How does bosentan work?
Bosentan works by blocking the effects of a substance called endothelin, which is made by the body in increased amounts in patients with PAH. Endothelin causes blood vessels to narrow (constrict). It also causes scarring and overgrowth of the muscle in the walls of the blood vessels in the lungs. By blocking the action of endothelin, bosentan can lead to a reduction in the blood pressure in the lungs and to improvement in activity level and wellbeing. Improved exercise capacity and increased sense of wellbeing have been demonstrated in short-term studies of Tracleer. Open label studies suggest favorable long-term results in many patients, with some patients requiring addition of or change to other therapies. A recent study suggested that it may improve survival in NYHA class III patients compared to historical controls. Another recent study shows that it delays time to clinical worsening in NYHA class II patients. It has also been shown to improve 6 minute walk distance and hemodynamic
