Most of the Active Pharmaceutical Ingredient (API) in Sildenafil, Sildenafil citrate, is produced in Pfizers Ringaskiddy complex, County Cork, which is Pfizers largest production facility outside of the United States. Medical uses
Sexual dysfunction
The primary indication of sildenafil is treatment of erectile dysfunction (inability to sustain a satisfactory erection to complete sexual intercourse). Its use is now one of the standard treatments for erectile dysfunction, including for men with diabetes mellitus. Antidepressant-associated sexual dysfunction
Tentative evidence suggests that sildenafil may help men who experience antidepressant-induced erectile dysfunction. Pulmonary hypertension
While sildenafil improves some markers of disease in people with pulmonary arterial hypertension, it does not appear to affect the risk of death or serious side effects. Raynauds phenomenon
Sildenafil and other PDE5 inhibitors are used off-label to alleviate vasospasm and treat severe ischemia and ulcers in fingers and toes for people with secondary Raynauds phenomenon; these drugs have moderate efficacy for reducing the frequency and duration of vasospastic episodes. As of 2016, their role more generally in Raynauds was not clear. High-altitude pulmonary edema
Sildenafil has been studied for high-altitude pulmonary edema, but its use is currently not recommended for that indication. Adverse effects
In clinical trials, the most common adverse effects of sildenafil use included headache, flushing, indigestion, nasal congestion, and impaired vision, including photophobia and blurred vision. Some sildenafil users have complained of seeing everything tinted blue (cyanopsia). This cyanopsia can be explained because Sildenafil, while selective for PDE5, does have a minor level of selectivity for PDE6, which is the phosphodiesterase found in the retina.
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).