Viagra has been recently reported to help in treating breast cancer, leukemia and sarcomas. As Viagra stabilizes the mitochondria and protects against free-radical damage of the mitochondria, which could other wise result in some serious situation. It has been also reported that it can be handy in removing clots; as Stents, which are installed in the arteries to maintain blood flow through them, the foreign materials of the devices, are recognized by the body and platelets often clot to them. If too many clot, this can block blood flow, potentially inducing a stroke or heart attack.

Robert F. Furchgott won the Nobel Prize in Physiology or Medicine in 1998 for his discovery and analysis of endothelium-derived relaxing factor (the inhibition of cGMP specific phosphodiesterase type 5 enzyme), a key part of the Sildenafil Nitrate mechanism of action.

For all the processes or functions to take place internally in the human body chemical reaction happens and for those chemical reactions to transpire; enzyme are require to occur at significant rates; where as enzymes are bi-molecules that catalyze chemical reactions.

In usual circumstances upon mental and sensory stimulation a penis transforms into an erected form and gets hard, as the blood starts to accumulate inside the penis through the chambers (one is for inflow of blood and one for outflow) called corpora cavernosa and spreads through out the penis via veins and arteries. The chambers open because the brain and local nerves causes the muscle of corpora cavernosa to relax and allow the blood to flow in but when the muscle contract it stops the inflow and thus the outflow process starts and thus the erection is lost.