Sildenafil for Pulmonary Arterial Hypertension

High-altitude Hypoxia Influences the Activities of the Drug-Metabolizing Enzyme CYP3A1 and the Pharmacokinetics of Four Cardiovascular System Drugs

(1) Background: High-altitude hypoxia has been shown to affect the pharmacokinetic properties of drugs. Although there is a high incidence of cardiovascular disease among individuals living in high-altitude areas, studies on the effect of high-altitude hypoxia on the pharmacokinetic properties of cardiovascular drugs are limited. (2) Methods: The aim of this study was to evaluate the pharmacokinetics of nifedipine, bosentan, simvastatin, sildenafil, and their respective main metabolites, dehydronifedipine, hydroxybosentan, simvastatin hydroxy acid, and N-desmethyl sildenafil, in rats exposed to high-altitude hypoxia. Additionally, the protein and mRNA expression of cytochrome P450 3A1 (CYP3A1), a drug-metabolizing enzyme, were examined. (3) Results: There were significant changes in the pharmacokinetic properties of the drugs in rats exposed to high-altitude hypoxia, as evidenced by an increase in the area under the curve (AUC) and the half-life (t_1/2z) and a decrease in total plasma clearance (CL_z/F). However, most of these changes were reversed when the rats returned to a normoxic environment. Additionally, there was a significant decrease in CYP3A1 expression in rats exposed to high-altitude hypoxia at both the protein and mRNA levels. (4) Conclusions: High-altitude hypoxia suppressed the metabolism of the drugs, indicating that the pharmacokinetics of the drugs should be re-examined, and the optimal dose should be reassessed in patients living in high-altitude areas.

Pulmonary arterial hypertension associated to connective tissue diseases

Pulmonary arterial hypertension is a well-known complication of connective tissue diseases such as systemic sclerosis, systemic lupus erythematosus, mixed connective tissue diseases, and to a lesser extent, rheumatoid arthritis, dermatopolymyositis and primary Sjögren’s syndrome. In these patients, pulmonary hypertension may occur in association with left heart disease, interstitial fibrosis or as a result of a isolated pulmonary arteriopathy. The incidence of pulmonary arterial hypertension in the limited form of systemic sclerosis is about 10%. The pathophysiologic mechanisms leading to pulmonary arterial hypertension remain unknown. Symptoms and clinical presentation are very similar to idiopathic pulmonary arterial hypertension but mortality was confirmed to be higher. Echocardiography is the reference investigation for the detection of pulmonary arterial hypertension but the results should be confirmed by right heart catheterization. Treatment appears more complex as compared to idiopathic pulmonary arterial hypertension. Intravenous epoprostenol therapy has been shown to be effective in a special trail. Also, the endothelin receptor antagonists bosentan and sitaxentan, the phosphodyesterase-type-5 sildenafil and subcutaneous treprostinil have shown favourable results.

Idiopathic- and scleroderma-related pulmonary arterial hypertension: outcomes and QOL on bosentan

Idiopathic pulmonary arterial hypertension (previously known as primary pulmonary hypertension) is a devastating disease of insidious onset, late diagnosis, progressive functional disability and poor prognosis. However, treatment with pulmonary arterial hypertension-specific agents has already changed the outlook wherever these agents are accessible. The process of economic evaluation of treatment for idiopathic pulmonary arterial hypertension is challenging due to limitations common to clinical studies in rare diseases, such as small patient numbers limiting survival information, lack of directly comparable trials for the efficacy of different drugs and a paucity of quality of life measurements. Bosentan (Tracleer), Actelion), has proven effective in clinical trials, and is the most frequently used pulmonary arterial hypertension-specific agent worldwide. It has additionally undergone a comprehensive quality of life trial and economic evaluation as therapy for idiopathic pulmonary arterial hypertension and pulmonary arterial hypertension associated with scleroderma. This review explores the role of bosentan in providing cost-effective therapy compared with alternative treatments, and addresses the future considerations required to ensure accessible patient care for idiopathic pulmonary arterial hypertension and pulmonary arterial hypertension associated with scleroderma.

