosentan (non-specific). These data indicate that a lower level or complete lack of EdnrB in the cardiomyocytes significantly improves cardiac performance under extreme hypoxia, a novel role of cardiomyocyte EdnrB in the regulation of cardiac function. Furthermore, this rescue under extreme hypoxia can also be achieved using EDNRB-specific pharmacological agents, e.g., BQ-788. This systematically confirms, both genetically and pharmacologically, the protective role of a lower EDNRB under extreme hypoxia stress.Key messages: Under normal condition, cardiomyocytes-specific EdnrB knockout mice, both heterozygote and homozygote, are phenotypically normal.Under hypoxic condition, a lower level or complete deletion of cardiomyocyte EdnrB conserves cardiac function by maintaining high cardiac index.Similarly, mice treated with both specific (BQ-788) and non-specific (Bosentan) EDNRB blockers are tolerant to hypoxia by maintaining better cardiac function.The oxygen perfusion under extreme hypoxia is better in the mice with lower EDNRB, as depicted by lower lactate level at 5% oxygen.Our current study systematically confirms, both genetically and pharmacologically, the protective role of a lower EDNRB under extreme hypoxia stress.Overall, it supports our hypothesis that studies on human hypoxia adaptation provide new insight to common disease pathogenesis and treatments. [ABSTRACT FROM AUTHOR]

Bosentan is well known to induce cholestatic liver toxicity in humans. The present study was set up to characterize the hepatotoxic effects of this drug at the transcriptomic, proteomic, and metabolomic levels. For this purpose, human hepatoma-derived HepaRG cells were exposed to a number of concentrations of bosentan during different periods of time. Bosentan was found to functionally and transcriptionally suppress the bile salt export pump as well as to alter bile acid levels. Pathway analysis of both transcriptomics and proteomics data identified cholestasis as a major toxicological event. Transcriptomics results further showed several gene changes related to the activation of the nuclear farnesoid X receptor. Induction of oxidative stress and inflammation were also observed. Metabolomics analysis indicated changes in the abundance of specific endogenous metabolites related to mitochondrial impairment. The outcome of this study may assist in the further optimization of adverse outcome pathway constructs that mechanistically describe the processes involved in cholestatic liver injury. [ABSTRACT FROM AUTHOR]

The study provides the physicochemical characteristic of bosentan (BOS) in comparison to tadalafil (TA) and sildenafil citrate (SIL). Despite some reports dealing with thermal characteristic of SIL and TA, physicochemical properties of BOS have not been investigated so far. Recent clinical reports have indicated that the combination of bosentan and PDE-5 inhibitor can improve the effectiveness of pharmacotherapy of pulmonary arterial hypertension (PAH). However, in order to design personalized medicines for therapy of chronic rare diseases, detailed information on the thermal behaviour and solubility of each drug is indispensable. Thus, XRD, DSC and TGA-QMS analyses were applied to compare the properties of the drugs, their thermal stability as well as to identify the products of thermal degradation. The dehydration of BOS started at 70°C and was followed by the chemical degradation with the onset at 290°C. The highest thermal stability was stated for TA, which decomposed at ca. 320°C, whereas the lowest onset of the thermal decomposition process was stated for SIL, i.e. 190°C. The products of the drug decomposition were identified. FT-FIR was applied to study intra- and intermolecular interactions between the drug molecules. FT-MIR and Raman spectroscopy were used to examine the chemical structure of the drugs. Chemoinformatic tools were used to predict the polar surface area, pKa, or logP of the drugs. Their results were in line with solubility and dissolution studies. [ABSTRACT FROM AUTHOR]

Background: There are currently three Food and Drug Administration approved endothelin receptor antagonists (ERAs): bosentan, ambrisentan, and macitentan. There is a growing body of evidence that demonstrates the beneficial effects of ERAs in patients with pulmonary arterial hypertension (PAH). Objectives: To compare the available evidence from randomized clinical trials for specific outcomes of different endothelin antagonists for the treatment of PAH. Methods: A multi-database search of randomized controlled trials up to March 15, 2016 was conducted for those that would measure functional parameters of patients with PAH treated with ERA monotherapy versus placebo. Studies that analyzed 6-min walking distance, pulmonary vascular resistance, pulmonary arterial pressure, or WHO functional status were incorporated for analysis. A total of 15 trials and 2 subanalyses were compiled and quality and abovementioned outcomes were compared among studies. Results: A constant decrease in pulmonary vascular resistance and pulmonary arterial pressure was globally reported among the different studies, resulting in increased 6-min walking distance and functional status compared to placebo. Conclusions: Although this evidence clearly shows the benefit of ERAs, studies, which compare ERAs against one another and with other therapies for progressive PAH, have been lacking. Larger and longer studies are necessary to define the role of ERAs as standalone agents and in combination therapies. [ABSTRACT FROM AUTHOR]

Bosentan monohydrate (4- tert-butyl- N-[6-(2-hydroxyethoxy)-5-(2-methoxyphenoxy)-2-(pyrimidin-2-yl) pyrimidin-4-yl]benzene-1-sulfonamide monohydrate) is a dual endothelin receptor antagonist (ERA) applied in the treatment of pulmonary arterial hypertension. To achieve effective process control of the bosentan monohydrate synthesis, it was necessary to develop a selective and not highly time-consuming method for ultra-high performance liquid chromatography (UHPLC). The method is characterized by adequate sensitivity, reproducibility and selectivity for the determination of bosentan monohydrate and related compounds from all synthetic stages. The UHPLC separation was carried out by reversed phase chromatography on the Acquity BEH C18 column (100 mm × 2.1 mm, 1.7 µm) with a mobile phase composed of solvent A (0.1 %, v/v, acetic acid in water) and solvent B (methanol), in the gradient mode at the flow rate of 0.4 mL min. Limits of detection and quantification for the compounds were ≤0.1 µg mL and 0.3 µg mL, respectively. The linearity for all related compounds was investigated as in the range for the active pharmaceutical ingredient (API) and as in the range for the in-process control. The developed method was validated according to the current guidelines, proving the suitability of the method for its intended purpose. [ABSTRACT FROM AUTHOR]

Fontan surgery is a widely used palliative procedure that significantly improves the survival period of patients with complex congenital heart disease (CHD). However, it does not decrease postoperative complication rate. Previous studies suggested that elevated mean pulmonary artery pressure (mPAP) and vascular resistance lead to decreased exercise tolerance and myocardial dysfunction. Therapy with endothelial receptor antagonists (Bosentan) has been demonstrated to improve the patients' prognosis. A double-blind, randomized controlled trial was performed to explore the efficacy of Bosentan in treating patients who underwent the Fontan procedure. Eligible participants were randomly divided into Bosentan group and control group. Liver function was tested at a local hospital and the results were reported to the phone inspector every month. If the results suggested abnormal liver function, treatment would be adjusted or terminated. All the participants finished the follow-up study, with no patients lost to follow-up. Unblinding after 2-year follow-up, no mortality was observed in either group. However, secondary end-points were found to be significantly different in the comparable groups. The cardiac function and 6-min walking distance in the Bosentan group were significantly superior to those in the control group ( P=0.018 and P=0.027). Bosentan could improve New York Heart Association (NYHA) functional status and improve the results of the 6-min walking test (6MWT) in Fontan patients post-surgery, and no other benefits were observed. Furthermore, a primary meta-analysis study systematically reviewed all the similar clinical trails worldwide and concluded an overall NYHA class improvement in Fontan patients who received Bosentan treatments. [ABSTRACT FROM AUTHOR]

