A Research Study To Assess The Effectiveness And Safety Of Different Doses Of Oral PF-00489791 In The Treatment Of Adult Patients With Pulmonary Arterial Hypertension

Exclusion Criteria

• •pulmonary arterial hypertension (PAH)other than idiopathic or familial
• •For females, pregnancy or lactation
• •Use of specific PAH treatments, potent CYP3A4 inhibitors, protease inhibitors, alpha blockers or arginine 30 days prior tio randomization and during the study
• •Change of dose or class of standard background PAH therapy, i.e. oxygen, calcium channel blockers, digoxin, diuretics 30 days prior tio randomization and during the study
• •Large shift in altitude (defined as \>5000 feet or 1524 meters) during 90 days prior to baseline visit and/or during the study visit
• •Subjects with intracardiac shunts and/or serious heart, lung or other health conditions
• •HIV positive subjects
• •Subjects participating in another clinical trial with an investigational drug or device
• •Subjects with degenerative retinal disorders, history of non-arteritic anterior ischemic optic neuropathy or untreated proliferative diabetic retinopathy
• •Allergies and previous intolerance of PDE5 inhibitors
• •Alcohol or drug abuse
• •Blood donation during the study, or 1 month before or after the study