Sildenafil chemical structure
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Viagra

Sildenafil citrate, sold under the names Viagra, Revatio and (in the Indian subcontinent) Caverta, is a drug used to treat male erectile dysfunction (impotence) and pulmonary arterial hypertension (PAH), developed by the pharmaceutical company Pfizer. Viagra pills, intended to treat impotence, are blue with the words "Pfizer" on one side and "VGR xx" (with xx representing 25, 50 or 100, the dose of that pill in milligrams) on the other. more...

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History

Sildenafil, initially known as compound UK-92,480, was initially developed to treat angina pectoris (a form of cardiovascular disease). Phase I clinical trials suggested that the drug had little effect on angina, but that it could induce marked penile erections. Pfizer therefore decided to market it for erectile dysfunction, rather than for angina. The drug was patented in 1996, approved for use in erectile dysfunction by the FDA on March 27, 1998, becoming the first pill approved to treat erectile dysfunction in the United States, and offered for sale in the United States later that year. It soon became a great success: annual sales of Viagra in the period 1999–2001 exceeded $1 billion.

The name "Viagra", like many drug names, is a marketing invention. It was possibly inspired by the Sanskrit word "vyāghra", which means "tiger". The word rhymes with "Niagara" (Niagara Falls is a popular honeymoon destination and Niagara, being such an impressive cataract, evokes a sense of incredible erectile and ejaculatory strength). The sound of the word also suggests the words "vigor" and "virile".

Even though Viagra is only available by prescription from a doctor, it was advertised directly to consumers on TV (famously being endorsed by Bob Dole). Numerous sites on the Internet offer Viagra for sale after an "online consultation," a mere web questionnaire. The "Viagra" name has become so well known that many fake aphrodisiacs now call themselves "herbal Viagra" or are presented as blue tablets imitating the shape and colour of Pfizer's product. A mixture of Viagra and ecstasy, called sextasy, has become popular among rave partygoers. Viagra is also informally known as "Vitamin V", "the Blue Pill", and goes by various other nicknames.

It has been suggested that Viagra would lead to a marked drop in the demand for certain traditional remedies, such as tiger penises and rhinoceros horns and that the drug may therefore help to preserve these endangered species. However, this is unlikely in that these parts of endangered species are not only used to treat impotence. Rhinoceros horns, for example, are used as a treatment for high fever. Furthermore, since Viagra has not been shown to possess aphrodisiac properties, it is unclear that the natural remedies would compete with this new clinical drug.

Pfizer's worldwide patents on sildenafil citrate will expire in 2011–2013. The UK patent held by Pfizer on the use of PDE5 inhibitors (see below) as treatment of impotence has been invalidated in 2000 because of obviousness; this decision was upheld on appeal in 2002.

Mechanism of action

Part of the physiological process of erection involves the parasympathetic nervous sytem to release nitric oxide (NO) in the corpus cavernosum of the penis. NO binds to the receptors of the enzyme guanylate cyclase which results in increased levels of cyclic guanosine monophosphate (cGMP), leading to smooth muscle relaxation (vasodilation) in the corpus cavernosum, resulting in increased inflow of blood and an erection.

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Party hard: with Viagra and its coitus-enabling cousins so easy to score, throngs of young, impotence-free guys are popping pills to become wayward weekend
From Men's Fitness, 11/1/04 by Jonathan Yevin

"A FEW YEARS AGO, I GOT offered a Viagra at a party" says Mike Rodriguez, 26, recalling the first time he took the blue pill. "I was with this girl I met the week before and I was pretty, sure I could take her home. I popped the pill a half-hour before we left the party. We had sex until she literally made me stop."

Rodriguez, a network engineer from New York City, had never suffered from impotence or performance anxiety. Yet he was using Viagra anyway, in this case as an insurance policy against the effects of alcohol.

Xavier Motley, a 27-year-old soldier from Pennsylvania, buys Viagra from an online pharmacy in Mexico. "I take it to enhance my endurance," says Motley, who has never had performance issues, either.

Viagra and its newer rivals, Levitra and Cialis, are erectile-dysfunction drugs, which were developed and intended for old salts who had trouble hoisting their sails. But in the last few years, these pharmaceuticals have caught on as recreational drugs with the under-30 crowd.

A new study published in the International Journal of Impotence Research (yes, it's a real publication) found that, while the largest group of Viagra users are still in the 56-and-older age group, there's been a 300% increase in prescriptions for men under 45 since the drug was launched in 1998. Add to that the untold thousands who buy it online, and it's clear that the country is in for some hard times.

But there's a dark side to this invisible helping hand. The consequences of large numbers of men taking potency pills they don't need are raising eyebrows in the medical community. For one thing, Viagra works for four to six hours, which, when combined with alcohol, can open the door wider to making unwise late-night choices. "Alcohol promotes uninhibited behavior," notes Andrew McCullough, M.D., a Manhattan urologist. "All of a sudden, an inebriated guy might decide, 'I'm not gonna wear a condom tonight.'"

The same goes for men who get all revved up and have no place to go. Desperately searching for release with any matter of partner can also lead to less-than-smart lifestyle decisions. "If I'm out and I pop a pill and I can't get sex," admits Rodriguez, "I usually call an escort service."

These pharmaceuticals are creating another potential set of dilemmas. Scientists have found that, while men don't develop physical dependencies on the drugs or loss of normal function if they stop taking them after extended use, psychological dependence is a different matter altogether. The recreational user might take Viagra to help sell himself as a sexual superman early in a relationship. But once things get serious, he has to perform without the support of his little diamond-shaped friend.

Says Motley, "I worry that not taking it will cause my girlfriends to notice a drop-off in my performance."

All erectile-dysfunction drugs work in the same way. Each blocks an enzyme called phosphodiesterase-5, relaxing smooth-muscle cells to allow increased blood flow to the penis. (All three also have similar possible side effects, the must common being headaches and facial flushing.)

Each of the three drugs has also targeted the same demographic: younger men. Though Viagra is still far and away the industry leader, Cialis and Levitra have made serious inroads in market share, especially in Europe. So tar, Viagra has been prescribed 170 million times to 23 million men worldwide. Since Cialis and Levitra were launched last year, they have claimed 24% and 12%, respectively, of the European marketplace, compared with Viagra's 64%. In France, Cialis has been dubbed "Le Weekender,' as it stays potent for up to 36 hours. Cool. But imagine the problems posed by an almost two-day stiffy.

"I saw a 22-year-old with a prolonged erection," says McCullough. "I saw another with a penile fracture. He had had rodeo sex. She came down on him and it broke" Ouch.

Buckin' broncos aside, there are many young males who have legitimate erectile dysfunction. For them, Viagra and the other drugs may mean the difference between knocking down three pointers from the top of the key and warming the bench. But other than for reproductive sex, what is Viagra for if not recreational use?

"The problem in our society is, if good is good, why not be better than good?" says McCullough. "We haven't studied the effect in men without erectile dysfunction--there may be consequences. Enhancing sex for the sake of enhancing sex should not be condoned."

Jonathan Yevin, a Brooklyn-based writer and photographer, knows every Viagra joke in the book.

COPYRIGHT 2004 Weider Publications
COPYRIGHT 2004 Gale Group

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