VIAGRA works by opening the arteries. It was originally a heart medicine for angina. Too much and your blood pressure drops so low you may end up dead.
Cialis also works the same way, and my heart doctor warned me to stay away from it as if I do have to go to the hospital and they administer an artery opening drug it can kill me with low blood pressure.
Turns out this might be true....at least according to what you and others have posted with medical research. Stay healthy Ruy Dias de Bivar!