More Info About our Xcite Viagra Viagra is used to treat erectile dysfunction by enhancing an erection when a male is aroused. It does so by increasing overall blood flow, sending more blood into the penis. The effects of Viagra can last up to 4 hours. Common side effects: Headaches Flushing of the face Indigestion Nasal congestion Recommended dose: 25mg (half a tablet)- 50mg (entire tablet) per day 30 minutes-4 hours prior to sexual activity