Viagra (Sildenafil Citrate)
Viagra Information
Viagra is a brand name the Pfizer company gave to a chemical called sildenafil citrate. It is prescribed as a medication to treat erectile dysfunction.
Erectile dysfunction is the inability to have or maintain an erect penis for satisfactory sexual performance. It is also referred to as male impotence.
In the late 1980's and 1990's, Pfizer was doing research on a chemical with the code name UK-92480. At that time 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 initially hoped it would.
However, some of the men who were taking part in the tests reported that for several hours after consuming sildenafil citrate, they got an erection when sexually stimulated.
Even more important was the fact that men who had previously been diagnosed as impotent were getting the same results as men who had no history of erectile dysfunction.
Pfizer decided to test sildenafil citrate for treating impotence 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.
How Does Viagra Work
Medications like viagra, cialis, and 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.
Does Viagra Work For Every Man Men with psychological impotence (erectile dysfunction caused by mental factors like stress, fatigue, anxiety, depression) respond very well to viagra, cialis, and levitra.
As long as there are no underlying physical reasons that are causing problems. Viagra, cialis, and levitra work for about 90% of men with psychological erectile dysfunction.
There are various physical reasons for erectile dysfunction, but one of the most common reasons (especially in men over forty years of age) is that arteries in part of the penis are not relaxing enough to allow more 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 30-60 minutes, enough PDE5 inhibitor will be available to the penis to cause an erection when the penis is stimulated by touch.
In a small minority of men, just thinking about or seeing something sexually stimulating is enough to cause an erection. But for most, some kind of physical stimulation of the penis is required.
Viagra will not work for every man with erectile dysfunction, but medical tests and reports from actual viagra consumers confirm that it works for about 70%-80% of the men with physical reasons for erectile dysfunction.
Some failure cases are from men that have had some form of surgery that made getting or maintaining an erection physically impossible. For example, men who have had penile implants may have muscle scarring that will cause viagra to be ineffective.
Although there is no upper age limit for viagra, elderly men (particularly those with severe vascular disease) may not see much improvement.
Viagra Dose For men that have decided they would like to be treated with this medication, consult your physician before trying it.
The most commonly prescribed viagra dose size is 50 milligrams taken 30-60 minutes before sexual activity. The first time you take viagra a 50 milligram dose is recommended unless your doctor tells you otherwise.
If it does not produce the results you had hoped for you can try a 100 milligram dose on subsequent attempts. However, the dose you take should never exceed 100 milligrams and you should never ingest more than one dose per 24 hour period.
Your doctor may want you to limit your intake to a 25 milligram dose if you are over age 65, or have serious kidney or liver problems. Never take generic viagra within 24 hours of ingesting other erectile dysfunction meds like cialis or levitra.
The only product the works exactly the same as viagra is generic viagra. Beware of products sold with viagra in their name, to make them appear to be similar to, or affiliated with, real viagra. Things like natural viagra, and other similar substances should be avoided.
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last update: january 2011