Overview Assess the Efficacy and Safety of Sildenafil When Added to Bosentan in the Treatment of Pulmonary Arterial Hypertension Status: Completed Trial end date: 2013-08-01 Target enrollment: Participant gender: Summary To assess the efficacy and safety of sildenafil when added to patients with PAH who are taking bosentan as all or part of their background therapy. Phase: Phase 4 Details Lead Sponsor: PfizerPfizer's Upjohn has merged with Mylan to form Viatris Inc.Treatments: BosentanSildenafil Citrate