This review will discuss the medical management of pulmonary hypertension in patients with left ventricular assist devices. Although much has been written on the management of primary pulmonary hypertension, also called pulmonary arterial hypertension, this review will instead focus on the treatment of pulmonary hypertension secondary to left heart disease. The relevant pharmacotherapy can be divided into medications for treating heart failure, such as diuretics and β-blockers, and medications for treating pulmonary hypertension. We also discuss important preoperative considerations in patients with pulmonary hypertension; the relationships between left ventricular assist devices, pulmonary hemodynamics, and right heart failure; as well as optimal perioperative and long-term postoperative medical management of pulmonary hypertension. [ABSTRACT FROM AUTHOR]

The aim of this study was to evaluate in systemic sclerosis (SSc) retrospectively the effect of Bosentan and Sildenafil and their combination on Raynaud's phenomenon (RP), function, and capillaroscopic patterns. One hundred and twenty-three SSc patients (mean age ± sd, 57.69 ± 14.07 years) were retrospectively evaluated and divided into two groups according to American College of Rheumatology (ACR)/European League Against Rheumatism (EULAR) classification score: group 1 score < 10, group 2 score > 10. Each group was divided into three subgroups according to treatment: Bosentan, Sildenafil, and Bosentan + Sildenafil. Nailfold videocapillaroscopy (NVC), Scleroderma Health Assessment Questionnaire (SHAQ) and Raynaud Condition Score (RCS) were performed at baseline and after 3 and 6 months. In Bosentan (29 patients: 12, group 1; 17, group 2), NVC changed significantly in both groups, after 3 and 6 months ( p = 0.00439, group 1; p = 0.00035, group 2). In group 1, the 'active' and the 'late' patterns reduced, and the 'aspecific' increased. In group 2, there was a reduction of late patterns, a worsening of SHAQ ( p < 0.005) and an improvement of RCS ( p = 0.00014). In Sildenafil (63 patients: 35, group 1; 28, group 2), after 3 months, NVC patterns changed significantly in both groups( p = 0.042 group 1, p = 0.00089 group 2). In group 1, the late and early patterns increased, and the aspecific decreased. In group 2, a significant change of NVC pattern was observed also after 6 months ( p = 0.00089): the late pattern increased while the active one reduced. After 6 months, SHAQ was significantly reduced in group 1 ( p = 0.00027) and in group 2 ( p = 0.0043). RCS improved in both groups ( p = 0.0042, group 1; p = 0.0016, group 2). Combination therapy (Bosentan + Sildenafil) (31 patients: 14, group 1; 17, group 2) induced significant changes on NVC only in group 1 after 3 ( p = 0.00256) and 6 months ( p = 0.000349) with a reduction of the late and active patterns and an increase of the early pattern. In both groups, after 6 months, SHAQ ( p < 0.05, group 1; p = 0.00049, group 2) and RCS significantly reduced (group 1, p = 0.00024; group 2, p = 0.0021). Patients treated with Bosentan + Sildenafil show a significant improvement of RCS and NVC. This combination therapy may exert a vascular activity achieving an amelioration of the structure of microvasculature in SSc. [ABSTRACT FROM AUTHOR]

Pulmonary arterial hypertension (PAH) trial has mostly enrolled patients with World Health Organization functional class (WHO FC) III or IV. However, PAH is rapidly progressive in nature even in patients with less severe forms at diagnosis. Following the recent studies in Western population, here we assessed the efficacy of bosentan in Japanese patients with WHO FCII PAH. In this open-label trial, bosentan 125 mg twice daily was administered for 12 weeks in 16 patients, and a hemodynamic evaluation was performed. Treatment was continued for a further 12 weeks, where the effect on exercise capacity was assessed in 13 patients. In 16 patients, mean pulmonary arterial pressure decreased from 40.4 ± 10.4 to 35.6 ± 12.6 mmHg ( p = 0.018) and cardiac index increased from 2.54 ± 0.73 to 2.96 ± 0.82 L/min/m ( p = 0.023). Thus, pulmonary vascular resistance decreased from 792 ± 565 to 598 ± 558 dyn·sec/cm ( p = 0.006). In 13 patients followed up for 24 weeks, 6-min walking distance increased from baseline at Week 12 ( p = 0.003) and Week 24 ( p = 0.011). All patients were mildly symptomatic at baseline with dyspnea index (Borg scale) of 2.50 ± 1.58 and the specific activity scale (SAS) of 5.0 ± 1.4 METs. These values remained unchanged throughout the study. These results suggest that bosentan treatment was beneficial for Japanese patients with WHO FC II PAH and treatment should be started in the early stage of the disease. [ABSTRACT FROM AUTHOR]

Bosentan is a mixed endothelin receptor antagonist widely used to treat patients with pulmonary arterial hypertension, and the emerging literature suggests bosentan as a potent anti-inflammatory drug. Superoxide anion is produced in large amounts during inflammation, stimulates cytokine production, and thus contributes to inflammation and pain. However, it remains to be determined whether endothelin contributes to the inflammatory response triggered by the superoxide anion. The present study investigated the effects of bosentan in a mouse model of inflammation and pain induced by potassium superoxide, a superoxide anion donor. Male Swiss mice were treated with bosentan (10-100 mg/kg) by oral gavage, 1 h before potassium superoxide injection, and the inflammatory response was evaluated locally and at spinal cord (L4-L6) levels. Bosentan (100 mg/kg) inhibited superoxide anion-induced mechanical and thermal hyperalgesia, overt pain-like behavior (abdominal writhings, paw flinching, and licking), paw edema, myeloperoxidase activity (neutrophil marker) in the paw skin, and leukocyte recruitment in the peritoneal cavity. Bosentan also inhibited superoxide anion-induced interleukin-1 beta (IL-1β) and tumor necrosis factor alpha (TNF-α) production, while it enhanced IL-10 production in the paw skin and spinal cord. Bosentan inhibited the reduction of antioxidant capacity (reduced glutathione, ferric reducing antioxidant power, and ABTS radical scavenging ability) induced by the superoxide anion. Finally, we demonstrated that intraplantar injection of potassium superoxide induces the mRNA expression of prepro-endothelin-1 in the paw skin and spinal cord. In conclusion, our results demonstrated that superoxide anion-induced inflammation, pain, cytokine production, and oxidative stress depend on endothelin; therefore, these responses are amenable to bosentan treatment. [ABSTRACT FROM AUTHOR]

The purpose of this study was to examine the effects bosentan (which is a strong vasoconstrictor) on bone fracture pathophysiology, and investigate the roles of the nonselective endothelin 1 receptor blocker bosentan on the bone fractures formed in rats through radiographic, histopathologic, and immunohistochemical methods. The rats were divided into three groups (six rats in each group): a femoral fracture control group, a femoral fracture plus bosentan at 50 mg/kg group, and a femoral fracture plus bosentan at 100 mg/kg group. The femoral fracture model was established by transversely cutting the femur at the midsection. After manual reduction, the fractured femur was fixed with intramedullary Kirschner wires. The radiographic healing scores of the bosentan 100 and 50 mg/kg groups were significantly better that those of the fracture control group. The fracture callus percent of new bone in the bosentan 100 mg/kg group was significantly greater than that in the control group. Also, semiquantitative analysis showed higher positive vascular endothelial growth factor and osteocalcin staining and lower positive endothelin receptor type A staining in the treatment groups than in the control group. Bosentan treatment also decreased tissue endothelin 1 expression relative to that in the fracture control group. As a result of our study, the protective effect of bosentan was shown in experimental femoral fracture healing in rats by radiographic, histopathologic, and molecular analyses. [ABSTRACT FROM AUTHOR]

