In the US, even though sildenafil is available only by prescription from a doctor, it was advertised directly to consumers on TV (famously being endorsed by former United States Senator Bob Dole and football star Pelé). Numerous sites on the Internet offer Viagra for sale after an “online consultation”, often a simple 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. Viagra is also informally known as “vitamin V”, “the blue pill”, or “blue diamond”, as well as various other nicknames.
In 2000, Viagra sales accounted for 92% of the global market for prescribed erectile dysfunction pills. By 2007, Viagra’s global share had plunged to about 50% due to several factors, including the entry of Cialis and Levitra, along with several counterfeits and clones, and reports of vision loss in people taking PDE5 inhibitors. In 2008, the FDA forced Pfizer to remove Viva Cruiser, an advergame for Viagra, from its website, after the game failed to disclose risk information about the drug.
In February 2007, it was announced that Boots, the UK pharmacy chain, would try over-the-counter sales of Viagra in stores in Manchester, England. Men between the ages of 30 and 65 would be eligible to buy four tablets after a consultation with a pharmacist. In 2017, the Medicines and Healthcare products Regulatory Agency enacted legislation that expanded this nationwide., allowing a particular branded formulation of Sildenafil, Viagra Connect (50 mg), to be sold over the counter and without a prescription throughout the UK from early 2018. While the sale remains subject to a consultation with a pharmacist, the other restrictions from the trial have been removed, allowing customers over the age of 18 to purchase an unlimited number of pills  The decision was made, in part, to reduce online sales of counterfeit and potentially dangerous erectile dysfunction treatments.
Pfizer’s patents on Viagra expired outside the US in 2012; in the US they were set to expire, but Pfizer settled litigation with each of Mylan and Teva which agreed that both companies could introduce generics in the US on 11 December 2017. In December 2017, Pfizer released its own generic version of Viagra.
As of 2018, the U.S. Food and Drug Administration has approved 15 drug manufacturers to market generic sildenafil in the United States. Seven of these companies are based in India. This is likely to lead to dramatic price reductions.
Counterfeit Viagra, despite generally being cheaper, can contain harmful substances or substances that affect how Viagra works, such as blue printer ink, amphetamines, metronidazole, boric acid, and rat poison.
Pfizer’s patent on sildenafil citrate expired in some member countries of the EU, Austria, Denmark, France, Germany, Ireland, Italy, The Netherlands, Spain, Sweden, the United Kingdom and Switzerland on 21 June 2013. A UK patent held by Pfizer on the use of PDE5 inhibitors (see below) as treatment of impotence was invalidated in 2000 because of obviousness; this decision was upheld on appeal in 2002.
There were 2,958,199 prescriptions for Sildenafil in 2016 in England, compared with 1,042,431 in 2006.
In 2018, Viagra Connect, a particular formulation of Sildenafil marketed by Pfizer, became available for sale without a prescription in the UK, in an attempt to widen availability and reduce demand for counterfeit products.
Sildenafil is available as a generic drug in the United States, labelled for pulmonary arterial hypertension. As of 2016 branded pills cost about 50 times more than generic ones. In the United States as of 2015 the branded 50 mg pill cost is between 25.17 and US$37.88.
In the United States, Pfizer received two patents for sildenafil: one for its indication to treat cardiovascular disease (marketed as Revatio) and another for its indication to treat erectile dysfunction (marketed as Viagra). The substance is the same under both trade names.
In 1992, Pfizer filed a patent covering the substance sildenafil and its use to treat cardiovascular diseases. This would be marketed as Revatio. The patent was published in 1993 and expired in 2012. The patent on Revatio (indicated for pulmonary arterial hypertension rather than erectile dysfunction) expired in late 2012. Generic versions of this low-dose form of sildenafil have been available in the U.S. from a number of manufacturers, including Greenstone, Mylan, and Watson, since early 2013. Health care providers may prescribe generic sildenafil for erectile dysfunction. However, the generic is not available in the same dosages as branded Viagra, so using dosages typically required for treating ED requires patients to take multiple pills.
In 1994, Pfizer filed a patent covering the use of sildenafil to treat erectile dysfunction. This would be marketed as Viagra. This patent was published in 2002 and will expire in 2019. Teva sued to have the latter patent invalidated, but Pfizer prevailed in an August 2011 federal district court case. An agreement with Pfizer allowed Teva to begin to provide the generic drug in December 2017.
On 8 November 2012, the Supreme Court of Canada ruled that Pfizer’s patent 2,163,446 on Viagra was invalid from the beginning because the company did not provide full disclosure in its application. The decision, Teva Canada Ltd. v. Pfizer Canada Inc., pointed to section 27(3)(b) of The Patent Act which requires that disclosure must include sufficient information “to enable any person skilled in the art or science to which it pertains” to produce it. It added further: “As a matter of policy and sound statutory interpretation, patentees cannot be allowed to ‘game’ the system in this way. This, in my view, is the key issue in this appeal.”
Teva Canada launched Novo-Sildenafil, a generic version of Viagra, on the day the Supreme Court of Canada released its decision. To remain competitive, Pfizer then reduced the price of Viagra in Canada. However, on 9 November 2012, Pfizer filed a motion for a re-hearing of the appeal in the Supreme Court of Canada, on the grounds that the court accidentally exceeded its jurisdiction by voiding the patent. Finally, on 22 April 2013, the Supreme Court of Canada invalidated Pfizer’s patent altogether.
Manufacture and sale of sildenafil citrate drugs known as “generic Viagra” is common in India, where Pfizer’s patent claim does not apply. Trade names include Kamagra (Ajanta Pharma), Silagra (Cipla), Edegra (Sun Pharmaceutical), Penegra (Zydus Cadila), Manly (Cooper Pharma) and Zenegra (Alkem Laboratories).
Manufacture and sale of sildenafil citrate drugs is common in China, where Pfizer’s patent claim is not widely enforced.
Sildenafil was reclassified in New Zealand in 2014 so it could be bought over the counter from a pharmacist. It is thought that this reduced sales over the Internet and was safer as men could be referred for medical advice if appropriate.
Egypt approved Viagra for sale in 2002, but soon afterwards allowed local companies to produce generic versions of the drug, citing the interests of poor people who would not be able to afford Pfizer’s price.
Pfizer’s patent on sildenafil citrate expired in Brazil in 2010.
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