Side effects were common and rarely enough to make men stop
Pooled across the randomised trials, flushing affected 12% of men, headache 11%, indigestion 5% and visual disturbance 3%, each significantly above placebo.
What the study found
Side effects were common and no likelier than placebo to end a trial
Pooled across the randomised trials, flushing affected 12% of men on sildenafil, headache 11%, indigestion 5% and visual disturbance 3%, each significantly above placebo. Men taking sildenafil were nonetheless no likelier than men on placebo to leave a trial because of a side effect.
The caveat · Rare, serious effects went uncounted
These are the frequent and mild ones, gathered over about twelve weeks. The rare and serious events the label warns about, an erection lasting beyond four hours among them, are too uncommon for trials this size to count, so their absence here is not evidence of their absence.