Jet lag research
The 2007 Ig Nobel Prize in Aviation went to Patricia V. Agostino, Santiago A. Plano, and Diego A. Golombek of Universidad Nacional de Quilmes, Argentina, for their discovery that sildenafil helps treat jet lag recovery in hamsters. Sports
Professional athletes have been documented using sildenafil, believing the opening of their blood vessels will enrich their muscles. In turn, they believe it will enhance their performances. Analogs
Acetildenafil and other synthetic structural analogs of sildenafil which are PDE5 inhibitors have been found as adulterants in a number of "herbal" aphrodisiac products sold over-the-counter. These analogs have not undergone any of the rigorous testing that drugs like sildenafil have passed, and thus have unknown side-effect profiles. Some attempts have been made to ban these drugs, but progress has been slow so far, as, even in those jurisdictions that have laws targeting designer drugs, the laws are drafted to ban analogs of illegal drugs of abuse, rather than analogs of prescription medicines. However, at least one court case has resulted in a product being taken off the market.The U.S. Food and Drug Administration (FDA) has banned numerous products claiming to be Eurycoma longifolia that, in fact, contain only analogs of sildenafil. Sellers of such fake herbals typically respond by just changing the names of their products.
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.