China Greatvista Chemicals

Sildenafil Citrate (Viagra)

Sildenafil citrate is the active ingredient used to treat erectile dysfunction (impotence) in men. It can help men who have erectile dysfunction get and sustain an erection when they are sexually excited. One does not get an erection just by taking this medicine. Sildenafil citrate helps a man with erectile dysfunction get an erection only when he is sexually excited. Other drugs that operate by the same mechanism include Cialis and Levitra.

Sildenafil citrate relaxes muscles within the penis. This allows increased blood flow into the penis, necessary to achieve and maintain an erection. Sildenafil citrate treats erectile dysfunction, the inability to achieve and/or maintain an erection of the penis that is adequate for sexual intercourse. Ten to fifteen million men in the United States suffer from ED, and by age 65, up to 25% of men have experienced impotence problems. Erectile dysfunction can be caused by a number of physical and psychological conditions, including diabetes, depression, prostate cancer, spinal cord injury, multiple sclerosis, artherosclerosis, and heart disease. Injuries to the penis that cause nerve, tissue, or vascular damage can trigger impotence. It is also a common side effect of some prescription medications, including antihistamines, antidepressants, antihypertensives, antipsychotics, beta blockers, diuretics, tranquilizers, appetite suppressants, cimetidine (Tagamet), and finasteride (Propecia).

Sildenafil citrate enables many men with ED to respond to sexual stimulation. When a man is sexually aroused, the arteries in the penis relax and widen, allowing more blood to flow into the penis. As the arteries in the penis expand and harden, the veins that normally carry blood away from the penis become compressed, restricting the blood flow out of the penis. With more blood flowing in and less flowing out, the penis enlarges, resulting in an erection. Sildenafil inhibits the production of the PDE5 phosphate that is responsible for keeping the penis limp. Please understand that Generic Sildenafil Citrate is not a hormone or aphrodisiac, it works only when a man is sexually stimulated.

Sildenafil is a selective inhibitor of cGMP specific phosphodiesterase type 5 (PDE5) which is responsible for degradation of cGMP in the corpus cavernosum. Sildenafil has no direct relaxant effect on isolated human corpus cavernosum but enhances the relaxant effect of NO on this tissue. When the NO/cGMP pathway is activated, during sexual stimulation, inhibition of PDE5 by sildenafil results in increased corpus cavernosum levels of cGMP, producing smooth muscle relaxation in the corpus cavernosum allowing the inflow of blood. The physiologic mechanism of erection of the penis involves release of nitric oxide (NO) in the corpus cavernosum during sexual stimulation. NO then activates the enzyme guanylate cyclase, which results in increased levels of cyclic guanosine monophosphate (cGMP), producing smooth muscle relaxation in the corpus cavernosum and allowing inflow of blood. Sildenafil has no direct relaxant effect on isolated human corpus cavernosum, but enhances the effect of nitric oxide (NO) by inhibiting phosphodiesterase type 5 (PDE5), which is responsible for degradation of cGMP in the corpus cavernosum. When sexual stimulation causes local release of NO, inhibition of PDE5 by sildenafil causes increased levels of cGMP in the corpus cavernosum, resulting in smooth muscle relaxation and inflow of blood to the corpus cavernosum. Sildenafil at recommended doses has no effect in the absence of sexual stimulation.