Bosentan therapy of pulmonary arterial hypertension in connective tissue diseases

BACKGROUND

Pulmonary arterial hypertension (PAH) is a life-threatening and debilitating complication of several connective tissue diseases. We aimed to evaluate the effects of long-term treatment with bosentan, an oral dual endothelin ET(A)/ET(B) receptor antagonist, in a cohort of patients with PAH related to connective tissue diseases.

MATERIALS AND METHODS

In the present prospective, noncontrolled study, 13 patients (nine with systemic sclerosis, two with systemic lupus erythematosus, one with mixed connective tissue disease and one with overlap syndrome including scleroderma and myositis), mostly nonresponders to prostanoids therapy, were treated for 1 year with bosentan. Cardiac haemodynamics and the diagnosis of PAH were performed by Doppler ultrasound examination. Exercise capacity was assessed by 6-min walking test at baseline and at 3, 6 and 12 months of therapy.

RESULTS

During bosentan treatment, progressive improvement of exercise capacity was observed. Walk distance increased in seven patients, remained unchanged in three and slightly decreased in three patients. A progressive significant decrease of right ventricular systolic pressure was also observed, whereas pulmonary artery mean pressure remained unchanged. Adverse effects related to bosentan (elevation of hepatic aminotransferases) were noted in two patients.

CONCLUSION

Long-term treatment with bosentan was effective in improving exercise capacity and pulmonary haemodynamics in patients with PAH related to connective tissue diseases.

Connective tissue associated pulmonary arterial hypertension

The number of publications in the field of pulmonary hypertension has increased exponentially over the past 10 years. As a consequence our understanding of the condition has advanced enormously. Pulmonary hypertension is now recognised as an uncommon and treatable disease, rather than a rare lethal disease. Progress in the field of connective tissue disease associated pulmonary hypertension has been less consistent. This paper covers the most influential published data on connective tissue associated pulmonary hypertension, and adds some insights from data available on file with pharmaceutical companies and from our database at the Royal Free Hospital. The following conclusions may be drawn. First, the prevalence of pulmonary hypertension associated with connective tissue diseases is lower than generally accepted. Second, the natural history and prognosis, at least in the setting of systemic sclerosis, is worse than seen in patients with idiopathic pulmonary hypertension. Finally, widespread and timely availability of disease modifying therapies substantially improves the prognosis for patients with systemic sclerosis associated pulmonary hypertension, in the treatment population and consequentially in the population as a whole. Identifying patients with very early disease and analysing the drivers for disease progression, is the key to further progress. Early diagnosis is most readily achieved in patients with connective tissue disease associated pulmonary hypertension. This represents an opportunity for those with an interest in academic rheumatology.

Clinical and Immunoserological Characteristics of Mixed Connective Tissue Disease Associated with Pulmonary Arterial Hypertension

We investigated the clinical characteristics and immunoserological alterations in patients with mixed connective tissue disease (MCTD) associated with pulmonary arterial hypertension (PAH). Anti-U1RNP autoantibodies, anti-endothelial cell antibodies (AECA) and serum thrombomodulin (TM) as well as von Willebrand factor antigen (vWFAg) concentrations were measured in 25 patients with MCTD associated with PAH and in 154 MCTD patients without PAH. The results showed that the probability of survival was lower in MCTD patients with PAH than in the 154 MCTD-non-PAH patients (5-year survival rate in MCTD with PAH: 73%, versus 96% in MCTD-non-PAH; P < 0.01). AECA were more frequently present in the sera of MCTD patients with PAH than in MCTD-non-PAH (P < 0.001). Serum TM and vWFAg levels were higher in MCTD-PAH patients than in MCTD-non-PAH patients (TM: P < 0.001; vWFAg: P < 0.001). Significant correlation was noticed between the quantity of AECA and TM level (r = 0.466) as well as the quantity of AECA and vWFAg level (r = 0.550). In conclusion, our results suggest that in MCTD the presence of AECA and endothelial cell activation may play a role in the development of PAH and in the maintenance of obliterative vascular processes.

