Question 1

If I take Cialis at 8pm, when will it be most effective?

Accepted Answer

Peak concentration occurs around 10pm, and it remains effective through the next day and into the following evening – up to 36 hours total.

Question 2

How long after stopping Cialis does it leave my system completely?

Accepted Answer

Cialis has a half-life of 17.5 hours, so it takes about 5-6 days to be completely eliminated.

Question 3

Does food affect how quickly Cialis starts working?

Accepted Answer

Food may slightly delay absorption (by about 1 hour) but does not reduce overall effectiveness. You can take it with or without food.

Question 4

Why can Cialis work for 36 hours when its half-life is 17.5 hours?

Accepted Answer

Because the concentration needed for PDE5 inhibition in the penis is much lower than peak levels. Even as plasma levels drop, they remain above the therapeutic threshold for up to 36 hours.