List of products in the National Drug Code with proprietary name . This medication is used to treat a type of high blood pressure in the lungs (pulmonary arterial hypertension). Treprostinil helps to delay disease worsening and increase your ability to exercise. It works by relaxing and widening the blood vessels (arteries) in the lungs and other parts of the body so that blood can flow more easily. This medication belongs to a class of drugs known as vasodilators.