Background: Lung hypoplasia, pulmonary persistent hypertension of the newborn and its morphological changes are the main features in congenital diaphragmatic hernia (CDH). This study was undertaken to investigate if antenatal use of sildenafil and/or bosentan attenuates vascular remodeling, promotes branching, and improves alveolarization in experimental nitrofeninduced CDH. Methods: Nitrofen (100 mg) was gavage-fed to pregnant rats at post conception day (PCD) 9 to induce CDH. The rats were randomized to 5 groups: 1) control; 2) nitrofen; 3) nitrofen+sildenafil 100 mg/kg per day at PCD 16-20; 4) nitrofen+bosentan 30 mg/kg per day, at PCD 16-20, and 5) nitrofen+bosentan+sildenafil, same doses and administration days. After cesarean delivery, the offsprings were sacrificed. The diaphragmatic defect and pulmonary hypoplasia were identified, and the lungs were dissected. Arterial wall thickness, bronchiolar density and alveolarization were assessed. Results: The offsprings with CDH were characterized by severe pulmonary hypoplasia (lung weight-to-body weight ratio: 0.0263 [95% confidence interval (CI) 0.0242-0.0278)] in the nitrofen group versus 0.0385 (95% CI 0.0355-0.0424) in the control group ( P=0.0001). Pulmonary arterial wall thickness was decreased to 3.0 (95% CI 2.8-3.7) μm in the nitrofen+sildenafil group versus 5.0 (95% CI 4.1-4.9) μm in the nitrofen group ( P=0.02). Terminal bronchioles increased to 13.7 (95% CI 10.7-15.2) μm in the nitrofen+bosentan group in contrast to 8.7 (95% CI 7.2-9.4) μm in the nitrofen group ( P=0.002). More significant differences ( P=0.0001) were seen in terminal bronchioles in the nitrofen+sildenafil+bosentan group than in the nitrofen group [14.0 (95% CI 12.5-15.4) μm versus 8.5 (95% CI 7.1-9.3) μm]. Pulmonary arterial wall thickness was also decreased in the former group. Conclusions: In this rat model, antenatal treatment with sildenafil attenuates vascular remodeling. Bosentan promotes the development of terminal bronchioles in nitrofen-induced CDH. [ABSTRACT FROM AUTHOR]

The aim of this study was to evaluate the effects of bosentan on plasma endothelin-1 (ET-1) and nitric oxide (NO) as pulmonary hypertension (PH)-associated biochemical markers in patients with systemic sclerosis (SSc). Twenty-four SSc patients receiving bosentan for 24 weeks were registered in this prospective observational study. Ten patients were complicated with clinically suspected PH. Plasma levels of ET-1 and NO were assessed at baseline and after 24 weeks of treatment in SSc patients and in 15 healthy controls. Plasma levels of ET-1 and NO at baseline were significantly higher in SSc patients than in healthy controls ( p < 0.000), and they were also significantly higher in SSc patients with PH than in those without PH ( p < 0.01). Plasma ET-1 levels were significantly decreased after 24 weeks of bosentan therapy ( p < 0.0001), and ET-1 levels of SSc patients with PH decreased to a level comparable to that in patients without PH. In the 10 SSc patients with PH, changes in plasma ET-1 levels during the 24 weeks of the study were significantly larger in the 5 patients whose functional class (FC) improved than in the 5 patients whose FC was unchanged ( p < 0.05). Plasma NO levels were also slightly decreased in SSc patients after 24 weeks of bosentan therapy. Plasma ET-1 levels could reflect the presence and severity of PH in SSc patients. Additionally, changes in plasma ET-1 levels may indicate the response to bosentan therapy in SSc patients with PH. [ABSTRACT FROM AUTHOR]

Purpose: Both sildenafil and bosentan have been used clinically to treat pulmonary arterial hypertension. As these substances target different pathways to modulate vasoconstriction, we investigated the combined effects of both drug classes in isolated human pulmonary vessels. Methods: Segments of pulmonary arteries (PA) and veins (PV) were harvested from 51 patients undergoing lobectomy. Contractile force was determined isometrically in an organ bath. Vessels were constricted with norepinephrine (NE) to determine effects of sildenafil. They were constricted with ET-1 to assess effects of bosentan, and with NE and ET-1 to evaluate the combination of both substances. Results: Sildenafil (1E-5 M) significantly reduced maximum constriction by NE of both PA (13.0 ± 11.1 vs. 34.9 ± 7.6 % relative to KCl induced constriction; n = 6; p < 0.001) and PV (81.2 ± 34.2 vs 121.6 ± 20.8 %; n = 6; p < 0.01) but did not affect basal tones. Bosentan (1E-5 M) significantly reduced maximum constriction of PV (56.6 ± 21.5 vs. 172.1 ± 30.0 %; n = 6; p < 0.01) by ET-1 and led to a small but insignificant decrease of basal tone ( p = 0.07). Bosentan almost completely abolished constriction of PA (1.0 ± 0.9 vs. 74.7 ± 25.7 %; n = 6; p < 0.001) by ET-1, but did not affect basal tone. Bosentan (1E-7 M) significantly attenuated combined ET-1/NE dose-response curves in PA (93.1 ± 47.4 vs. 125.3 ± 41.0 %; n = 12; p < 0.001) whereas the effect of sildenafil (1E-5 M) was less pronounced (103.6 ± 20.2 %; p < 0.05). Simultaneous administration of both substances showed a significantly greater reduction of maximum constriction in PA compared to individual administration (64.6 ± 26.3 %; p < 0.001). Conclusions: Sildenafil only at its highest concentration was effective in suppressing NE induced pulmonary vessel contraction. Bosentan was able to completely suppress ET-1 induced contraction of PA and strongly attenuated contraction of PV. The present data suggest a benefit of sildenafil/bosentan combination therapy as they affect different pathways and may allow lower dosages. [ABSTRACT FROM AUTHOR]

Digital ulcers (DU) are one of the most common and debilitating manifestations of vasculopathy in systemic sclerosis (SSc). Their prevention is important in order to improve patients' outcome and as a result of the economic impact they have on society. Randomised controlled studies have demonstrated that bosentan, an endothelin receptor antagonist, reduces the appearance of new DU. The aim of this retrospective study was to evaluate the occurrence of DU in a group of patients receiving long-term bosentan treatment for pulmonary arterial hypertension associated with SSc (PAH-SSc). Patients with PAH-SSc and treated with bosentan for at least 6 months ( n = 30) were evaluated. Thirty patients with SSc not treated with bosentan, but matched for sex, age, disease duration and cutaneous form of SSc, were considered as a control group. The occurrence of DU, defined as loss of tissue of varying degrees in the epidermis, dermis and subcutaneous tissue, was determined in the bosentan-treated and untreated groups. Mean duration of bosentan treatment was 3.6 years. DU were detected in six patients in the bosentan-treated group (20.0 %) and 16 patients (53.3 %) in the untreated group ( p = 0.0015). There were no significant differences in demographic or clinical characteristics between patients with or without DU at study end. The occurrence of DU in patients with PAH-SSc receiving long-term bosentan treatment was significantly lower than in untreated patients. The results from this long-term observational study provide valuable information on management of patients with PAH-SSc. [ABSTRACT FROM AUTHOR]

