Prostacyclines are most often used to treat pulmonary arterial hypertension (PAH). Prostacyclines work by relaxing blood vessels and reducing blood pressure in the lungs, which helps improve your ability to exercise and breathe. These medications come in different forms, including oral tablets, injections, and inhaled formulations. Examples include epoprostenol (Flolan, Veletri), treprostinil (Remodulin, Tyvaso, Orenitram), and iloprost.