- High blood pressure in the lungs, known as pulmonary arterial hypertension (PAH), is a rare disorder. In spite of recent advances in treatment, the death rate remains unacceptably high. Lung blood vessel function can be harmed by progressive injuries, such as inflammation, leading to worsening of the disease. A drug called spironolactone has been known to improve blood vessel function and reduce inflammation. Some people with PAH take spironolactone to help treat fluid retention. However, its effect on inflammation and blood vessel function in patients withPAH is not known. Researchers want to see if spironolactone can help these conditions in people with PAH.