Objective: Endothelins (ETs) are involved in several inflammatory events. The present study investigated the efficacy of bosentan, a dual ETA/ETB receptor antagonist, in collagen-induced arthritis (CIA) in mice. Treatment: CIA was induced in DBA/1J mice. Arthritic mice were treated with bosentan (100 mg/kg) once a day, starting from the day when arthritis was clinically detectable. Methods: CIA progression was assessed by measurements of visual clinical score, paw swelling and hypernociception. Histological changes, neutrophil infiltration and pro-inflammatory cytokines were evaluated in the joints. Gene expression in the lymph nodes of arthritic mice was evaluated by microarray technology. PreproET-1 mRNA expression in the lymph nodes of mice and in peripheral blood mononuclear cells (PBMCs) was evaluated by real-time PCR. The differences were evaluated by one-way ANOVA or Student's t test. Results: Oral treatment with bosentan markedly ameliorated the clinical aspects of CIA (visual clinical score, paw swelling and hyperalgesia). Bosentan treatment also reduced joint damage, leukocyte infiltration and pro-inflammatory cytokine levels (IL-1β, TNFα and IL-17) in the joint tissues. Changes in gene expression in the lymph nodes of arthritic mice returned to the levels of the control mice after bosentan treatment. PreproET mRNA expression increased in PBMCs from rheumatoid arthritis (RA) patients but returned to basal level in PBMCs from patients under anti-TNF therapy. In-vitro treatment of PBMCs with TNFα upregulated ET system genes. Conclusion: These findings indicate that ET receptor antagonists, such as bosentan, might be useful in controlling RA. Moreover, it seems that ET mediation of arthritis is triggered by TNFα. [ABSTRACT FROM AUTHOR]

Aims/hypothesis: Endothelial dysfunction is important in the development of vascular complications in diabetes. Patients with type 2 diabetes have increased production of the vasoconstrictor and pro-inflammatory peptide, endothelin-1. Short-term intra-arterial administration of endothelin antagonists improves endothelium-dependent vasodilatation in patients with type 2 diabetes. We tested the hypothesis that oral administration of the dual endothelin receptor antagonist, bosentan, improves peripheral endothelial function in patients with type 2 diabetes and microalbuminuria. Methods: This placebo-controlled and double-blind study was performed on 46 patients with type 2 diabetes and microalbuminuria (urine albumin/creatinine ratio >3 mg/mmol) at a medical university department. Patients were randomised to bosentan, 125 mg two times per day ( n = 28), or placebo ( n = 28) for 4 weeks. The computer-generated randomisation code was kept in sealed envelopes. Patients and people doing examinations or assessing outcomes were blinded. The primary endpoint was change in microvascular endothelium-dependent vasodilatation, based on change in digital reactive hyperaemia index. The secondary endpoint was change in brachial artery flow-mediated vasodilatation. Results: Reactive hyperaemia index increased from 1.73 ± 0.43 (mean ± SD) at baseline to 2.08 ± 0.59 at follow-up ( p < 0.05) in the bosentan group ( n = 22), but did not change in the placebo group (1.84 ± 0.49 to 1.87 ± 0.47; n = 24). The change in reactive hyperaemia index from baseline was greater in the bosentan group than in the placebo group ( p < 0.05). Nitroglycerine-induced digital hyperaemia was not affected. Brachial artery flow-mediated vasodilatation and blood pressure did not change during treatment. Conclusions/interpretation: Oral treatment of 4 weeks duration with the dual endothelin receptor antagonist, bosentan, improves peripheral endothelial function in patients with type 2 diabetes and microalbuminuria. Trial Registration:: ClinicalTrial.gov NCT01357109; Karolinska Clinical Trial Registration Identifier CT20090017 (see ) Funding:: Research Council of Sweden, Swedish Heart and Lung Foundation, Novo Nordisk Foundation, Karolinska Institutet/Stockholm County Council Strategic Cardiovascular Programme, Gustav V and Queen Victoria Foundation, the Family Erling Persson Foundation, Actelion Pharmaceuticals and Actelion Research Award. [ABSTRACT FROM AUTHOR]

Advances in antiretroviral therapy have turned HIV into a chronic, manageable disease. Patients often require treatment for co-morbid conditions as well as HIV, and consequently, pharmacokinetic interactions between antiretrovirals (ARVs) and other drug classes are an increasing concern. Protease inhibitors and non-nucleoside reverse transcriptase inhibitors are involved in the CYP450 or other transporter systems, and may be associated with higher risk of clinically significant drug interactions. One reverse transcriptase inhibitor, abacavir, has demonstrated weak inhibition of CYP3A4, 2D6 and 2C9 in vitro, but is not associated with any clinically significant interactions involving the CYP450 system. The integrase inhibitor raltegravir is not involved in the CYP450 system, and may be a suitable option to use when trying to minimize interactions with other drug classes. This review summarizes recently published data on clinically significant drug interactions between ARVs and other drug classes including antineoplastics, immunosuppressant transplant drugs, directly acting antivirals for hepatitis C, antifungals, antimalarials, corticosteroids, psychotropics, hormonal contraceptives, anticoagulants, drugs for pulmonary hypertension, and herbal products. In situations of suspected or potential interactions, close monitoring is warranted, and dose adjustments or substitutions may be required. [ABSTRACT FROM AUTHOR]

The present study was designed to examine the potential preventive and curative effects of curcumin, resveratrol, imatinib, rosiglitazone, losartan and bosentan (BOS) on Schistosoma mansoni-induced liver fibrosis in mice. Induction of liver fibrosis was produced in male Swiss mice by subcutaneous injection of S. mansoni cercariae per mouse. Mice were left for 28 days before starting the experiment then mice were divided into two main groups. The first group was further subdivided into experimental groups and started drug treatment at day 28 after infection and continued for 2 weeks in order to evaluate the potential preventive effects of the mentioned drugs on S. mansoni-induced liver fibrosis. The second group of mice were left for 2 weeks and then treated with praziquantel for two consecutive days to eradicate the worms and so stop egg disposition and further fibrosis development. Mice were then subdivided into the experimental groups and drug treatment was started for 2 weeks to evaluate their efficacy to decrease the developed fibrosis. At the end of the experiment period, mice were killed and serum was collected for the estimation of alanine aminotransferase (ALT), aspartate aminotransferase (AST), bilirubin and albumin. Liver tissue was taken for the estimation of hepatic hydroxyproline content and histopathological examination to confirm the biochemical results. Results of the study indicate that curcumin and imatinib have potent antifibrotic activity both in suppressing and reversing S. mansoni-induced liver fibrosis, while resveratrol has beneficial effects only in suppressing the development of S. mansoni-induced liver fibrosis. [ABSTRACT FROM AUTHOR]

Pulmonary hypertension in heart failure is associated with exercise intolerance and adverse outcomes. With the availability of multiple drugs that cause pulmonary vasodilation and decrease pulmonary arterial pressure, pulmonary hypertension becomes an attractive therapeutic target. Out of several classes of medications, oral phosphodiesterase inhibitors emerge as the most promising in terms of symptomatic improvement, hemodynamic benefits, reverse cardiac remodeling, and functional capacity. Future trials will show whether the use of these drugs translates to decreased morbidity and mortality in heart failure. [ABSTRACT FROM AUTHOR]

This study aimed to investigate the efficacy of bosentan in the treatment of severe pulmonary hypertension in a young female patient with mixed connective tissue disease (MCTD) associated with antiphospholipid syndrome. A 27-year-old woman presented with sudden onset of dyspnea. She had not experienced any dyspnea before this period, and she was known to have MCTD. Laboratory tests showed positive results for antinuclear antibodies, anti-RNP antibodies, anticardiolipin antibodies, β-glycoprotein I, and lupus anticoagulant. A complete echocardiographic study was performed demonstrating a pulmonary artery systolic pressure (PAPs) of 85 mmHg. Treatment with bosentan was initiated. After 12 days, the patient improved clinically. After 6 months of therapy, the follow-up echocardiography showed a near-normalization of PAPs. Patients who develop PAH secondary to an underlying systemic disease often have a poor survival rate. In this report, we describe a correlation between anticardiolipin antibodies and rapidly progressive pulmonary hypertension. Indeed, the patient in this study very likely improved secondary to the effect of bosentan which produces systemic and pulmonary vasodilatation associated with pulmonary vascular remodeling as well as possible antifibrotic, anti-inflammatory and antiatherothrombotic effects on cells of lungs damaged by an aPL-antibody mediated mechanism. [ABSTRACT FROM AUTHOR]

