In 2017, the Medicines and Healthcare products Regulatory Agency (MHRA) 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. On 6 May 2013, Pfizer, which manufactures Viagra, told the Associated Press they will begin selling the drug directly to people on its website.Pfizers 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 fifteen 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. Counterfeits
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.Viagra is one of the worlds most counterfeited medicines.
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)