RECORD STATUS: None CITATION: Robinette B. Bosentan (Tracleer) University HealthSystem Consortium (UHC). Drug Monograph. 2002

RECORD STATUS: None CITATION: Canadian Coordinating Office for Health Technology Assessment. Bosentan. Canadian Coordinating Office for Health Technology Assessment (CCOHTA). 2002

OBJECTIVE: In order to provide an overview of current knowledge, the literature was systematically examined for clinical studies, which evaluate the safety and effectiveness of bosentan in pediatric pulmonary arterial hypertension (PAH). SOURCES: 3 databases (MEDLINE, EMBASE and BIOSIS) were searched for the period January 2000 - October 2007 using the key words 'pulmonary arterial hypertension', 'bosentan', and 'pediatric patients/children'. RESULTS: Of 165 identified publications, 21 clinical studies were selected: 1 interventional prospective, 6 observational prospective, 5 observational retrospective, and 9 case reports/case series. In the absence of controlled trials, these 21 studies represent the current evidence on the effectiveness and safety of bosentan in the treatment of pediatric PAH. Bosentan appears to improve long-term functional status and hemodynamics in children with PAH but improvement in exercise capacity is not consistently demonstrated. Promising results are reported for the combination of bosentan with other PAH-specific treatments although guidelines for instituting combination therapy have not been defined. Overall, no safety concern is raised by these studies; adverse events, including liver enzyme elevations, appear to be less frequent than reported in the adult PAH clinical trials. CONCLUSION: Recent experience, although uncontrolled, suggests that bosentan is a well-tolerated and effective therapy for pediatric PAH.

BACKGROUND: Endothelin is a powerful vasoconstrictor peptide derived from the endothelium. We evaluated the contribution of endothelin to blood-pressure regulation in patients with essential hypertension by studying the effect of an endothelin-receptor antagonist, bosentan. METHODS: We studied 293 patients with mild-to-moderate essential hypertension. After a placebo run-in period of four to six weeks, patients were randomly assigned to receive one of four oral doses of bosentan (100, 500, or 1000 mg once daily or 1000 mg twice daily), placebo, or the angiotensin-converting-enzyme inhibitor enalapril (20 mg once daily) for four weeks. Blood pressure was measured before and after treatment. RESULTS: As compared with placebo, bosentan resulted in a significant reduction in diastolic pressure with a daily dose of 500 or 2000 mg (an absolute reduction of 5.7 mm Hg at each dose), which was similar to the reduction with enalapril (5.8 mm Hg). There were no significant changes in heart rate. Bosentan did not result in activation of the sympathetic nervous system (as determined by measurement of the plasma norepinephrine level) or the renin-angiotensin system (as determined by measurements of plasma renin activity and angiotensin II levels). CONCLUSIONS: An endothelin-receptor antagonist, bosentan, significantly lowered blood pressure in patients with essential hypertension, suggesting that endothelin may contribute to elevated blood pressure in such patients. The favorable effect of treatment with bosentan on blood pressure occurred without reflexive neurohormonal activation.

The dual endothelin receptor antagonist bosentan has been approved in several countries for pulmonary arterial hypertension, and patients with portopulmonary hypertension (PPHTN) have not specifically been excluded. However, no data have been published on the efficacy and safety of bosentan in this patient population. Here, the first clinical experiences with bosentan in patients with Child A cirrhosis and severe PPHTN are reported. In total, 11 consecutive patients with cirrhosis and severe PPHTN in New York Heart Association Functional Classes III and IV were treated for >1 yr with bosentan. After 1 yr of treatment with bosentan, all patients showed improved symptoms and exercise capacity. The 6-min walking distance increased from 310+/-102 m at baseline to 388+/-81 m at 1 yr. Cardiopulmonary exercise testing disclosed a significant increase in peak oxygen uptake, from 12.6+/-3.5 to 16.6+/-2.8 mL.min(-1).kg(-1). Pulmonary vascular resistance fell from 944+/-519 to 635+/-321 dynes.s.L(-1). The medication was well tolerated by all patients, and there was no evidence of drug-related liver injury. In conclusion, bosentan proved to be efficacious and safe in a small number of patients with portopulmonary hypertension.

Tadalafil, an oral phosphodiesterase 5 (PDE5) inhibitor, is being investigated as a treatment for pulmonary arterial hypertension. Bosentan is an oral endothelin receptor antagonist widely used in the treatment of pulmonary arterial hypertension. Tadalafil is mainly metabolized by cytochrome P450 (CYP) 3A4, and as bosentan induces CYP2C9 and CYP3A4, a pharmacokinetic interaction is possible between these agents. This open-label, randomized study investigated whether any pharmacokinetic interaction exists between tadalafil and bosentan. Healthy adult men (n = 15; 19-52 years of age) received 10 consecutive days of tadalafil 40 mg once daily, bosentan 125 mg twice daily, and a combination of both in a 3-period, crossover design. Following 10 days of multiple-dose coadministration of bosentan and tadalafil, compared with tadalafil alone, tadalafil geometric mean ratios (90% confidence interval [CI]) for AUCtau and Cmax were 0.59 (0.55, 0.62) and 0.73 (0.68, 0.79), respectively, with no observed change in tmax. Following coadministration of bosentan with tadalafil, bosentan ratios (90% CI) for AUCtau and Cmax were 1.13 (1.02, 1.24) and 1.20 (1.05, 1.36), respectively. Tadalafil alone and combined with bosentan was generally well tolerated. In conclusion, after 10 days of coadministration, bosentan decreased tadalafil exposure by 41.5% with minimal and clinically irrelevant differences (<20%) in bosentan exposure.

