I used a high dose of Viagra on Friday night. To high apparently. all light turn kind of light blue and was enhanced a pit. SOooo for comparison sake I took some Cialis on Saturday. This stuff is way better. No side effect that I could tell. Maybe stuffiness in the nose however that could of been from the Viagra. Anyway, Think Ill toss the V in the drawer for a while. THe cialis is by far the better of the two.