List of products in the National Drug Code with proprietary name . Ambrisentan is used to treat high blood pressure in the lungs (pulmonary arterial hypertension). This condition is thought to be caused by increased levels of a certain natural substance (endothelin-1). This medication blocks the effects of endothelin-1, thereby helping to decrease the blood pressure in the lungs, slow the worsening of symptoms, and improve your ability to exercise.