I know it gives you an erection but how does it do that? And why does Viagra only work when the man is sexually stimulated?
How does Viagra work?
Question posted by aquanaut on 7 Aug 2009
Last updated on 2 January 2015
This question has also been asked and answered here: Cialis vs Viagra - What's the difference between them?
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3 Answers
Official Answer by Drugs.com
7 Aug 2009
Viagra works in response to sexual stimulation to increase the blood flow to the penis leading to an erection. Viagra does not result in an erection without sexual stimulation.
When a man is aroused, muscles in the penis relax to allow this greater blood flow. Viagra helps to elevate the levels of a substance (cyclic guanosine monophosphate, or cGMP) that causes the tissues to relax, leads to an inflow of blood, and causes an erection with sexual stimulation.
aquanaut
7 Aug 2009
So how does it relax the muscles?
suzanne66
8 Aug 2009
To understand how Viagra works we need to understand how an erection comes about.
Nitric Oxide (NO) is released with sexual stimulation from nerve endings and endothelial cells in the corpus cavernosum of the penis. An enzyme then converts guanosine triphosphate (GTP) into cyclic guanosine monophosphate (cGMP). cGMP causes the smooth muscle of the penis to relax, which causes an inflow of blood which then leads to an erection. cGMP is then hydrolysed back to the inactive GMP by phosphodiesteras type 5 (PDE5).
Men who suffer from erectile dysfunction often produce too little amounts of NO. This means that the small amount of cGMP they produce is broken down at the same rate and therefore doesn't have the time to accumulate and cause a prolonged vasodilation effect.
Sildenafil (Viagra) works by inhibiting the enzyme PDE5. This means that cGMP is not hydrolysed as fast and this allows the smooth muscle to relax.
Sildenafil is a potent and highly selective inhibitor of PDE5.
polymath48
2 Jan 2015
These meds only work when sexually aroused because the brain really is the master sex organ. Only when visual, tactile, or other stimuli cause the "thought" of sex are hormones released from the brain to begin the cascade of events that result in an erection. Sometimes something blocks a step toward that end. Viagra removes the block so things can proceed normally. Until the process begins, there is nothing for Viagra to do.
tark
7 July 2010
Simple notes how viagra work: Viagra Inhibits an enzyme called phosphodiesterase type 5 (PDE-5), making muscle in the penis more likely to relax and allowing blood to flow in, causing an erection.
rx2gostore
22 Feb 2010
When a man is sexually excited, viagra helps the penis fill with enough blood to cause an erection. it is taken about an hour before intercourse.
SandraLHoutz
2 July 2012
my hubby is usually good to go after 30 minutes of taking it ... but 45 minutes to an hour really allows the med to give him and me the full "effect" ...
Related topics
viagra, erectile dysfunction, sexual dysfunction
Further information
- Viagra uses and safety info
- Viagra prescribing info & package insert (for Health Professionals)
- Side effects of Viagra (detailed)
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