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Viagra: Erections
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Unlike previously approved treatments for impotence, Viagra does not directly cause penis erection, but affects the response to sexual stimulation. The drug acts by enhancing the smooth muscle relaxation using nitric oxide, a chemical that is normally released in response to sexual stimulation. This smooth muscle relaxation allows increased blood flow into certain areas of the penis leading to an erection.
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Viagra opens blood vessels in the body, which allows for greater blood circulation to the penis during sexual stimulation. As the arteries of the penis harden and expand, blood flow out of the penis is restricted... causing an erection. After sexual activity, blood is allowed to flow out from the penis and the erection subsides.
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Viagra is the trademarked name for sildenafil citrate, a prescription drug created to counteract impotence by blocking an enzyme called phosphodiesterase 5 (PDE5), which can end erections prematurely. After the U.S. Food and Drug Administration granted approval for Viagra on 27 March 1998, doctors prescribed the drug more than any other medicine in history over a two-year time span. Pfizer Inc., the maker of Viagra, uses celebrities such as former senator Bob Dole and baseball star Rafael Palmeiro to advertise directly to consumers, contributing to the $15.7 billion total spent in 2000 on pharmaceutical ads targeted toward ordinary people—instead of doctors.
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Viagra is an oral drug for male impotence... known as erectile dysfunction (ED). It works by dilating blood vessels in the penis, allowing the inflow of blood needed for an erection.
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Viagra increases the blood flow to the penis by helping the arteries in the penis relax and expand. As the arteries in the penis expand and harden, veins that normally carry away blood flow to the penis are compressed resulting in an erection.
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Viagra® uses method number three -- it eliminates the PDE that is decomposing the cGMP, so cGMP builds up in the penis and has a larger effect on the artery walls. The greater the amount of cGMP the greater the blood flow, and the greater the blood flow the greater the degree of the erection.
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