Tracleer, generically known as bosentan, is a prescription medication primarily used in the treatment of pulmonary arterial hypertension (PAH), a condition characterized by high blood pressure in the arteries that supply blood to the lungs. By blocking endothelin receptors, Tracleer helps to dilate blood vessels in the lungs, reducing blood pressure and improving symptoms such as shortness of breath and exercise capacity. This medication belongs to a class of drugs known as endothelin receptor antagonists. It is important for patients to be closely monitored while on Tracleer due to potential liver side effects and the risk of harm to an unborn baby if taken during pregnancy. Therefore, Tracleer is often prescribed with specific safety monitoring and under a special program that includes pregnancy testing and the use of effective birth control for women of childbearing age.