Macitentan 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 endothelin receptors, which helps to relax blood vessels and improve blood flow, thereby reducing the strain on the heart. This medication is often prescribed to enhance exercise capacity and delay disease progression in patients with PAH. It is typically administered orally, making it convenient for long-term management of the condition. Macitentan is also studied for its potential benefits in other conditions involving vascular dysfunction, though its primary application remains in PAH therapy.