Viagra

Before taking this medicine

Do not take Viagra if you: • Use nitric oxide donors, including nitrates or nitrites in any form, because Viagra can increase their blood-pressure-lowering effects. • Take a guanylate cyclase stimulator, such as riociguat. • Are allergic to sildenafil or any ingredient in the tablet. • Have a cardiovascular condition that makes sexual activity inadvisable. Extra caution is needed if you are prone to prolonged erections, have previously had non-arteritic anterior ischemic optic neuropathy (NAION, a condition that can cause vision loss), or have a “crowded” optic disc. If you have had NAION, Viagra should be used only when the expected benefits outweigh the risks. Tell your prescriber if you take alpha-blockers, blood pressure medicines or strong CYP inhibitors such as ritonavir. These can increase the risk of low blood pressure; increased sildenafil exposure can also cause fainting and prolonged erections. Older adults and people with severe kidney impairment or liver impairment may need their prescribed dose adjusted. Seek emergency treatment if an erection lasts more than four hours. Stop taking Viagra and seek medical care for sudden vision loss in either or both eyes, or prompt medical attention for a sudden decrease or loss of hearing.