Other drugs that interfere with the metabolism of sildenafil include erythromycin and cimetidine, both of which can also lead to prolonged plasma half-life levels. Those using protease inhibitors are recommended to limit their use of sildenafil to no more than one 25 mg dose every 48 hours. Protease inhibitors inhibit the metabolism of sildenafil, effectively multiplying the plasma levels of sildenafil, increasing the incidence and severity of side effects. InteractionsĬare should be exercised by people who are also taking protease inhibitors for the treatment of HIV infection. In October 2007, the FDA announced that the labeling for all PDE5 inhibitors, including sildenafil, required a more prominent warning of the potential risk of sudden hearing loss. Rare but serious adverse effects found through postmarketing surveillance include prolonged erections, severe low blood pressure, myocardial infarction (heart attack), ventricular arrhythmias, stroke, increased intraocular pressure, and sudden hearing loss. Food and Drug Administration (FDA) found that sildenafil could lead to vision impairment in rare cases, and a number of studies have linked sildenafil use with non-arteritic anterior ischemic optic neuropathy. Some complained of blurriness and loss of peripheral vision. Patients thus taking the drug may experience colorvision abnormalities. 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. Some sildenafil users have complained of seeing everything tinted blue ( cyanopsia). 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. Sildenafil has been studied for high-altitude pulmonary edema, but its use is currently not recommended for that indication. As of 2016, their role more generally in Raynaud's was not clear. 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. 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. Tentative evidence suggests that sildenafil may help men who experience antidepressant-induced erectile dysfunction. Antidepressant-associated sexual dysfunction Its use is now one of the standard treatments for erectile dysfunction, including for men with diabetes mellitus. The primary indication of sildenafil is treatment of erectile dysfunction (inability to sustain a satisfactory erection to complete sexual intercourse). Pfizer Viagra tablet in the trademark blue diamond shape Sexual dysfunction Most of the Active Pharmaceutical Ingredient (API) in Sildenafil, Sildenafil citrate, is produced in Pfizer's Ringaskiddy complex, County Cork, which is Pfizer's largest production facility outside of the United States. In the United Kingdom, it is available over the counter. That same year, it also became available as a generic medication after final patents by Pfizer expired. In 2017, it was the 217th-most commonly prescribed medication in the United States, with more than two million prescriptions. It was approved for medical use in the United States and in the European Union in 1998. Pfizer originally discovered the medication in 1989 while looking for a treatment for heart-related chest pain. It also results in dilation of the blood vessels in the lungs. Sildenafil acts by blocking phosphodiesterase 5 (PDE 5), an enzyme that promotes breakdown of cGMP, which regulates blood flow in the penis. Sildenafil should not be taken within four hours of taking an alpha blocker. 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. Rare but serious side effects include a prolonged erection (priapism) that can lead to damage to the penis, vision problems, and hearing loss.

Caution is advised in those with cardiovascular disease. Ĭommon side effects include headaches, heartburn, and flushed skin. Onset is typically within 20 minutes and lasts for about 2 hours. It is taken by mouth or by injection into a vein. It is unclear if it is effective for treating sexual dysfunction in women.

Sildenafil, sold under the brand name Viagra among others, is a medication used to treat erectile dysfunction and pulmonary arterial hypertension.

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