Viagra is a brand name the Pfizer company chose for a chemical with the generic name sildenafil citrate. It is prescribed as a medication to treat erectile dysfunction.
Erectile dysfunction is the inability to have or maintain an erect penis long enough for satisfactory sexual performance. This is something almost every man will face at some time in their life.
In the late 1980s and 1990s, Pfizer was doing research with a chemical they called UK-92480. It was being investigated as a treatment for angina and high blood pressure.
During clinical trials it was noticed that the drug did not help angina and high blood pressure sufferers as much as was hoped it would.
However, some of the men who were taking part in the tests reported that after consuming sildenafil citrate, they got an erection when their member was stimulated by touch.
Even more important was the fact that men who had previously been diagnosed with erectile dysfunction were getting the same results as men who had no history of erectile dysfunction.
Pfizer decided on performing medical trials with sildenafil citrate as a treatment for erectile dysfunction, with some very impressive results.
Viagra was then patented in 1996, and in 1998 it was approved by the FDA as the first oral medication to treat erectile dysfunction.
It should be noted that Pfizer also markets sildenafil citrate as a treatment for pulmonary arterial hypertension. Medication for this purpose is marketed under the brand name revatio.
Medications like viagra, cialis, or levitra work by inhibiting a chemical called phosphodiesterase type 5. Because of their mode of action, these drugs are commonly referred to simply as PDE5 inhibitors.
When a man gets sexually excited, it triggers cells in the penis to produce nitric oxide. The increase in nitric oxide will in turn cause production of cyclic guanosine monophosphate (cGMP).
The cGMP causes arteries in part of the penis to relax and allow more blood to flow through them. The increase in blood flow causes an erection.
If the enzyme phosphodiesterase type 5 (PDE5) is of sufficient quantity, it will attack the cGMP and erection will not be maintained.
Viagra and other PDE5 inhibitors reduce the amount of PDE5 available to attack cGMP. With a reduction of PDE5, a majority of men are able to maintain an erection to orgasm.
Although viagra is not intended for the very young, sildenafil may be employed to treat children with pulmonary arterial hypertension. When this is the case, sildenafil marketed as revatio is prescribed.
Men with psychological erectile dysfunction (caused by mental factors like stress, fatigue, anxiety, depression) respond very well to viagra, as well as similar medications like cialis and levitra.
As long as there are no fundamental physical reasons that are causing problems, products like viagra, cialis, levitra, work for about 90% of men with psychological erectile dysfunction.
One of the most common physical reasons for erectile dysfunction is that arteries in part of the penis are not allowing adequate amounts of blood to flow through them.
Even when sexually aroused, the amount of PDE5 is too large. The quantity of cGMP produced is overwhelmed, and an erection can not be developed or maintained long enough for satisfactory sexual performance.
When a man takes viagra on an empty stomach, in about 60 minutes, enough PDE5 inhibitor will be available to the penis to cause an erection when the penis is stimulated by touch.
Viagra will not work for every man with erectile dysfunction, but medical tests and reports from actual viagra consumers indicate that it works for about 70%-80% of the men with physical reasons for erectile dysfunction.
If you are considering taking viagra for the first time, there are certain things a person should be aware of. See the precautions page to better inform yourself.
In the US, the patent for viagra as treatment of erectile dysfunction will expire in 2019. At that time, generic viagra will become legally available in American pharmacies.
Beware of misleading products with viagra in their name. Things like uncle fester brand herbal viagra, hardwood natural viagra, or other similar substances should be avoided.