Sildenafil citrate, sold under the name Viagra is the first of a new group of medication which allows adequate sexual stimulation, relaxes the blood vessels of the penis and helps erection. Sildenafil tablet should be taken once a day. The time necessary for Sildenafil to exercise its action is about half an hour. The effect is maintained for about four hours.
The effect is only obtained with a satisfactory sexual stimulation. » More info

Tadalafil, sold under the name of Cialis is a new group of medication which allows adequate sexual stimulation, relaxes the blood vessels of the penis and helps erection. The recommended dose of Tadalafil is 20mg.
Cialis is the only drug which is not only fast acting (works in 30 minutes) but is also know to be effective for as long as 36 hours, thus enabling you to choose the moment that is just right for you as well as your partner. You can take Cialis in the morning and be ready for the right moment during that day, evening or even during the next day. Millions of men have benefited from Cialis as it works effectively in mild, moderate or severe erectile dysfunction. » More info

Vardenafil is used in the treatment of erectile dysfunction. It can assist men with this disorder in achieving and maintaining an erection during sexual activity. It is commonly marketed under the trade name Levitra.
Vardenafil is closely related in function to Cialis and Viagra: it increases the blood flow to the penis to achieve and maintain an erection. However, in the clinical studies that were conducted as part of the FDA approval process, Levitra was shown to take effect faster, and last longer than Viagra. Vardenafil is usually taken with or without food 60 minutes before sexual activity. » More info