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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The big turnoff: stymied by politics and viagra, sex research goes limp
From Psychology Today, 1/1/05 by Justin Clark

IN THE SUMMER of 2003, a group of conservative members of Congress forced an audit of publicly funded sex studies, questioning the value of research derived from Asian prostitutes in San Francisco or everyday sexual risk-taking.

No legislation actually materialized from Congress--an amendment in the House of Representatives was defeated by two votes.

But a few months later, the Boston University Sexuality and Research Treatment Program quietly shut its doors. The National Institute of Mental Health had withdrawn funding, effectively closing down the 20-year-old program and its research into human sexual arousal.

Across the country, sex researchers are more worried about death than sex--that is, the slow demise of their own field. In the past year, conservative groups have pressured federal agencies to look long and hard at their spending plans. In a time of war and budget deficits, "these particular [National Institutes of Health] grants are simply not a wise use of taxpayer money," says Republican congressman Jeff Flake of Arizona.

Even the mere threat of funding cuts has had subversive effects, researchers say. It has, for example, forced many sex researchers to turn to drug companies for sponsorship. And that, according to Lenore Tiefer, professor of psychiatry at New York University, is ruining the sex lives of many Americans.

Sex researchers' dependence on pharmaceutical money, she says, has translated into a popular view that any sexual problem can be treated with a pill. As a consequence, sex research is drowning under "a tidal wave of reductionism, wherein sex is pelvic vascular function," says Tiefer. Drugs like Viagra, Cialis and Levitra are now the mass panacea for a flagging sex drive.

The critical questions of how emotions influence sexual feelings are no longer asked, researchers complain. They also say that whether the motive is political or financial, sex research has been diverted far from its original mission--deepening our understanding of this critical aspect of human behavior in a way that benefits all of society.

Sweeping the psychological side of sex under the rug in favor of the mechanical will ultimately hinder our understanding of the human condition, says Geoffrey Miller, an evolutionary psychologist and author of The Mating Mind. "If scientific funding agencies took on the goal of happiness as their responsibility, they would put sex research at the heart of the behavioral sciences."

Miller cites his own studies on kissing--why long-term couples often kiss less as the years go by and why people find kissing enjoyable in the first place--as examples of "a dark continent of research" that some would say is of questionable value. Studying the benefits of kissing could help couples rejuvenate a marriage and reduce divorce rates, says Miller, "but it's less threatening and more profitable to study orgasms."

What do conservative congressmen and others find so threatening? Childhood and adolescent sexuality, for starters. Few people want to acknowledge that children have sexual feelings, says Ohio State University psychologist Terri Fisher, yet adult sexual problems may have their origins in childhood. The issue is so taboo, she notes, that "we don't know how child sexuality bears on adult sexuality because no one has ever done a longitudinal study."

Another threat may be the suggestion that some sexual behavior considered undesirable--like infidelity--has deep roots in human nature. Miller's studies suggest that women's mate preferences vary during the menstrual cycle: At the peak of fertility women prefer handsome and creative men, but when fertility is low, they value men of social status and earning power. In other words, he says, women's divergent interests may lead them to cheat on a partner.

Pedophilia and sexual trauma are two topics unlikely to draw research funds from drug conglomerates or organizations under scrutiny in the current political climate. And yet these societal menaces could be better understood through the study of sexual arousal, "which we're on the verge of understanding," observes Janet Hyde, head of the psychology department at the University of Wisconsin.

Not all the objections to sexual research come from the political right. Feminists worry that any research that shows most sexual behavior is hardwired could be used to revive notions of females as a weaker or more irrational sex.

Ultimately, understanding the emotional and relational roots of sexuality is in society's best interests. It will provide a more direct route to satisfying relationships than drugs can, says University of New Brunswick researcher Sandra Byers. "Sexual satisfaction isn't just the absence of a problem, any more than happiness is the absence of depression."

COPYRIGHT 2005 Sussex Publishers, Inc.
COPYRIGHT 2005 Gale Group

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