Twenty years ago, an American pharmaceutical headquartered in New York city got the green light to sell a little blue pill that treats impotence.
Today, the diamond-shaped blue pill has transformed the sexual landscape.
Before Viagra, impotence meant shame and often the collapse of all but the most committed relationships.
With a Google search, which throws up more than 10 million references, it is easy to see how Viagra has become the world’s most ubiquitous medical brand name.
The discovery of its startling ability to restore men's faded sexual function triggered a social revolution as monumental as that caused by the contraceptive pill.
Initially, Viagra was developed to treat high-blood pressure and chest pain, but quickly showed an unexpected side-effect during clinical trials: combating erectile dysfunction— celebrated as a real revolution for men, transforming the relationships of millions over the past two decades.
Today marks Viagra's 20th anniversary since approval by the US’ Food and Drugs Administration.
At the start of the 1990s, teams at Pfizer experimented with a new drug called Sildenafil used to treat chest infections.
30 million men
Although the drug proved powerless in calming thoracic pain, it had an unexpected side-effect on men: it caused an erection.
The majority of the male volunteers in the experiments that followed also reported a significantly improved sex life, compelling Pfizer to change tack to instead focus on researching male impotence, a problem that affects a third of men over 40.
With billions of pills sold, the drug unleashed a cultural shift across the globe and made sex possible again for millions of older men.
In the two decades since Viagra first went on sale, more than 30 million men in 120 countries have used it.
In addition, many millions more have bought it illegally on the internet, or taken a few from their mates in bars, for recreational use.
Indeed, the take-off of Viagra was one of the fastest that a new drug has ever seen.
Almost immediately after its launch in America, it was being prescribed at the rate of at least 10,000 a day.
But has the 'wonder pill' really lived up to its promise? Has it been a universal force for good?
From the financial perspective there can be little doubt.
From a relationship perspective, it has brought joy to many.
But it has also had, in many cases, a destructive impact, becoming the third party in many marriage splits.
The widespread availability of Viagra has posed its own problems, not just for patients suffering circulation problems but for men of all ages who use it as a recreational drug.
“Viagra is spawning a nation of men who are dependent on the drug, particularly young men who develop the expectation that they should be able to just pop a pill and have sex, regardless of how they feel emotionally,” said fertility expert Jane Machira.
Although no other drug has proven to be as effective as Viagra, the company behind the drug, Pfizer, is wrestling with declining sales.
Global sales were at Ksh121 billion ($1.2 billion) in 2017, down by nearly half of Ksh211 billion ($2.1 billion) five years earlier.
The giant pharmaceutical has also had to fight the proliferation of fake drugs.
A 2011 poll conducted by the pharma showed 80 per cent of Viagra randomly bought online is fake.
The unlicensed versions can contain toxic products such as pesticides, plaster or ink for printers.
And as fake versions of the drug spread, so too do alternative uses, with a British study in 1999 showing a small but significant use of the pill among young partygoers.
The drug is also experimented with in sports doping.
However the World Anti-Doping Agency (WADA) decides not to add Viagra to its list of banned substances: Sildenafil, it concludes, only has doping effects in high altitude.
But how did a drug that was originally tested for the treatment of heart problems end up in bedrooms across the world? Take a look back at Viagra's history.
• 1989: British Pfizer scientists Peter Dunn and Albert Wood create a drug called sildenafil citrate that they believe will be useful in treating high-blood pressure and angina, a chest pain associated with coronary heart disease. The drug is classified as UK-92480.
• 1991: Dr. Nicholas Terrett is named in the British patent for sildenafil citrate, or Viagra, as a heart medication. Terrett is often considered the father of Viagra, according to ViagraBox.com.
• Early 1990s: Pfizer completes several early trials of sildenafil citrate that provides little hope for its use as a heart disease treatment. But volunteers in the clinical trials report increased erections several days after taking a dose of the drug, according to researcher Ian Osterloh.
"Around the same time, other studies were revealing more information about the biochemical pathway involved in the erection process," he writes for Cosmos magazine.
"This helped us understand how the drug might amplify the effects of sexual stimulation in opening up the blood vessels in the penis. With UK-92480′s chances of treating angina now slim, we decided to run pilot studies in patients with erectile dysfunction."