The endothelium-derived vasoconstrictor molecule endothelin-1 (ET-1) has been suggested to play a role in the pathogenesis of Raynaud’s phenomenon (RP) and systemic sclerosis (SSc). We studied the effect of bosentan on microvascular structure and function in patients with RP secondary to limited cutaneous SSc in a mechanistic pilot study. In this single center, open study, 15 patients with limited cutaneous SSc were treated with bosentan for 16 weeks with a follow-up period of 4 weeks. Changes in microvascular structure and function were studied with assessment of vasodilatory microvascular responses using laser Doppler fluxmetry combined with iontophoresis, capillary permeability using fluorescence videomicroscopy, nailfold capillary microscopy, and serological markers of endothelial activation. No significant changes were seen in vasodilator responses to acetylcholine and sodium nitroprusside following bosentan treatment. No effect was noted on capillary permeability during treatment. The number of nailfold capillaries remained unchanged. The endothelial activation marker vascular cell adhesion molecule did not change during treatment, but levels of thrombomodulin significantly decreased after 12 weeks of treatment. Bosentan did not induce significant changes in vasodilator responses, capillary permeability, and capillary density during treatment, so no evidence was obtained for structural improvement of microvascular structure and function in this short-time mechanistic pilot study in patients with lcSSc. [ABSTRACT FROM AUTHOR]

Introduction: Pulmonary arterial hypertension is a rare disorder in childhood, the two most common types being idiopathic pulmonary arterial hypertension and pulmonary hypertension associated with congenital left-to-right shunt lesions, together accounting for almost 90% of cases.Discussion: The clinical presentation of idiopathic pulmonary arterial hypertension (familial and non familial) is essentially non-specific and varies with age. Pulmonary vasoreactivity testing identifies responders and non-responders. Responders are treated with calcium channel blockers and have a better prognosis. Non-responders have a very limited survival beyond diagnosis if not treated with more selective pulmonary arterial vasodilators. Prostacyclin, endothelin receptor antagonists and phosphodiesterase-5 inhibitors improve haemodynamics, functional class and exercise tolerance and delay deterioration. Patients with congenital left-to-right shunts and irreversible pulmonary arterial hypertension leading to Eisenmenger's syndrome have multiple organ disease. Despite a very pronounced exercise intolerance, their clinical course is rather stable with survival up to 40-60 years, depending on the complexity of their underlying cardiac defect. Treatment is based on general measures along with the same three types of selective pulmonary vasodilators as in idiopathic pulmonary arterial disease. Improvement in haemodynamics, functional class and exercise tolerance are comparable for both patient groups.Conclusion: Pulmonary hypertension in children is idiopathic or associated with congenital heart disease in the majority of patients. Treatment with new selective pulmonary vasodilators offers haemodynamic and functional improvement. [ABSTRACT FROM AUTHOR]

Effects of a dual endothelin receptor antagonist, bosentan on peripheral circulatioin and skin lesions as well as pulmonary arterial hypertension (PAH) were investigated in Japanese patients with connective tissue diseases (CTD). Fifteen patients with PAH associated with CTD [systemic sclerosis (SSc) 13, mixed connective tissue disease (MCTD) 2] were treated with bosentan for 40–96 weeks, and changes of exercise capacity (6-min walk distance and Borg’s dyspnea scale), cardio-pulmonary hemodynamics (right ventricular pressure, specific activity scale and cardiac index), Raynaud’s phenomenon, digital ulcers and dermal sclerosis were observed. Bosentan improved exercise capacity, had a positive effect on hemodynamic parameters, and was well tolerated as previously reported. After a median 8 weeks of treatment, 13 out of 15 patients had improved Raynaud’s phenomenon. Digital ulcers also improved after a median 12 weeks’ treatment in all of 8 patients. Modified Rodnan total skin score decreased from 21.0 ± 5.9 to 11.5 ± 3.9 in diffuse cutaneous SSc and from 17.0 ± 6.5 to 9.5 ± 4.5 in limited cutaneous SSc after 24 months’ treatment, reaching significance after 6 months in both groups. These data suggest that bosentan is effective for both PAH and peripheral vascular diseases in Japanese patients with CTD. The pathological background to the improvement in dermal sclerosis observed in this study should be further investigated. [ABSTRACT FROM AUTHOR]

Chronic lung disease (CLD) is often complicated by chronic pulmonary vascular changes and pulmonary hypertension (PH) in young children. Current therapies for severe PH in such patients, including oxygen, inhaled nitric oxide, and parenteral prostacyclin, are often suboptimal, cumbersome, and expensive. Recently, oral endothelin receptor blockers and phosphodiesterase-5 inhibitors have been used successfully to control and reverse pulmonary vascular disease in idiopathic PH, but the use and efficacy of these agents in pediatric CLD have not been previously reported. We report a series of six children with CLD and severe PH treated with bosentan (six of six) and sildenafil (four of six). Vascular reactivity was assessed by cardiac catheterization prior to and after 6 months of therapy. Serial echocardiography was also used to assess response. Patients have been treated for 2.1–2.9 years (mean, 2.53 years). Response to therapy has included improvement in oxygenation, symptoms, echocardiographic parameters, and hemodynamics by cardiac catheterization. Transiently elevated liver enzymes were noted associated with viral respiratory infections in two subjects; no other adverse effects were noted. Three patients with large cardiac right-to-left shunts prior to therapy had subsequent shunt reversal, two of whom underwent shunt closure later. Oral therapy with bosentan alone or in combination with sildenafil improves PH in patients with CLD over a period of 3–4 years. [ABSTRACT FROM AUTHOR]

The purpose of our study was to investigate the effect of bosentan treatment on surrogate markers in patients with systemic-sclerosis-related pulmonary arterial hypertension (SScPAH). We studied ten SScPAH patients (nine female, median age 58 years, median duration of disease 9 years). Six-minute walk test (SMWT) and plasma N-terminal probrain natriuretic peptide (NT-proBNP) levels were recorded from patients at baseline and after 20 weeks under bosentan treatment. Wilcoxon paired signed rank test was applied in order to compare NT-proBNP levels and SMWT at baseline and week 20. At week 20, NT-proBNP levels were decreased from a median of 474 fmol/ml (range, 212–1407 fmol/ml) at baseline to 238 fmol/ml (range, 198–335 fmol/ml; p = 0.002). Mean SMWT distance increased from a baseline median value of 323 m (range, 224–368 m) to 372 m (range, 232–530 m), representing a nonsignificant increase. Our results suggest that NT-proBNP is a biochemical surrogate marker, which could be used to evaluate the effects of bosentan or other vasodilation therapy in SScPAH. [ABSTRACT FROM AUTHOR]

Systemic sclerosis (SSc) is characterized by vascular dysfunction that may lead to pulmonary artery hypertension (PAH). The N-terminal pro-B type natriuretic peptide (NT-proNBP), a marker of cardiac failure, is a diagnostic marker of early PAH in patients with SSc without heart failure. Our aim was to determine whether NT-proBNP levels may be a useful tool to evaluate the response to bosentan therapy in patients with PAH secondary to SSc. Ten patients with symptomatic, severe PAH secondary to SSc, received bosentan, 62.5 mg twice a day for 4 weeks followed by 125 mg twice a day for 7 months. Ten patients with SSc without PAH served as controls for basal level of NT-proBNP. Blood samples were obtained before the beginning of the therapy and after 3 and 7 months of treatment. SSc patients with PAH had significantly higher serum levels of NT-proBNP than those without PAH, at baseline. After 3 and 7 months of therapy, NT-proBNP concentration showed a progressive decrease, nearly approaching statistical difference at 7 months when compared to baseline levels ( P = 0.953 and P = 0.600). Our results show that serum NT-proBNP levels may be a useful marker for the response to bosentan therapy in patients with PAH secondary to SSc. [ABSTRACT FROM AUTHOR]

