Overview To Assess The Efficacy and Safety Of Oral Sildenafil in the Treatment of Pulmonary Arterial Hypertension. Status: Terminated Trial end date: 2010-05-25 Target enrollment: Participant gender: Summary To demonstrate a dose response for 1 mg, 5 mg and 20 mg TID oral sildenafil for the treatment of subjects with PAH. Phase: Phase 4 Details Lead Sponsor: PfizerPfizer's Upjohn has merged with Mylan to form Viatris Inc.Treatments: Citric AcidSildenafil CitrateSodium Citrate