• 1996: Pfizer patents sildenafil citrate in the United States.
• March 1998: The FDA approves the use of the drug Viagra to treat erectile dysfunction. In the following weeks, experts estimate, US pharmacists dispense more than 40,000 Viagra prescriptions.
• May 1998: TIME magazine's cover story, "The Potency Pill" quotes Penthouse publisher Bob Guccione as saying he believes Viagra will "free the American male libido" from the emasculating doings of feminists. Feminists are not amused.
• On CNN's Larry King Live show, former presidential nominee Bob Dole admits he took part in experimental trials for Viagra, calling it "a great drug."
• June 1998: Newsweek calls Viagra the "hottest new drug in history almost everywhere in the world." At the time Viagra is only legal in the United States, Brazil, Morocco and Mexico, but Newsweek reports growing black market sales in other countries.
• December 1998: Pfizer announces it has hired Bob Dole for a television campaign aimed at raising awareness of male impotence.
• The Washington Post reports that the CIA is using Viagra to gain friends in Afghanistan. "While the CIA has a long history of buying information with cash, the growing Taliban insurgency has prompted the use of novel incentives and creative bargaining to gain support in some of the country's roughest neighborhoods, according to officials directly involved in such operations."
• July 25, 1999: Popular TV show "Sex and the City" airs "The Man, The Myth, The Viagra," in which character Samantha dates a wealthy older man who uses the little blue pills. In the next season, Samantha takes the little blue pill herself to enhance her sexual experiences.
• 2000: Dr Sanjay Kaul presents research at the 49th Annual Scientific Session of the American College of Cardiology that suggests 522 patients died while taking Viagra in the first year the drug was on the market.
• August 19, 2003: The FDA approves Bayer Corporation's vardenafil hydrochloride, sold under the brand name Levitra, to treat erectile dysfunction in men.
• November 21, 2003: The FDA approves pharmaceutical company Lilly USA's tadalafil, or Cialis, for the treatment of erectile dysfunction. The side effects for Cialis are similar to Viagra, and men with heart problems or abnormal blood pressure are advised against taking it.
• 2006: Rush Limbaugh is detained at a Florida airport after a bottle of Viagra is found in his luggage. The name on the prescription bottle does not match his. Limbaugh's attorney says his doctor had prescribed the Viagra under a different name "for privacy purposes," according to Forbes.
• 2010: Actor Michael Douglas makes headlines when he admits to AARP magazine that he has used erectile dysfunction drugs with wife, actress Catherine Zeta-Jones.
"Bless her that she likes older guys," he says. "Some wonderful enhancements have happened in the last few years—Viagra, Cialis— that can make us all feel younger."
• 2011: A federal judge extends Pfizer's US patent for Viagra, making sure generic brands cannot come to market until 2019, according to the Wall Street Journal.
• April 2012: The FDA approves a new erectile dysfunction drug called avanafil, which was to be sold under the brand name Stendra.
Stendra is taken on an as-needed basis 30 minutes before sexual activity, according to a news release.
German court rules insurers don't have to pay for Viagra.
• 2013: Generic forms of Viagra are made available in Europe and in the US from late 2017.
Other uses for Viagra
• Heart attacks
Researchers at Virginia Commonwealth University in the US found that Viagra administered to patients after a heart attack stopped a condition where heart muscle cells kill themselves in the wake of a heart attack (apoptosis) and helped to restore blood flow and tissue healing.
• Pulmonary arterial hypertension
Few patients of this condition survive beyond three to four years.
A Viagra-based drug, sildenafil, under the trade name Revatio, extends the lives of some sufferers by boosting blood flow to the lungs, reducing the workload on the heart.
A condition marked by high blood pressure and headaches.
In 2005, a University of Vermont College of Medicine team in the United States found Viagra prevented deaths among foetuses in pregnant rats by relaxing muscles in the artery walls allowing adequate blood flow.
Viagra could increase a woman's chances of becoming pregnant, where the cause of infertility is the lining of the uterus being too thin to sustain a pregnancy.
Tests show the drug increases blood flow to the uterus and stimulates the growth of cells.
Sources: AFP, The Guardian, CNN, Pfizer, scientific publications from the British Medical Journal and Journal of Sexual Medicine.