Persistent pulmonary hypertension of the newborn (PPHN) occurs in 1-4% of neonates with transposition of the great arteries with intact ventricular septum (TGA/IVS). This association is often lethal. To our knowledge, only eight survivors have been described in the literature, two of whom benefited from extracorporeal membrane oxygenation (ECMO). We report two cases of PPHN complicating a TGA/IVS that were refractory to multiple therapies and resolved 48 hours after initiation of bosentan therapy. Bosentan, an oral dual endothelin-1 receptor antagonist, is a new treatment for pulmonary arterial hypertension that was both effective and safe in these two cases of TGA/IVS with PPHN. To our knowledge, it is the first use of bosentan in newborns. [ABSTRACT FROM AUTHOR]

The aim of this study was to systematically investigate the mutual pharmacokinetic interactions in healthy volunteers between sildenafil, a phosphodiesterase-5 inhibitor, and bosentan, a dual endothelin receptor antagonist, both approved for treating pulmonary arterial hypertension (PAH). A randomised, double-blind, placebo-controlled, parallel-group study with three treatment arms (sildenafil plus placebo, bosentan plus placebo and sildenafil plus bosentan) was conducted in 55 healthy male volunteers (51 completers). Study duration was 18 days per treatment group. Sildenafil was administered three times daily on Days 1–6 and 11–16 (20 mg initially, increased to 80 mg after 3 days), and bosentan (125 mg) was administered twice daily on Days 7–17. On Day 16, bosentan decreased the maximum plasma concentration of sildenafil ©max) by 55.4% [90% confidence interval (CI) 40.3–66.6%] and the area under the plasma concentration versus time curve over a dosing interval $$ {\left( {{\text{AUC}}_{\tau } } \right)} $$ by 62.6% (90% CI 56.8–67.7%). Sildenafil increased bosentan Cmax by 42.0% (90% CI 15.4–74.8%) and $$ {\left( {{\text{AUC}}_{\tau } } \right)} $$ by 49.8% (90% CI 28.7–74.5%). Bosentan and sildenafil in combination were well tolerated, with no serious adverse events reported. All adverse events were of mild or moderate intensity. In healthy volunteers, there is a mutual pharmacokinetic interaction between bosentan and sildenafil that may influence the dosage of each drug in a combination treatment. The clinical implications of combination therapy with bosentan and sildenafil are as yet unknown, and further trials in patients with PAH are needed. [ABSTRACT FROM AUTHOR]

There is no effective systemic therapy for disseminated metastatic melanoma. Data suggest that endothelin may play a role in pathophysiology of melanoma and that the dual endothelin receptor antagonist bosentan may have anti-tumor activity. This multicenter, open-label, single-arm, prospective, proof-of-concept study assessed the effects of bosentan monotherapy (500 mg oral tablets, bid) on tumor response in patients with stage IV metastatic melanoma. Patients were treated until disease progression, death or serious adverse event leading to premature study drug discontinuation. Tumor response was assessed at 6-weekly intervals using the Response Evaluation Criteria in Solid Tumors (RECIST). Among the 35 patients included in this study with stage IV metastatic melanoma, 21 (60%) were stage M1C, 10 (29%) stage M1B and 4 (11%) stage M1A (American Joint Committee on Cancer [AJCC] classification). Nine patients (26%) had received prior therapy for stage IV melanoma. Disease stabilization was observed in 6 of the 32 patients analyzed per protocol at week 6 with confirmatory evaluation at week 12, 5 of whom were still stable at ≥24 weeks. Of the 6 patients with disease stabilization, 2 were stage M1A, 1 was stage M1B and the remaining 3 were stage M1C. Partial or complete response was not observed. Progressive disease was observed in 17 (49%) patients at week 12 and in 25 (71%) patients at the end of the study (data base closure). The most frequent adverse events were typical for the underlying disease or known to be associated with bosentan: headache (43%), fatigue (34%), nausea (31%), back pain (23%) and abnormal hepatic function (23%). Bosentan might have benefit in disease stabilization in certain patients with metastatic melanoma and deserves further investigation in combination with other anticancer drugs. [ABSTRACT FROM AUTHOR]

Diabetes mellitus is complicated with the development of cardiac contractile dysfunction and electrical instability, which contributes to high morbidity and mortality in diabetic patients. This study examined the possible roles of enhanced endothelin-1 (ET-1) on diabetes-induced alterations in ventricular myocyte electrophysiology. Type 1 diabetic rats were induced by single dose injection of streptozotocin (STZ) and treated with or without ET-1 receptor antagonist bosentan for 8 wk before myocyte isolation. Action potential, outward K currents, and inward Ca currents in ventricular myocytes were recorded using whole-cell patch clamp technique. STZ-injected rats exhibited hyperglycemia, reduced body weight gain, and elevated plasma ET-1 concentration, indicative of diabetes induction. Ventricular myocytes isolated from diabetic rats exhibited prolonged action potential and reduced all three types of outward K currents. Resting membrane potential, height of action potential, and L-type Ca current were not altered in diabetic myocytes. In vivo chronic treatment of diabetic rats with bosentan significantly augmented K currents and reversed action potential prolongation in ventricular myocytes. On the other hand, bosentan treatment had no detectable effect on the electrophysiological properties in control myocytes. In addition, bosentan had no effect on L-type Ca currents in both control and diabetic myocytes. Our data suggest that altered electrophysiological properties in ventricular myocytes were largely resulted from augmented ET-1 system in diabetic animals. [ABSTRACT FROM AUTHOR]

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In view of the shortcomings of the current system for postmarketing drug surveillance that is based on voluntary spontaneous adverse drug reaction (ADR) reporting, new approaches are needed. We describe an approach involving a combination of limited distribution, patient and physician education, as well as a novel pharmacovigilance system that is capable of promoting the safe and adequate use of a new drug. Importantly, it provides the possibility of calculating true ADR occurrence rates, as the exposed population (denominator) and the number of patients with events (numerator) are known. These measures were taken for the oral dual endothelin ETA/ETB antagonist bosentan (Tracleer®). In recent guidelines issued by the European Society of Cardiology, American College of Chest Physicians and the WHO, this drug is considered as first-line oral treatment for the treatment of pulmonary arterial hypertension, a devastating orphan disease associated with a poor prognosis. Bosentan was approved in 2001/2 on the basis of two pivotal studies that showed improved exercise capacity and haemodynamic parameters while delaying time to clinical worsening. Elevations in serum liver aminotransferase levels of >3 times the upper limit of normal were noted in 10.2% of patients (placebo-subtracted incidence). Therefore, liver function tests have to be performed on a regular basis. In addition, bosentan has potential as a teratogen. In the US, a controlled distribution network for bosentan (Tracleer® Access Program [T.A.P.]) and the development of a patient database to follow patients was set up. Accompanied by comprehensive physician and patient education programmes, T.A.P. was developed to provide a mechanism to assist with the primary risk management goals for bosentan therapy, namely pregnancy prevention and liver enzyme monitoring and prevention of hepatic injury. In Europe, the Tracleer® Excellence (TRAX PMS) database is a novel European non-interventional, prospective, internet-based surveillance system initiated by the manufacturer in cooperation with the European Medicines Agency. It collected potential safety signals associated with bosentan use including adverse events, elevations of liver aminotransferase levels, other abnormal laboratory values, death and hospitalisation. TRAX PMS has accrued 79% of all known patients in the EU and the data provide supportive ‘real-life’ evidence on the long-term safety of bosentan. The two different systems had similar goals and outcomes. The data received concerning thousands of patient-years of use have confirmed the clinical trial results regarding product safety and the favourable benefit/risk ratio of bosentan, especially with regard to known type A adverse events. The clinical monitoring algorithm has also been confirmed. In addition, no rare type B events were uncovered despite the increased reporting rate. These systems might serve as templates for future pharmacovigilance efforts regarding drugs that require particular safety attention. [ABSTRACT FROM AUTHOR]

