Editing Sildenafil (section)

===Regional issues===

====United States====
In 1992, Pfizer filed a patent covering the substance sildenafil and its use to treat cardiovascular diseases.<ref>{{US patent|5250534}}</ref> 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 drug|Generic versions]] of this low-dose form of sildenafil have been available in the US from a number of manufacturers, including Greenstone, Mylan, and Watson, since early 2013.<ref>{{cite news |url=http://www.zacks.com/stock/news/86972/Pfizers-Revatio-Goes-Generic |title=Pfizer's Revatio Goes Generic |date=15 November 2012 |publisher=Zacks Equity Research |access-date=5 October 2013 |archive-date=12 October 2013 |archive-url=https://web.archive.org/web/20131012062327/http://www.zacks.com/stock/news/86972/Pfizers-Revatio-Goes-Generic |url-status=live }}</ref> Health care providers may prescribe generic sildenafil for erectile dysfunction.<ref name="Skinner March 2016"/> For a time, the generic was not available in the same dosages as branded Viagra, so using dosages typically required for treating ED required patients to take multiple pills.<ref name="Skinner March 2016"/>

In 1994, Pfizer filed a patent covering the use of sildenafil to treat erectile dysfunction.<ref>{{US patent|6469012}}</ref> This would be marketed as Viagra. This patent was published in 2002 and expired in 2019. [[Teva Pharmaceutical Industries|Teva]] sued to have the latter patent invalidated, but Pfizer prevailed in an August 2011 federal district court case.<ref>{{cite news |url=https://www.bloomberg.com/news/2011-08-15/pfizer-wins-viagra-patent-infringement-case-against-teva-pharmaceuticals.html |title=Pfizer Wins Viagra Patent Infringement Case Against Teva Pharmaceuticals |date=15 August 2011 |publisher=Bloomberg |access-date=1 April 2012 |vauthors=Milford P |archive-date=11 January 2015 |archive-url=https://web.archive.org/web/20150111001411/http://www.bloomberg.com/news/2011-08-15/pfizer-wins-viagra-patent-infringement-case-against-teva-pharmaceuticals.html |url-status=live }}</ref> An agreement with Pfizer allowed Teva to begin to provide the generic drug in December 2017.<ref name="Skinner March 2016"/>

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 brand names.<ref name="Skinner March 2016"/>

Sildenafil is available as a generic drug in the United States, labeled for pulmonary arterial hypertension,<ref name="Skinner March 2016">{{cite web|vauthors=Skinner G|title=Yes, There Is a Way to Get Generic Viagra|url=http://www.consumerreports.org/drugs/yes-there-is-a-way-to-get-generic-viagra/|website=Consumer Reports|access-date=4 May 2016|date=4 March 2016|archive-date=2 May 2016|archive-url=https://web.archive.org/web/20160502201031/http://www.consumerreports.org/drugs/yes-there-is-a-way-to-get-generic-viagra/|url-status=live}}</ref> and to treat erectile dysfunction, as the patent expired in April 2020.<ref name=Pfizer/>

In the US, Revatio and Viagra are marketed by [[Viatris]] after Upjohn was spun off from Pfizer.<ref>{{cite web | title=Pfizer Completes Transaction to Combine Its Upjohn Business with Mylan | publisher=Pfizer | via=Business Wire | date=16 November 2020 | url=https://www.businesswire.com/news/home/20201116005378/en/ | access-date=17 June 2024}}</ref><ref>{{cite web | title=Revatio | website=Pfizer | url=https://www.pfizer.com/products/product-detail/revatio | access-date=17 June 2024 | archive-date=17 June 2024 | archive-url=https://web.archive.org/web/20240617051424/https://www.pfizer.com/products/product-detail/revatio | url-status=live }}</ref><ref>{{cite web | title=Viagra | website=Pfizer | url=https://www.pfizer.com/products/product-detail/viagra | access-date=17 June 2024}}</ref><ref>{{cite web | title=Brands | website=Viatris | date=16 November 2020 | url=https://www.viatris.com/en/products/brands | access-date=17 June 2024 | archive-date=17 June 2024 | archive-url=https://web.archive.org/web/20240617060406/https://www.viatris.com/en/products/brands | url-status=live }}</ref>

