15(R)-Iloprost 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 dilating these arteries, reducing the strain on the heart and improving blood flow. This helps alleviate symptoms such as shortness of breath, fatigue, and chest pain, enhancing the patient’s quality of life. Additionally, it is used to manage severe cases of Raynaud's phenomenon, where it improves blood circulation in the extremities, reducing pain and preventing tissue damage. Its vasodilatory and antiplatelet properties make it a valuable therapeutic agent in these conditions.