Viagra is a medication used to treat erectile dysfunction. Viagra increases blood flow to the penis. It is a phosphodiesterase type 5 inhibitor, abbreviated PDE5 inhibitor. Drugs such as Viagra inhibit the effect of phosphodiesterase, an enzyme responsible for the destruction of cGMP. When cGMP (cyclic guanosine monophosphate) circulates, smooth muscles relax, and the blood vessels that supply blood to the penis dilate, facilitating erection by increasing blood flow.
Viagra acts selectively to target PDE5, promoting a cascade of events. Increased delivery of nitric oxide to the cells that line blood vessels (endothelium) occurs to relax and dilate the blood vessels and improve blood flow and produce erection. Nitric oxide plays an important role in blood vessel health and blood flow throughout the body, and is especially important to facilitate blood flow to the penis.
Viagra promotes blood flow and facilitates erection in preparation for sex. It does not increase libido. It works when a man is aroused, peaks in about one hour, and wears off after six hours. Viagra is known to be effective for men who experience performance anxiety, or experience psychological issues that inhibit erectile function.
Because Viagra relaxes the blood vessels, it can be dangerous if mixed with other drugs that do the same, such as nitroglycerin, used to treat angina. The result could be dangerously low blood pressure leading to heart attack. Viagra can cause headache, flushing and indigestion. The enzyme PDE6 is sometimes affected by Viagra. PDE6 enzyme is found in the eye. A warning from the FDA, placed in 2005, included information that some men had lost their eyesight after taking Viagra. A man should not use Viagra without clearance from his physician, especially if he has any history of cardiovascular disease or is on other medication. Viagra should always be obtained by prescription, following recommendation by a physician.
Viagra is especially helpful for people with diabetes. However, it does not work in all cases. Men with severe diseases of the blood vessels, severe neurologic disorders, advanced age and other metabolic disease may not respond to the effects of Viagra; 70 to 85 percent of men do respond to Viagra to treat erectile dysfunction. Viagra is not found in herbal preparations that carry names almost spelled like Viagra. Doses of Viagra include 25, 50 and 100 mg.
