Safety and Efficacy of Sitaxsentan in the Treatment of Pulmonary Arterial Hypertension

Inclusion Criteria: 1. NYHA Class II, III or IV 2. 16 to 75 years of age 3. Specific peak VO2 range 4. PPH, PAH due to connective tissue disease or select congenital heart disease 5. Qualifying cardiac catheterization 6. History of CXR and qualifying pulmonary function test 7. History of qualifying ventilation-perfusion lung scan 8. History of qualifying echocardiogram 9. Women of childbearing potential must use contraceptives 10. Stable dose of corticosteroids if prescribed Exclusion Criteria: 1. Significant lung disease 2. Chronic liver disease 3. Uncontrolled sleep apnea 4. History of specific types of left heart disease 5. Any disorder that compromises ability to give informed consent 6. Uncontrolled sleep apnea 7. Inability to perform bicycle exercise test 8. On-going treatment with an experimental drug or device within the last 30 days 9. HIV infection 10. Specific liver dysfunction 11. Chronic renal disease 12. Pregnancy/Nursing 13. Chronic active hepatitis B or C 14. Chronic Flolan or Tracleer use within the last 30 days