How does Viagra work?

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.

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.

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" ...