What is Viagra?
Viagra is the trade name for a drug called Sildenafil. Viagra is one of a class of drugs known as PDE-5 (Phosphodiesterase type 5) inhibitors. Viagra and the other PDE-5 inhibitors can help men with erectile dysfunction (male impotence) by enhancing the erectile response when a man is sexually stimulated. Aside from Viagra, the other drugs in this class are Cialis (Tadalafil) and Levitra (Vardenafil).
How does Viagra work?
Viagra does not cause a man to be sexually aroused. Viagra is only effective if you are sexually aroused. To understand how it works you need to understand the mechanics of how a man gets an erection. When you get sexually stimulated, the nervous system in the erectile tissue of your penis releases nitric oxide (NO). The nitric oxide stimulates an enzyme that produces something called a messenger cyclic guanosine monophosphate (cGMP). The cGMP relaxes the smooth muscle cells. One result of this is that the arteries in your penis dilate and the blood can flow into your penis more easily. Another result is that the erectile tissue itself fills with blood. Both of these process result in an erection. Viagra works by maintaining the level of cGMP in the smooth muscle cells. If you are not turned on, your brain will not stimulate the release of any nitric oxide and you will not produce any cGMP.