Prostacyclin agonists are used to treat pulmonary arterial hypertension (PAH). These medications work by mimicking the effects of prostacyclin, a natural substance in your body that widens blood vessels. This helps improves blood flow and lowers blood pressure in the lungs. Prostacyclin agonists come in different forms, including oral tablets and injectable solutions. A main example is Uptravi (selexipag).