Erectile Dysfunction Home > How Does Viagra Work?

Viagra, a prescription medication used to treat erectile dysfunction, works by blocking a chemical in the body that is normally responsible for reversing an erection. As a result, more of the chemicals responsible for the erection remain, so the muscles in the penis do not constrict. This allows blood to stay in the penis longer, which allows the man to maintain an erection. Because Viagra has no effect on the chemicals that cause an erection, it does not work without stimulation.

An Introduction to How Viagra Works

Viagra® (sildenafil citrate) is a medication that has been licensed to treat erectile dysfunction (ED), which is the repeated inability to get or keep an erection that is firm enough for sexual intercourse.
 
Viagra is very effective at treating erectile dysfunction. It works by blocking a chemical that causes blood to leave the penis. More blood in the penis means an improved erection.
 

Understanding Erections and Erectile Dysfunction

To understand how Viagra works, it may be helpful to understand erections.
 
When a man is aroused, nerve signals are sent from the brain and around the penis. These nerve signals cause chemicals to be released. These chemicals relax muscles in the penis. Normally, these muscles are constricted so that blood cannot flow into the penis. When these muscles relax, large amounts of blood are able to enter the penis, causing an erection. An erection is reversed when another chemical (known as phosphodiesterase type 5 [PDE5]) breaks down the chemicals that caused the muscles to relax in the first place. This causes the muscles in the penis to constrict again, which results in blood leaving the penis.
 

How Does Viagra Work?

Viagra works by blocking PDE5. When PDE5 is blocked, more of the chemicals responsible for the erection remain, so the muscles in the penis do not constrict. This allows blood to stay in the penis longer, which allows the man to maintain an erection.
 
Written by/reviewed by:
Last reviewed by: Kristi Monson, PharmD;
Last updated/reviewed:
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