====Brazil====
Pfizer's patent on sildenafil citrate expired in Brazil in 2010.<ref>{{cite web|url=http://www.in-pharmatechnologist.com/Industry-Drivers/Viagra-patent-expires-in-June-says-Brazilian-court|title=Viagra patent expires in June, says Brazilian court|last=in-PharmaTechnologist.com|date=28 April 2010 |access-date=15 July 2016|archive-date=17 April 2012|archive-url=https://web.archive.org/web/20120417233636/http://www.in-pharmatechnologist.com/Industry-Drivers/Viagra-patent-expires-in-June-says-Brazilian-court|url-status=live}}</ref>

====Canada====
In Canada, Pfizer's patent 2,324,324 for Revatio (sildenafil used to treat pulmonary hypertension) was found invalid by the Federal Court in June 2010, on an application by [[Ratiopharm]] Inc.<ref>{{cite web |url=http://www.canadiantechnologyiplaw.com/2010/06/articles/intellectual-property/patents-1/revatio-patent-ruled-invalid-for-lack-of-sound-prediction-and-obviousness/ |publisher=Stikeman Elliott |work=Canadian Technology & IP Law |title=Revatio patent ruled invalid for lack of sound prediction and obviousness |date=18 June 2010 |access-date=14 November 2012 |archive-url=https://web.archive.org/web/20160303205830/http://www.canadiantechnologyiplaw.com/2010/06/articles/intellectual-property/patents-1/revatio-patent-ruled-invalid-for-lack-of-sound-prediction-and-obviousness/ |archive-date=3 March 2016 }}</ref><ref>{{cite web |url=http://canlii.ca/en/ca/fct/doc/2010/2010fc612/2010fc612.html |title=''Pfizer Canada Inc. v. Ratiopharm Inc.'', 2010 FC 612 |publisher=CanLII |access-date=27 December 2013 |archive-date=15 January 2013 |archive-url=https://archive.today/20130115095754/http://canlii.ca/en/ca/fct/doc/2010/2010fc612/2010fc612.html |url-status=live }}</ref>

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."<ref>{{cite CanLII|litigants=Teva Canada Ltd. v. Pfizer Canada Inc.|link=|year=2012|court=scc|num=60|pinpoint=par. 80|parallelcite=|date=8 November 2012|courtname=|juris=}}</ref>

