Overview Randomized, Controlled Trial of Regular Sildenafil Citrate in the Prevention of Altitude Illness Status: Completed Trial end date: 2008-02-01 Target enrollment: Participant gender: Summary The purpose of this study is to determine whether regular oral use of sildenafil citrate can prevent or attenuate high altitude illnesses. Phase: Phase 4 Details Lead Sponsor: Altitude Physiology ExpeditionsCollaborator: University of EdinburghTreatments: Citric AcidSildenafil Citrate