History of Viagra

Viagra, with its active ingredient-Sildenafil citrate, is a medication meant to treat erectile dysfunction in men. This drug was created by Pfizer, the pharmaceutical company. Viagra works by inhibiting the cGMP phosphodiesterase type 5 enzyme, which regulates the penis’ blood flow. Sildenafil citrate has been on the market since 1998. Its main competitors are Vardenafil (Levitra) and Tadalafil (Cialis).

Compound UK-92, 480 (Sildenafil citrate) was elaborated by pharmaceutical chemists in the research facility of Pfizer, in England. This compound was first being study for its application in hypertension and angina pectoris. Viagra’s first clinical trials took place in Morriston Hospital, in Swansea. During the phase I of the clinical trial, under Ian Osterloh, data showed that Sildenafil citrate did not improve the symptoms of angina pectoris, but, that it did cause remarkable penile erections. Viagra was patented in 1996, and it was approved for the treatment of erectile dysfunction by the United States Food and Drug Administration on March, 1998. It became the first treatment to be approved to medicate erectile dysfunction in the United States. Afterwards, Viagra’s sales even reached one billion US dollars by 2001.

In the year 2000, Viagra had over 90 percent of the global market sales for pills being prescribed to treat erectile dysfunction. By the year 2007, Viagra’s market share had been reduced to 50 percent, because of the emergence of competitors, such as, Levitra and Cialis.

The patent for Sildenafil citrate, by Pfizer, will expire in the 2011-2013 period. But, the patent is not worldwide as it was nullified in the United Kingdom for the treatment of male impotence.

Viagra is easy to obtain since various websites have it for sale, in which, patients only have to complete an online consultation, consisting of a basic online questionnaire without having to undergo a doctor’s physical examination. Viagra is only available by prescription in most countries. The global market is now flooded with many aphrodisiacs that are called “Natural Viagra,” in order to cash-in the famous brand name. Also, Viagra’s nicknames include, “the blue pill” and “vitamin V.”

How Viagra Operates

Sildenafil citrate works by releasing nitric oxide into the corpus cavernosum portion of the penis. Then, the nitric oxide attaches to the receptors of the enzyme called guanylate cyclase which causes an increment in the levels of the cyclic guanosine monophosphate (cGMP). The cyclic guanosine monophosphate causes the relaxation of muscle by vasodilatation of the intimae section of the helicine arteries, therefore, creating a higher influx of blood into the penis which causes the resulting erection.

Sildenafil citrate’s molecular structure is compatible with cGMP, acting as a competitor binding agent of the cGMP specific phosphodiesterase type 5 (PDE5) in the corpus cavernous of the penis, which results in higher concentrations of cGMP and more durable erections. Sildenafil does not usually cause an erection without sexual stimulation, because it is necessary to activate the NO/cGMP combo. Vardenafil (Levitra) and Tadalafil (Cialis) have a similar function.

Also, liver enzymes metabolize Viagra in the organism. Viagra is then excreted by the kidneys and the liver. If Sildenafil citrate is taken with foods that contain high quantities of fatty acids, its absorption is reduced. The highest plasma concentration of Viagra is then reached approximately after one hour of ingestion, if combined with this kind of greasy foods.