Pulmonary hypertension during exercise is common in severe chronic obstructive pulmonary disease (COPD). It was hypothesised that the use of the endothelin-receptor antagonist bosentan can improve cardiopulmonary haemodynamics during exercise, thus increasing exercise tolerance in patients with severe COPD. In the present double-blind, placebo-controlled study, 30 patients with severe or very severe COPD were randomly assigned in a 2:1 ratio to receive either bosentan or placebo for 12 weeks. The primary end-point was change in the 6-min walking distance. Secondary end-points included changes in health-related quality of life, lung function, cardiac haemodynamics, maximal oxygen uptake and pulmonary perfusion patterns. Compared with placebo, patients treated with bosentan during 12 weeks showed no significant improvement in exercise capacity as measured by the 6-min walking distance (mean+/-SD 331+/-123 versus 329+/-94 m). There was no change in lung function, pulmonary arterial pressure, maximal oxygen uptake or regional pulmonary perfusion pattern. In contrast, arterial oxygen pressure dropped, the alveolar-arterial gradient increased and quality of life deteriorated significantly in patients assigned bosentan. The oral administration of the endothelin receptor antagonist bosentan not only failed to improve exercise capacity but also deteriorated hypoxaemia and functional status in severe chronic obstructive pulmonary disease patients without severe pulmonary hypertension at rest.

BACKGROUND: Endothelin-1 is a potent vasoconstrictor and smooth-muscle mitogen. In a preliminary study, the orally administered dual endothelin-receptor antagonist bosentan improved exercise capacity and cardiopulmonary hemodynamics in patients with pulmonary arterial hypertension. The present trial investigated the effect of bosentan on exercise capacity in a larger number of patients and compared two doses. METHODS: In this double-blind, placebo-controlled study, we randomly assigned 213 patients with pulmonary arterial hypertension (primary or associated with connective-tissue disease) to receive placebo or to receive 62.5 mg of bosentan twice daily for 4 weeks followed by either of two doses of bosentan (125 or 250 mg twice daily) for a minimum of 12 weeks. The primary end point was the degree of change in exercise capacity. Secondary end points included the change in the Borg dyspnea index, the change in the World Health Organization (WHO) functional class, and the time to clinical worsening. RESULTS: At week 16, patients treated with bosentan had an improved six-minute walking distance; the mean difference between the placebo group and the combined bosentan groups was 44 m (95 percent confidence interval, 21 to 67; P<0.001). Bosentan also improved the Borg dyspnea index and WHO functional class and increased the time to clinical worsening. CONCLUSIONS: The endothelin-receptor antagonist bosentan is beneficial in patients with pulmonary arterial hypertension and is well tolerated at a dose of 125 mg twice daily. Endothelin-receptor antagonism with oral bosentan is an effective approach to therapy for pulmonary arterial hypertension.

Novel treatments, such as prostanoids or endothelin receptor antagonists, have been introduced for various forms of pulmonary arterial hypertension, but the long-term effects of these treatments on portopulmonary hypertension (PPHT) are unknown. In a retrospective analysis, the present authors assessed the safety and efficacy of inhaled iloprost, a prostacyclin analogue, and bosentan, an endothelin receptor antagonist, in patients with PPHT. In total, 31 consecutive patients with Child class A or B cirrhosis and severe PPHT were treated for up to 3 yrs with either inhaled iloprost (n = 13) or bosentan (n = 18), and the effects on exercise capacity, haemodynamics and survival were evaluated. In the iloprost group, the survival rates at 1, 2 and 3 yrs were 77, 62 and 46%, respectively. In the bosentan group, the respective survival rates were 94, 89 and 89%. Event-free survival rates, i.e. survival without transplantation, right heart failure or clinical worsening requiring the introduction of a new treatment for pulmonary hypertension, was also significantly better in the bosentan group. Bosentan had significantly better effects than inhaled iloprost on exercise capacity, as determined by the 6-min walk test, as well as on haemodynamics. Both treatments proved to be safe, especially in regards of liver function. In the present series of patients with well-preserved liver function and severe portopulmonary hypertension, treatment with both inhaled iloprost and bosentan appeared to be safe. Patients treated with bosentan had higher survival rates, but prospective controlled studies are required to confirm these findings.

Data on treatment of patients with portopulmonary hypertension (PoPH) are limited, as they are usually excluded from randomised controlled trials with pulmonary arterial hypertension (PAH)-specific therapies. This study investigated the short- and long-term efficacy/safety of bosentan in these patients, as well as its pharmacokinetics. All 34 consecutive patients with PoPH treated with first-line bosentan (December 2002 to July 2009) were retrospectively evaluated. Assessments included the New York Heart Association functional class (NYHA FC), blood tests, haemodynamics, 6-min walk distance (6MWD) and event-free status. The pharmacokinetics of bosentan in five patients with Child-Pugh (C-P) class B cirrhosis were compared with idiopathic PAH patients. Significant improvements from baseline were observed in NYHA FC, 6 MWD and haemodynamics, and were largely maintained during follow-up. Patients with C-P class B cirrhosis (n=9) had significantly larger haemodynamic improvement after mean ± SD 5 ± 2 months. Mean follow-up time was 43 ± 19 months; four patients died and seven patients had significant elevation of liver enzymes (annual rate 5.5%). Plasma concentrations of bosentan were higher in patients with C-P class B cirrhosis than those observed in idiopathic PAH. These data confirm the benefit of bosentan treatment for patients with PoPH. Haemodynamic improvements were particularly pronounced in patients with more severe cirrhosis. The safety profile of bosentan was consistent with previous studies.