 Ambrisentan is an endothelin receptor antagonist used for the treatment of pulmonary hypertension PH. Based on research suggesting a role for endothelin-1 in the pathogenesis of idiopathic pulmonary fibrosis IPF and the poor prognosis for patients with IPF who are also diagnosed with PH, this study was designed to evaluate the effectiveness and safety of ambrisentan in that patient population. 