Teva Canada launched Novo-Sildenafil, a generic version of Viagra, on the day the Supreme Court of Canada released its decision.<ref>{{cite news |url=https://www.thestar.com/business/2012/11/08/supreme_court_ruling_could_lead_to_cheaper_versions_of_viagra.html |work=[[Toronto Star]] |vauthors=Spears J |title=Supreme Court ruling could lead to cheaper versions of Viagra |date=8 November 2012 |access-date=14 November 2012 |archive-date=10 March 2013 |archive-url=https://web.archive.org/web/20130310084530/http://www.thestar.com/business/2012/11/08/supreme_court_ruling_could_lead_to_cheaper_versions_of_viagra.html |url-status=live }}</ref><ref>{{cite web |url=http://digitaljournal.com/article/336456 |work=Digital Journal |title=Canadian Supreme court rules Viagra patent invalid |vauthors=Hanly K |date=8 November 2012 |access-date=14 November 2012 |archive-date=11 November 2012 |archive-url=https://web.archive.org/web/20121111141433/http://digitaljournal.com/article/336456 |url-status=live }}</ref><ref>{{cite news |publisher=[[CBC News]] |url=http://www.cbc.ca/news/business/viagra-patent-tossed-out-by-supreme-court-1.1216466 |title=Viagra patent tossed out by Supreme Court: Decision allows generic versions of drug to be produced |access-date=14 November 2012 |date=8 November 2012 |archive-date=18 September 2013 |archive-url=https://web.archive.org/web/20130918100438/http://www.cbc.ca/news/business/viagra-patent-tossed-out-by-supreme-court-1.1216466 |url-status=live }}</ref> To remain competitive, Pfizer then reduced the price of Viagra in Canada.<ref>{{cite news |work=Financial Post |url=http://business.financialpost.com/2012/11/22/pfizer-canada-drops-viagra-price-generic-201/ |title=Pfizer Canada drops Viagra price after generic versions get Supreme Court green light |access-date=9 February 2013 |date=22 November 2012 |archive-date=30 November 2012 |archive-url=https://web.archive.org/web/20121130095322/http://business.financialpost.com/2012/11/22/pfizer-canada-drops-viagra-price-generic-201/ |url-status=live }}</ref> However, on 9 November 2012, Pfizer filed a motion for a re-hearing of the appeal in the Supreme Court of Canada,<ref>{{cite web |url=http://www.scc-csc.gc.ca/case-dossier/info/dock-regi-eng.aspx?cas=33951 |access-date=14 November 2012 |title=SCC Case Information, Docket No. 33951 |date=January 2001 |archive-date=27 December 2013 |archive-url=https://web.archive.org/web/20131227180306/http://www.scc-csc.gc.ca/case-dossier/info/dock-regi-eng.aspx?cas=33951 |url-status=live }}</ref> on the grounds that the court accidentally exceeded its jurisdiction by voiding the patent.<ref>{{cite news |vauthors=Makin K |work=The Globe and Mail |date=15 November 2012 |access-date=15 November 2012 |url=https://www.theglobeandmail.com/news/national/in-rare-move-pfizer-asks-supreme-court-to-reconsider-ruling-that-killed-viagra-patent/article5347670/ |title=In rare move, Pfizer asks Supreme Court to reconsider ruling that killed Viagra patent |archive-date=5 February 2013 |archive-url=https://web.archive.org/web/20130205050909/http://www.theglobeandmail.com/news/national/in-rare-move-pfizer-asks-supreme-court-to-reconsider-ruling-that-killed-viagra-patent/article5347670/ |url-status=live }}</ref> Finally, on 22 April 2013, the Supreme Court of Canada invalidated Pfizer's patent altogether.<ref>{{cite web |title=The Supreme Court of Canada holds Pfizer's Viagra patent invalid |vauthors=Henderson GL, D'Iorio H |work=Lexology |date=22 April 2013 |url=http://www.lexology.com/library/detail.aspx?g=63099904-cd62-4b40-a2e2-5112612e2da8 |access-date=27 December 2013 |archive-date=27 December 2013 |archive-url=https://web.archive.org/web/20131227123421/http://www.lexology.com/library/detail.aspx?g=63099904-cd62-4b40-a2e2-5112612e2da8 |url-status=live }}</ref>

====China====
{{unreferenced section|date=July 2024}}

Manufacture and sale of sildenafil citrate drugs is common in China, where Pfizer's patent claim is not widely enforced.

====Egypt====
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.<ref>{{cite news |title=Seeking Investment, Egypt Tries Patent Laws |vauthors=Allam A |url=https://www.nytimes.com/2002/10/04/business/seeking-investment-egypt-tries-patent-laws.html |newspaper=New York Times |date=4 October 2002 |access-date=1 April 2013 |archive-date=20 May 2013 |archive-url=https://web.archive.org/web/20130520125620/http://www.nytimes.com/2002/10/04/business/seeking-investment-egypt-tries-patent-laws.html |url-status=live }}</ref>

