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.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. By 2017 there were over 50 generic sildenafil pills available. During that year Viagra sales slumped to 38% that of Palpal. United Kingdom
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. United States
Sildenafil is available as a generic drug in the United States, labeled 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. References
External links

"Sildenafil". Drug Information Portal. U.S. National Library of Medicine. "Sildenafil citrate". Drug Information Portal. U.S. National Library of Medicine. Viagra at The Periodic Table of Videos (University of Nottingham)