How quickly does tadalafil work after administration?

In a study using stopwatch methodology, tadalafil  20 mg facilitated an erectile response 16  minutes post-dose (p = 0.012 versus placebo)  and tadalafil 10 mg facilitated an erectile  response within 30 minutes post-dose  (p = 0.042 versus placebo) [30]. These results  are similar to those found for vardenafil HCl  (16 minutes) and sildenafil citrate (14 minutes)  [31,32]. However, it is important to note that  the majority of men do not respond at these  early time points. In all three studies, about  one-third of men respond at these early time  points. Most men will require more time to  achieve an erection sufficient for vaginal penetration  and intercourse.