Beraprost therapy in children with pulmonary hypertension secondary to congenital heart disease

We present a report on children with severe pulmonary hypertension secondary to congenital heart disease who received 6 months of beraprost therapy. The children had an increase in intracardiac left-to-right shunt and a reduction of the pulmonary-to-systemic vascular resistance ratio, whereas the pulmonary artery pressure was not significantly changed.

Tratamento da hipertensão arterial pulmonar

O desenvolvimento de novas alternativas terapêuticas, principalmente na última década, possibilitou uma mudança significativa na evolução dos pacientes portadores de hipertensão arterial pulmonar. Essa mudança reflete-se não apenas em uma melhor qualidade de vida, mas também no aumento da sobrevida desses pacientes. Embora ainda existam inúmeros estudos em andamento, avaliando opções terapêuticas novas e ainda a associação de diferentes classes de medicamentos, o desenvolvimento atual já permitiu a definição de algoritmos de tratamento baseados no que existe de evidência documentada, fato que certamente já traz impacto importante na padronização e otimização dos recursos terapêuticos.

Bosentan therapy for pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) is characterized by the progressive increase in pulmonary vascular resistance potentially leading to right heart failure and death. Since endothelins may play a pathogenic role in the development of the disease, endothelin receptor antagonists have been proposed for the treatment of this condition. Bosentan (Tracleer®), an oral nonselective ETA/ETB endothelin receptor antagonist, has been shown to improve exercise capacity, quality of life and hemodynamics of patients with PAH in short-term trials. These improvements were sustained and a long-term observational study on idiopathic PAH patients suggested a favorable effect on survival in this subset. The present report summarizes the pharmacology, clinical efficacy and safety profile of bosentan with an overview of the current therapies available for the treatment of PAH.

Sildenafil: Emerging Cardiovascular Indications

The discovery in 1989 of sildenafil, a highly selective inhibitor of phosphodiesterase-5 (PDE-5), was the result of extensive research on chemical agents targeting PDE-5 that might potentially be useful in the treatment of coronary heart disease. Initial clinical studies on sildenafil in the early 1990s were not promising with respect to its antianginal potential. However, the incidental discovery of its antiimpotence effect led to its approval of for the treatment of erectile dysfunction. Thereafter, several reports of adverse cardiac events in patients on sildenafil raised concerns about its safety in cardiovascular disorders. Novel therapeutic indications are emerging for sildenafil with the recent discovery that PDE-5 is expressed in various other tissues such as the arterial vasculature, including pulmonary and coronary arteries, venous vasculature, skeletal muscles, platelets, and visceral and tracheobronchial muscles. In this review we briefly summarize the pharmacology of sildenafil and the current available evidence on its potential therapeutic applications in cardiovascular disorders.

[Pulmonary hypertension: from genetics to treatments]

Pulmonary hypertertension (PHT) is a rare disease defined by increased resistance of the pulmonary arteries inevitably leading to right heart failure if specific treatment is not given. This disease can occur sporadically (idiopathic or primary PHT), within a familial context (familial PHT, BMPR2 gene mutation), or occur as a complication of other diseases (connective tissue disease, congenital cardiomyopathy, human immunodeficiency virus infection, portal hypertension, use of anorexigenic agents). The incidence of primary PHT is 2 million cases per year, probably an underestimation due to the low specificity of clinical signs, predominantly exercise-induced dyspnea. Recent therapeutic advances (prostacyclin and endothelin receptor antagonists administered in continuous infusion) have improved the prognosis of this orphan disease. Inhaled iloprost and type 5 phosphodiesterase inhibitors should be evaluated for this indication. Lung transplantation is reserved for patients unresponsive to medical treatment.