(R)-AMbrisentan 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 functions as an endothelin receptor antagonist, specifically targeting the endothelin type-A receptors. By blocking these receptors, it helps to relax the blood vessels in the lungs, thereby reducing blood pressure and improving the ability to exercise. This medication is often prescribed to enhance exercise capacity and delay clinical worsening in patients with PAH, particularly those classified as WHO Functional Class II or III. It is typically administered orally, making it a convenient option for long-term management of the condition. (R)-AMbrisentan is usually part of a comprehensive treatment plan that may include other therapies tailored to the patient's specific needs. Regular monitoring is essential to assess its effectiveness and manage any potential side effects.