Sildenafil Viagra works on a molecular level to treat erectile dysfunction by inhibiting the action of an enzyme called phosphodiesterase type 5 PDE5 . Here's a step-by-step explanation of how it works:1. In response to sexual stimulation, the body releases nitric oxide NO in the erectile tissue of the penis corpus cavernosum .2. Nitric oxide activates an enzyme called guanylate cyclase, which in turn increases the levels of cyclic guanosine monophosphate cGMP .3. The increased levels of cGMP cause the smooth muscle cells in the blood vessels of the corpus cavernosum to relax. This relaxation allows the blood vessels to dilate, increasing blood flow into the erectile tissue.4. The increased blood flow leads to an erection as the erectile tissue fills with blood and expands, causing the penis to become rigid.5. Under normal circumstances, the enzyme PDE5 breaks down cGMP, which causes the smooth muscle cells to contract and the blood vessels to constrict, ending the erection.Sildenafil Viagra works by inhibiting the action of PDE5, which prevents the breakdown of cGMP. This leads to increased levels of cGMP in the erectile tissue, promoting the relaxation of smooth muscle cells and dilation of blood vessels. As a result, blood flow to the erectile tissue is enhanced, and an erection is more easily achieved and maintained.It is important to note that Sildenafil Viagra does not cause an erection on its own; it merely enhances the natural erectile process in response to sexual stimulation.