During the last decade we have witnessed substantial improvements in the therapeutic options for pulmonary arterial hypertension (PAH), including true innovations targeting some of the mechanisms involved in the pathogenesis of this devastating disease. Intravenous epoprostenol was the first drug to improve symptoms and survival of patients with PAH. Novel prostanoids, including subcutaneous treprostinil and inhaled iloprost, also have beneficial effects in many patients, although their long-term efficacy is less well known. Among the newer treatments for PAH, endothelin receptor antagonists and phosphodiesterase type 5 (PDE5) inhibitors have reshaped clinical practice. The endothelin receptor antagonist bosentan has been approved in many parts of the world and most current guidelines recommend this drug as first-line treatment for patients with PAH in functional class III. Novel endothelin receptor antagonists such as sitaxsentan sodium and ambrisentan are currently being investigated. The PDE5 sildenafil is also being intensively studied in patients with pulmonary hypertension, and most of the available data look promising, although approval for PAH is still pending. Other PDE5 inhibitors have not yet undergone extensive study in PAH. The increasing insight into the pathogenesis of PAH opens several new therapeutic opportunities, which include vasoactive intestinal peptide, selective serotonin reuptake inhibitors, adrenomedullin and HMG-CoA reductase inhibitors (statins). However, PAH is a complex disorder and targeting a single pathway can not be expected to be uniformly successful. Thus, combining substances with different modes of action is expected to improve symptoms, haemodynamics and survival in PAH patients, although combination therapy has yet to undergo the scrutiny of large randomised clinical trials. [ABSTRACT FROM AUTHOR]

Bosentan, a dual endothelin receptor antagonist, is indicated for the treatment of patients with pulmonary arterial hypertension (PAH). Following oral administration, bosentan attains peak plasma concentrations after approximately 3 hours. The absolute bioavailability is about 50%. Food does not exert a clinically relevant effect on absorption at the recommended dose of 125mg. Bosentan is approximately 98% bound to albumin and, during multiple-dose administration, has a volume of distribution of 30L and a clearance of 17 L/h. The terminal half-life after oral administration is 5.4 hours and is unchanged at steady state. Steady-state concentrations are achieved within 3–5 days after multiple-dose administration, when plasma concentrations are decreased by about 50% because of a 2-fold increase in clearance, probably due to induction of metabolising enzymes. Bosentan is mainly eliminated from the body by hepatic metabolism and subsequent biliary excretion of the metabolites. Three metabolites have been identified, formed by cytochrome P450 (CYP) 2C9 and 3A4. The metabolite Ro 48-5033 may contribute 20% to the total response following administration of bosentan. The pharmacokinetics of bosentan are dose-proportional up to 600mg (single dose) and 500 mg/day (multiple doses). The pharmacokinetics of bosentan in paediatric PAH patients are comparable to those in healthy subjects, whereas adult PAH patients show a 2-fold increased exposure. Severe renal impairment (creatinine clearance 15–30 mL/min) and mild hepatic impairment (Child-Pugh class A) do not have a clinically relevant influence on the pharmacokinetics of bosentan. No dosage adjustment in adults is required based on sex, age, ethnic origin and bodyweight. Bosentan should generally be avoided in patients with moderate or severe hepatic impairment and/or elevated liver aminotransferases. Ketoconazole approximately doubles the exposure to bosentan because of inhibition of CYP3A4. Bosentan decreases exposure to ciclosporin, glibenclamide, simvastatin (and β-hydroxyacid simvastatin) and (R)- and (S)-warfarin by up to 50% because of induction of CYP3A4 and/or CYP2C9. Coadministration of ciclosporin and bosentan markedly increases initial bosentan trough concentrations. Concomitant treatment with glibenclamide and bosentan leads to an increase in the incidence of aminotransferase elevations. Therefore, combined use with ciclosporin and glibenclamide is contraindicated and not recommended, respectively. The possibility of reduced efficacy of CYP2C9 and 3A4 substrates should be considered when coadministered with bosentan. No clinically relevant interaction was detected with the P-glycoprotein substrate digoxin. In healthy subjects, bosentan doses >300mg increase plasma levels of endothelin-1. The drug moderately reduces blood pressure, and its main adverse effects are headache, flushing, increased liver aminotransferases, leg oedema and anaemia. In a pharmacokinetic-pharmacodynamic study in PAH patients, the haemodynamic effects lagged the plasma concentrations of bosentan. [ABSTRACT FROM AUTHOR]

Portopulmonary hypertension (PPHTN) is a rare complication of liver cirrhosis. Prostanoids have been shown to be effective in the treatment of PPHTN and have been used as a bridge to orthotopic liver transplantation. However, inhibition of platelet aggregation might be a limitation of prostacyclin therapy in patients with end-stage liver disease having an increased risk of bleeding from esophageal varices. The effect of oral bosentan, a dual endothelin-receptor antagonist in the reversal of PPHTN, is still unclear. We report a case of PPHTN (mean pulmonary artery pressure [mPAP] of 51 mmHg) that was successfully switched from inhalative iloprost to oral bosentan therapy. Hemodynamic and symptomatic improvements were maintained after a 12-month long-term treatment with inhalative iloprost as well as after single oral bosentan therapy. This is the first reported case of a successful switch from therapy with an inhalative prostacyclin analogue to oral bosentan in a patient suffering from PPHTN. Thus, oral bosentan therapy might be a promising new option for patients suffering from PPHTN. [ABSTRACT FROM AUTHOR]

Drugs that bind with high affinity and to a significant extent (relative to dose) to a pharmacologic target such as an enzyme, receptor, or transporter may exhibit nonlinear pharmacokinetic (PK) behavior. Processes such as receptor-mediated endocytosis may result in drug elimination. A general PK model for characterizing such behavior is described and explored through computer simulations and applications to several therapeutic agents. Simulations show that model predicted plasma concentration vs. time profiles are expected to be polyexponential with steeper distribution phases for lower doses and similar terminal disposition phases. Noncompartmental parameters always show apparent Vss and CLD decreasing with dose, but apparent clearance decreases only when the binding process produces drug elimination. The proposed model well captured the time-course of drug concentrations for the aldose reductase inhibitor imirestat, the endothelin receptor antagonist bosentan, and recombinant human interferon-β 1a. This type of model has a mechanistic basis and considerable utility for fully describing the kinetics for various doses of relevant drugs. [ABSTRACT FROM AUTHOR]