====European Union====
[[File:Sildenafil 100 milligram tablets - (prescription in the European Union) - Transgender shows the four-pack of 100 milligrams of tablet - Image 002n) - Transgender zeigt den Vierpack der je 100 Milligramm Tablette - Bild 002.jpg|thumb|upright=0.7|Sildenafil 100 milligram tablets (prescription in the European Union)]]
In June 2013 Pfizer's patent on sildenafil citrate expired in some member countries of the European Union, including Austria, Denmark, France, Germany, Ireland, Italy, The Netherlands, Spain, Sweden, the United Kingdom, and Switzerland.<ref>{{cite web|title=Actavis Launches Generic Viagra in Europe as Patents Expire|date=24 June 2013|url=https://finance.yahoo.com/news/actavis-launches-generic-viagra-r-120020258.html|access-date=25 October 2013|archive-date=29 October 2013|archive-url=https://web.archive.org/web/20131029201715/http://finance.yahoo.com/news/actavis-launches-generic-viagra-r-120020258.html|url-status=live}}</ref><ref name="What">{{cite web |url=http://www.accessrx.com/research/viagra-patent-expires |title=What Will Happen When Viagra Goes Generic? |vauthors=Edwards J |date=21 October 2009 |publisher=AccessRx.com |access-date=25 March 2011 |archive-date=23 April 2011 |archive-url=https://web.archive.org/web/20110423201812/http://www.accessrx.com/research/viagra-patent-expires |url-status=dead }}</ref><ref>{{cite news|title=Is Viagra about to lose its pulling power in the UK?|url=https://www.theguardian.com/business/shortcuts/2013/jun/03/viagra-lose-patent-pfizer-generic|newspaper=The Guardian|access-date=13 June 2013|date=3 June 2013|archive-date=30 October 2013|archive-url=https://web.archive.org/web/20131030182608/http://www.theguardian.com/business/shortcuts/2013/jun/03/viagra-lose-patent-pfizer-generic|url-status=live}}</ref> A UK patent held by Pfizer on the use of [[PDE5 inhibitor]]s (see below) as treatment of impotence was invalidated in 2000 because of [[Inventive step and non-obviousness|obviousness]]; this decision was upheld on appeal in 2002.<ref>{{cite news |url=https://www.telegraph.co.uk/money/main.jhtml?xml=/money/2002/01/24/cnviag24.xml |title=Viagra ruling upsets Pfizer |date=23 January 2002 |publisher=Telegraph Media Group Limited |access-date=10 February 2009 | location=London | vauthors = Murray R |url-status=dead |archive-url = https://web.archive.org/web/20090822222900/http://www.telegraph.co.uk/finance/2750418/Viagra-ruling-upsets-Pfizer.html|archive-date = 22 August 2009}}</ref><ref>{{cite web|url=http://www.urotoday.com/browse_categories/erectile_dysfunction/pfizer_loses_uk_battle_on_viagra_patent.html| title=Pfizer Loses UK Battle on Viagra Patent |date=17 June 2002 |publisher=Thomson Reuters |work=UroToday |access-date=10 February 2009|url-status = dead|archive-url = https://web.archive.org/web/20070625060239/http://www.urotoday.com/browse_categories/erectile_dysfunction/pfizer_loses_uk_battle_on_viagra_patent.html|archive-date = 25 June 2007}}</ref>

====India====
{{unreferenced section|date=July 2024}}

Manufacture and sale of sildenafil citrate drugs known as "generic Viagra" is common in India, where Pfizer's patent claim does not apply. Brand names include Kamagra ([[Ajanta Pharma]]), Silagra ([[Cipla]]), Edegra ([[Sun Pharmaceutical]]), Penegra ([[Zydus Cadila]]), Manly (Cooper Pharma) and Zenegra ([[Samprada Singh|Alkem Laboratories]]).

