Bosentan is primarily used in the treatment of pulmonary arterial hypertension (PAH), a condition characterized by high blood pressure in the arteries of the lungs. It works by blocking the action of endothelin, a substance that narrows blood vessels, thereby helping to relax and widen these vessels. This improves blood flow and reduces the strain on the heart, alleviating symptoms such as shortness of breath and fatigue. It is often prescribed to improve exercise capacity and delay clinical worsening in patients with PAH. Additionally, bosentan may be used in combination with other therapies to manage the progression of the disease. Regular monitoring of liver function is required during treatment due to potential side effects.