Ten years ago this month the lives of millions of men and women were changed almost overnight by the advent of a little blue pill -- the first oral treatment for impotence.
Viagra, developed by accident by scientists at Pfizer Laboratories, was first approved for use by the US Food and Drug Administration on March 27, 1998.
"Originally, we were testing sildenafil, the active drug in Viagra, as a cardiovascular drug and for its ability to lower blood pressure," said Dr Brian Klee, senior medical director at Pfizer.
"But one thing that was found during those trials is that people didn't want to give the medication back because of the side effect of having erections that were harder, firmer and lasted longer."
Since Viagra went on the market it has been used by 35 million men around the globe, and it took impotence off the taboo list, making it infinitely easier to treat.
Urologists' waiting rooms became busier as news got round that the condition, which was rechristened with a new, scientific name -- erectile dysfunction, or ED -- could be treated with a triangular blue pill.
Previous treatments had involved surgically inserting a prosthesis into the penis, injecting a substance into the male sex organ or using urethral suppositories.
"Viagra brought a lot more people into the office because of the ease of treatment," Dr Irwin Shuman, a urologist of 40 years' experience in Washington, told AFP.
"In the old days, when we didn't have much in the way of treatment, we would do a lot more evaluation, looking for answers as to why somebody had the problem," he said.
In one test, men would be observed while sleeping to see if erections occurred.
Men who failed to get the usual five to six erections per night were deemed to have a physical problem, and those who did get nocturnal erections were said to have a psychological problem and were sent to see a sex counsellor.
So Viagra helped move impotence out of the psychological realm and into the world of physical illnesses. "What we have come to understand in the past 10 years is that ED is a vascular disease," said Klee.
"What happens is veins and arteries that deliver and remove blood from the penis are not working the way they should, and Viagra allows those vessels to dilate and increase blood flow to the penis," he said.
Dr Abraham Morgentaler, director of Men's Health Boston, and associate clinical professor of urology at Harvard Medical School, hailed Viagra as a "benefit to medicine."
But, he added, the drug has not delighted all those who took it.
"There are two truths to Viagra: for those who refill (get a new prescription), it's wonderful and they're happy," Morgentaler told AFP.
"But a lot of people look to Viagra for personal happiness, thinking a hard penis can resolve relationship issues," and they end up disappointed, added the doctor and author of the book "The Viagra Myth."
Some patients say taking Viagra "does not correspond to the way they want to have sex," Morgentaler said.
Viagra works best on an empty stomach or after eating a low-fat meal, the medication's official website says. It kicks in about 30 minutes after being taken, works for four hours, and only with sexual arousal, the website says.
But it's not the answer for everyone. Morgentaler said he had a 78-year-old patient in his office who "didn't like the idea of programming sex. Guys, and often women, too, don't necessarily want to compromise the ideal of sex as something magical, spontaneous, romantic."
Morgentaler also spoke of the darker side of Viagra, which has evolved since it and two other ED treatments became easily available over the Internet.
"It's the use of Viagra by healthy young men who don't need it," he said.
"These young men take a pill whenever they go out ... Maybe because they are inexperienced or shy and Viagra makes them more confident, or maybe because they have inflated ideas about what sex is supposed to be like from seeing Internet porn, which they also have easy access to, and they want to heighten their feelings of masculinity," he said.
"I am concerned -- not that these young men will get addicted physically, but that they will become psychologically dependent on Viagra," said Morgentaler.
"Sex is an entree into a relationship, and most often what we want from a relationship is to be loved for what we are.
"But some of these young men feel they have to take a pill to be acceptable, and I fear they are potentially missing the opportunity to have true emotional connections with a partner, based on reality, not mythology."