The following contains excerpts from Wikipedia; About.com (Mary Bellis) and Milestones in Drug Therapy – Sildenafil, by Michael J. Parnham, Jacques Bruinvels and other contributors, 2004, also found at www.coreynahman.com.

Although the British press portrayed Pfizer employees Peter Dunn and Albert Wood as the inventors of sildenafil, now known as Viagra, they are generally accepted as the duo who synthesized the drug in 1989, along with other Pfizer co-workers at the company’s Sandwich, Kent research facility in England.

The names of Andrew Bell, Dr. David Brown and Dr. Nicholas Terrett (also Pfizer employees at the same English research facility) are important to the history of Viagra because they originally helped discover that chemical compounds belonging to the pyrazolopyrimidinone class were useful in treating heart problems such as angina.

Terrett was named in the 1991 British patent for sildenafil as a heart medicine, and some experts consider him as the father of Viagra. Terrett maintains that his team discovered how useful the drug might be, but that Dunn and Wood actually synthesized the drug in 1989, bringing all of the components of Viagra together into one pill/dosage.

Dunn and Wood do appear on the manufacturing patent application for sildenafil citrate, although Pfizer states that numerous employees contributed to the discovery of compound UK-92,480/sildenafil/sildenafil citrate/Viagra.

Viagra was initially studied for use in hypertension (high blood pressure) and angina pectoris (a symptom of ischaemic heart disease). Phase I clinical trials under the direction of Ian Osterloh suggested that the drug had little effect on angina, but that it could induce marked penile erections.

After Phase II testing of sildenafil for angina failed to show promising results, Pfizer decided to pursue its use for erectile dysfunction rather than for angina. The drug was patented in 1996 and approved for use in erectile dysfunction by the U.S. Food and Drug Administration on March 27, 1998. Viagra became the first oral treatment approved to treat erectile dysfunction in the United States, and it was offered for sale in the United States later that year. Sales of Viagra continue to exceed well over $1 billion per year.

Dr. Simon Campbell, who was the Senior Vice President of Medicinal Discovery at Pfizer and oversaw Viagra's development, was also a key player in the discovery of Viagra. He retired from Pfizer in 1998 and according to a Pfizer press release on June 8 of that year, Campbell was “a key member of the Pfizer teams that discovered three of the company's important new medicines (including)… Viagra, the first oral medication for erectile dysfunction…”

Even though sildenafil is available only by prescription from a doctor, many have argued that Viagra has been marketed by Pfizer as a recreational drug.

Many famous celebrities and politicians have appeared in TV, radio and print ads to help sell the product, including former United States Senator Bob Dole and soccer star Pelé, in Latin America and Europe. Political analyst Rush Limbaugh, former baseball player Rafael Palmeiro and former NASCAR driver Mark Martin have also served as spokesmen.

Online pharmacies now provide Viagra after an online consultation with a doctor, which typically involves an online health/medical questionnaire.

The Viagra name has grown to be so popular since 1998 that countless companies, many not located in the United States, illegally manufacture and sell products such as "herbal Viagra," “professional Viagra” or “generic Viagra.” Pfizer has not granted the permission for these companies to use the Viagra name or to sell these non-FDA approved drugs that bear Viagra’s name. These non-genuine, counterfeit versions of Viagra, although usually cheaper, contain unknown ingredients that produce unknown results, and are thereby considered a health risk.

In 2000, Viagra sales accounted for 92 percent of the global market for prescribed erectile dysfunction pills. By 2007, Viagra's global share had plunged to about 50 percent due to several factors, including the 2003 market introductions of FDA-approved Cialis and Levitra, along with several other counterfeits and clones. Pfizer's worldwide patents on sildenafil citrate will expire between 2011 and 2013.

• 5250534 expires March 27, 2012
• 6469012 (patent use code U-155; Treatment of Erectile Dysfunction) expires Oct. 22, 2019

From http://inventors.about.com/od/uvstartinventions/a/Viagra.htm

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