Contraindications
Contraindications include:
Concomitant use of nitric oxide donors, organic nitrites and nitrates, such as:
nitroglycerin
isosorbide mononitrate
isosorbide dinitrate
sodium nitroprusside
alkyl nitrites (commonly known as "poppers")
Concomitant use of soluble guanylyl cyclase stimulators, such as riociguat
Known hypersensitivity to sildenafilSildenafil should not be used if sexual activity is inadvisable due to underlying cardiovascular risk factors. Nonmedical use
Recreational use
Sildenafils popularity with young adults has increased over the years. Sildenafils trade name, Viagra, is widely recognized in popular culture, and the drugs association with treating erectile dysfunction has led to its recreational use. The reasons behind such use include the belief that the drug increases libido, improves sexual performance, or permanently increases penis size. Studies on the effects of sildenafil when used recreationally are limited, but suggest it has little effect when used by those who do not have erectile dysfunction. In one study, a 25 mg dose was shown to cause no significant change in erectile quality, but did reduce the postejaculatory refractory time. This study also noted a significant placebo effect in the control group.Unprescribed recreational use of sildenafil and other PDE5 inhibitors is noted as particularly high among users of illegal drugs. Sildenafil is sometimes used to counteract the effects of other substances, often illicit. Some users mix it with methylenedioxymethamphetamine (MDMA, ecstasy), other stimulants, or opiates in an attempt to compensate for the common side effect of erectile dysfunction, a combination known as "sextasy", "rockin and rollin" or "trail mix". Mixing it with amyl nitrite, another vasodilator, is particularly dangerous and potentially fatal.
Sildenafil, sold under the brand name Viagra, among others, is a medication used to treat erectile dysfunction and pulmonary arterial hypertension. It is unclear if it is effective for treating sexual dysfunction in women. It is taken by mouth or by injection into a vein. Onset 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 a prolonged erection (priapism) that can lead to damage to the penis, vision problems, and hearing loss. 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. 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 heart-related chest pain. It was approved for medical use in the United States and in the European Union in 1998. In 2017, it was the 217th-most commonly prescribed medication in the United States, with more than two million prescriptions. That same year, it also became available as a generic medication after final patents by Pfizer expired. In the United Kingdom, it is available over the counter.