Chronic Fatigue Syndrome 2009 NCRR 3P20RR011145-14S2 6918 CLINICAL TRIAL: USE OF VIAGRA TO ALTER SYMPTOMS IN PTS WITH CFS FRIEDMAN, THEODORE CHARLES R. DREW UNIVERSITY OF MED & SCI CA $1,597
Viagra (under another trade name) is used in treatment of pulmonary arterial hypertension (a relatrively rare condition), so it is good for some selected cardiovascular diseases. And Pfizer does continue to look at new uses, because believe it or not, the ED drug market has sort of leveled off - sales have not continued to increase after the initial excitement (heh heh) over the introduction of ED drugs.
I'm a little stumped as to what "PTS" means in the above listing, but here is the full listing from clinicaltrials.gov about the study.
The principal aim of this study is to determine whether chronic fatigue syndrome (CFS) is due to inadequate blood flow to the brain and to test a medication, Viagra, which should help increase blood flow to the brain and improve the symptoms of CFS. [ Time Frame: 6 weeks ]