List of products in the National Drug Code with proprietary name . Macitentan 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, which helps decrease the blood pressure in the lungs, and reduces the risk of worsening of symptoms and hospital stays due to the disease.