====New Zealand====
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 males could be referred for medical advice if appropriate.<ref>{{cite news|title=Viagra from the pharmacist: insight from reclassification in New Zealand|url=https://pharmaceutical-journal.com/article/opinion/viagra-from-the-pharmacist-insight-from-reclassification-in-new-zealand|vauthors=Gauld N|access-date=2 April 2018|publisher=Pharmaceutical Journal|date=31 January 2018|archive-date=17 May 2021|archive-url=https://web.archive.org/web/20210517195302/https://pharmaceutical-journal.com/article/opinion/viagra-from-the-pharmacist-insight-from-reclassification-in-new-zealand|url-status=live}}</ref>

====South Korea====
In 1999 South Korea granted two patents to Pfizer related to sildenafil. The first document guaranteed sole production and sale of the substance until 2012, while the second gave Pfizer the exclusive use to treating erectile dysfunction with sildenafil until 2014.<ref>{{Cite web|date=14 March 2012|title=Generic Viagra developers queue up, but may have to wait|url=http://www.koreaherald.com/view.php?ud=20120314001093|access-date=28 December 2021|website=The Korea Herald|archive-date=28 December 2021|archive-url=https://web.archive.org/web/20211228061652/http://www.koreaherald.com/view.php?ud=20120314001093|url-status=live}}</ref> In 2011 [[Hanmi Pharmaceutical]] and [[CJ CheilJedang]] launched a suit against the exclusive use patent. The Korean Court system made a ruling against Pfizer in June 2012, allowing for the unhindered domestic production of generic prescription sildenafil.<ref>{{Cite news|date=1 June 2012|title=Approved Viagra copies flood drugstores in Korea|work=Reuters|url=https://www.reuters.com/article/us-korea-viagra-idUSBRE8500KF20120601|access-date=28 December 2021|archive-date=28 December 2021|archive-url=https://web.archive.org/web/20211228061651/https://www.reuters.com/article/us-korea-viagra-idUSBRE8500KF20120601|url-status=live}}</ref>

During 2012 Viagra lost its position as the top selling erectile dysfunction treatment in South Korea. This development was credited largely "due to the introduction of generic products." Generic sildenafil became publicly available in May. Sales of PalPal by Hanmi Pharmaceuticals totalled ₩22 billion or about 86% the market share of Viagra that year.<ref>{{Cite web|date=10 April 2013|title=Viagra loses top spot in Korean market|url=http://www.koreaherald.com/view.php?ud=20130410000803|access-date=28 December 2021|website=The Korea Herald|archive-date=28 December 2021|archive-url=https://web.archive.org/web/20211228061651/http://www.koreaherald.com/view.php?ud=20130410000803|url-status=live}}</ref> By 2017 there were over 50 generic sildenafil pills available. During that year Viagra sales slumped to 38% that of Palpal.<ref>{{Cite web|date=12 December 2017|title=Hanmi leads erectile dysfunction drug sales|url=http://www.koreabiomed.com/news/articleView.html?idxno=2104|access-date=28 December 2021|website=KBR|language=ko|archive-date=28 December 2021|archive-url=https://web.archive.org/web/20211228061652/http://www.koreabiomed.com/news/articleView.html?idxno=2104|url-status=live}}</ref>

====United Kingdom====
There were 2,958,199 prescriptions for Sildenafil in 2016 in England, compared with 1,042,431 in 2006.<ref>{{cite web | title=Viagra prescriptions almost triple in a decade | website=The Pharmaceutical Journal | date=12 February 2021 | url=https://pharmaceutical-journal.com/article/news/viagra-prescriptions-almost-triple-in-a-decade | access-date=1 July 2024 | archive-date=1 July 2024 | archive-url=https://web.archive.org/web/20240701041224/https://pharmaceutical-journal.com/article/news/viagra-prescriptions-almost-triple-in-a-decade | url-status=live }}</ref>

In 2018, Viagra Connect, a particular formulation of Sildenafil marketed by Pfizer, became available for sale without a prescription in the UK,<ref name="The Independent"/> in an attempt to widen availability and reduce demand for counterfeit products.