aquanautI know it gives you an erection but how does it do that? And why does Viagra only work when the man is sexually stimulated?
Answers (3)
Marvell7 Aug 2009
Viagra (sildenafil) relaxes muscles and increases blood flow to particular areas of the body.
Sildenafil under the name Viagra is used to treat erectile dysfunction (impotence) in men.
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So how does it relax the muscles?
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.