Just over half of attempts worked on sildenafil, a fifth on placebo
Across 27 trials and 6,659 men, 57% of attempts succeeded on sildenafil against 21% on placebo. Counted per man over a whole trial, 83% had at least one success against 45%.
What the study found
Sildenafil roughly tripled the share of attempts that worked
Two different numbers get quoted here and they measure different things. Across 27 randomised trials and 6,659 men, 57% of intercourse attempts succeeded on sildenafil against 21% on placebo; counted per man over a whole trial, 83% had at least one success against 45%.
The caveat · Mostly mild to moderate cases
Enrolled men skewed towards mild and moderate erectile dysfunction, so these figures sit at the optimistic end of what an unselected clinic sees. Success was recorded by the men themselves, in diaries. Most trials ran about twelve weeks, and almost all were funded by the manufacturer.