There is now considerable evidence to support a role for the endothelin (ET) system in the pathogenesis and progression of chronic heart failure (CHF). As such, the potential exists for this system to be useful in both diagnosis (by measurement of peptide levels in plasma and other body fluids) and treatment (by pharmacological blockade) of this condition. Plasma levels of endothelin-1 (ET-1) are elevated in CHF and the magnitude of elevation correlates with disease severity. ET-1 levels in plasma predict subsequent mortality in patients with CHF. ET-1 may also contribute to symptoms associated with CHF, such as exercise intolerance. In the diagnosis of CHF, plasma levels of ET-1 appear to be a less powerful discriminator between patients with mild disease and control subjects with normal ventricular function on multivariate analyses, compared to brain natriuretic peptide (BNP), or its N-terminal fragment. ET-1 concentrations are also elevated in the saliva of patients with CHF and may represent an alternative approach to assessment of the status of the ET system in these patients. Specific ET receptor antagonists (both mixed and ET(A)-selective) have been developed. Studies with these agents in animal models of CHF have demonstrated beneficial effects via both haemodynamic and non-haemodynamic pathways. A number of short-term clinical studies have been performed demonstrating improvements in haemodynamic parameters without neurohormonal activation. Long-term clinical studies with ET receptor antagonists are currently underway to definitively test the impact of blockade of this system on mortality and major cardiovascular endpoints. Endothelin converting enzyme (ECE) inhibitors represent an alternative strategy of ET blockade, and early data from animal models suggest these agents may be of clinical utility, either alone or, more likely, in combination with other zinc metallopeptidases. [ABSTRACT FROM AUTHOR]

The availability of potent and orally active nonpeptide endothelin (ET) receptor antagonists has generated a host of information on the pathophysiological role of ET-1 in a number of preclinical models including hypertension, renal failure, heart failure and pulmonary hypertension. Convincing data are available to show that ET-1 receptor antagonists are beneficial in humans as far as reversal of deranged systemic and regional hemodynamics associated with CHF and pulmonary hypertension. As in other disease areas, the issue of whether ET(A)-selective or ET(A/B) antagonists are more suited for CHF treatment remains unresolved. ET(B) receptors may mediate some critical processes in the kidney such as sodium and water excretion in addition to releasing vasodilator substances such as NO and prostacyclin from endothelial cells. In heart failure and chronic renal diseases, preservation of ET(B)-mediated responses in the kidney and pulmonary endothelium might be beneficial. On the other hand, blockade of ET(B)-mediated vasoconstriction, smooth muscle cell proliferation and fibrosis by ET(B) antagonists might be beneficial. In clinical trials so far, the hemodynamic effects of mixed antagonists of ET receptors and ET(A) selective antagonists seem equivalent. [ABSTRACT FROM AUTHOR]

A role of the potent and long-acting vasoconstrictor peptide endothelin-1 and the pathophysiology of chronic human heart failure has been postulated based upon indirect evidence such as elevated plasma endothelin-1 levels and their with the degree of hemodynamic impairment. The advent of specific of endothelin-1 receptor antagonists has provided the opportunity not only to directly evaluate its pathophysiological role but also to assess its potential role as a new approach to heart failure therapy. This brief review summarizes the evidence linking endothelin-1 to the pathophysiology of chronic heart failure and the clinical results obtained in patients during acute, intravenous and more prolonged, oral administration with bosentan, a mixed ET(A)/ET(B)-receptor antagonist. Bosentan acutely and during short-term oral therapy markedly improved hemodynamics in patients in addition to standard heart failure therapy, including an ACE-inhibitor. These effects were associated with a reduced responsiveness of the renin-angiotensin system to diuretic therapy and reduced basal plasma aldosterone levels. Although the hemodynamic and neurohumoral profile of short-term bosentan therapy looks promising for the treatment of patients with chronic heart failure appropriate trials will have to be performed to document clinical benefit during long-term therapy. Finally, the question remains open whether mixed endothelin-1 receptor antagonists like bosentan will have similar effects as compared to antagonists which block the ET(A) receptor only. [ABSTRACT FROM AUTHOR]

Endothelins are a family of potent endogenous mediators that have been implicated in a number of airway and other diseases. Recently, the non-peptide mixed ETA/ETB endothelin receptor antagonist bosentan has been successfully tested in the treatment of cardiovascular diseases. It was the aim of the present study to characterize the effects of bosentan on the pulmonary actions of endothelin-1 (ET-1), endothelin-3 (ET-3) and the ETB-receptor agonist IRL1620 in the isolated perfused and ventilated rat lung (IPL) and in precision-cut lung slices (PCLS). In the IPL, bosentan completely prevented the IRL1620-induced vasoconstriction (IC50 3 µM). The inhibition by bosentan of ET-1-elicited vasoconstriction showed a biphasic course, reflecting the inhibition of ETA- and ETB-mediated vasoconstriction (IC50 0.2 µM and 19 µM, respectively). In addition, bosentan prevented the ET-1- (IC50 6 µM) and IRL1620-induced (IC50 3 µM) prostacyclin release. Bosentan also completely prevented the bronchoconstriction induced by IRL1620 in the IPL (IC50 20 µM) and in PCLS (IC50 13 µM). In PCLS, the pD2-values were ET-1 7.20±0.23, ET-3 7.51±0.27 and IRL1620 7.33±0.29. Bosentan at 100 µM caused a rightward shift of the concentration-response curve of ET-1, ET-3 and IRL1620 by a factor of 5, 46 and 64, respectively. In all cases the slope of the Schild regression was lower than unity, disregarding a simple interaction of bosentan with one receptor. With respect to ET-1-induced bronchoconstriction, in the IPL bosentan in concentrations of up to 10 µM aggravated ET-1-induced bronchoconstriction probably due to the blockade of bronchodilatory ETA-receptors (IC50 0.3 µM) and even at 100 µM showed only very little protection from ET-1-induced bronchoconstriction in the IPL and in the PCLS. The similar IC50-values for ET-1-induced vasoconstriction and bronchodilation suggest that only one type of ETA-receptor is involved. The differing IC50-values between IRL1620-induced bronchoconstriction and prostacyclin release, the slope of the Schild regression and the failure of bosentan to prevent the ET-1-induced bronchoconstriction suggest a complex interaction between the known ET-receptors or the existence of unknown ETB-receptor subtypes. [ABSTRACT FROM AUTHOR]

Background. Severity of pancreatitis seems to be aggravated by impairment of vascular perfusion of the gland. Early mortality occurs within the first few days from the acute consequences of pancreatic injury with subsequent inflammatory response. Because vasoactive substances, including endothelin, seem to contribute to early mortality in acute pancreatitis, we tested the hypothesis that the inhibition of endothelin action could alter the outcome after severe experimental pancreatitis. Methods. In two groups of rats, pancreatitis was induced by intraductal infusion into the pancreatic duct of 1 µL/g body weight (b.w.) of either a 4% or a 5% sodium taurocholate solution. The mixed endothelin A and endothelin B receptor antagonist bosentan (20 mg/kg b.w.) or vehicle was injected intravenously in 12-h intervals for 3 d starting 1 h after induction of bile acid pancreatitis. This dose of bosentan is known to completely inhibit the effect of exogenous endothelin. The survival rate was monitored for 7 d. Thereafter, the surviving rats were sacrificed and the pancreas was prepared for histological and biochemical evaluation. Results. Irrespective of the treatment protocol (bosentan versus saline), survival was not different in animals challenged with either 4% or 5% sodium taurocholate. The corresponding survival rates were 62% with bosentan and 77% without bosentan in the 4% sodium taurocholate group. In the 5% sodium taurocholate group, the survival rates were 20% with and 27% without bosentan. Morphological and biochemical alterations were identical in control as well as in endothelin-antagonist-treated rats. Conclusion. Therapy with the mixed endothelin A and endothelin B receptor antagonist bosentan does not influence the outcome after severe experimental pancreatitis. Therefore, blockade of endothelin A and B receptor subtypes may not be of major importance as a therapeutic principle in this model of experimental pancreatitis. [ABSTRACT FROM AUTHOR]