Overview Use of Sildenafil (Viagra) to Alter Fatigue, Functional Status and Impaired Cerebral Blood Flow in Patients With CFS Status: Completed Trial end date: 2010-12-01 Target enrollment: Participant gender: Summary Use of Viagra to Alter Symptoms in Patients with Chronic Fatigue Syndrome (CFS) Phase: Phase 4 Details Lead Sponsor: Charles Drew University of Medicine and ScienceCollaborator: PfizerTreatments: Sildenafil Citrate