Sildenafil, sold under the brand name Viagra, among others, is a medication used to treat erectile dysfunction and pulmonary arterial hypertension. It is also sometimes used off-label for the treatment of certain symptoms in secondary Raynaud’s phenomenon. It is unclear if it is effective for treating sexual dysfunction in femalesIt can be taken orally (swallowed by mouth), intravenously (injection into a vein), or through the sublingual route (dissolved under the tongue). Onset when taken orally is typically within twenty minutes and lasts for about two hours.
Common side effects include headaches, heartburn, and flushed skin. Caution is advised in those with cardiovascular disease.Rare but serious side effects include vision problems, hearing loss, and prolonged erection (priapism) that can lead to damage to the penis. Sildenafil should not be taken by people on nitrates such as nitroglycerin (glycerin trinitrate), as this may result in a serious drop in blood pressure.]Sildenafil should not be taken within four hours of taking an alpha blocker.
Sildenafil acts by blocking phosphodiesterase 5 (PDE5), an enzyme that promotes breakdown of cGMP, which regulates blood flow in the penis. It requires sexual arousal to work, and does not by itself cause or increase sexual arousal.It also results in dilation of the blood vessels in the lungs.
Pfizer originally discovered the medication in 1989 while looking for a treatment for angina. It was approved for medical use in the United States and in the European Union in 1998.In 2020, it was the 183rd most commonly prescribed medication in the United States, with more than 2 million prescriptions. It is available as a generic medication. In the United Kingdom, it is available over the counter. Most of the active pharmaceutical ingredient, sildenafil citrate, is produced in Pfizer’s Ringaskiddy complex in County Cork, Ireland, which is Pfizer’s 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 males with diabetes mellitus.
Antidepressant-associated sexual dysfunction
Tentative evidence suggests that sildenafil may help males 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.
Raynaud’s 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 Raynaud’s phenomenon; these drugs have moderate efficacy for reducing the frequency and duration of vasospastic episodes.As of 2016, their role more generally in Raynaud’s was not clear.[22]
High-altitude pulmonary edema
Sildenafil has been studied for high-altitude pulmonary edema, but its use is currently not recommended for that indication.
