Viagra, also known as sildenafil citrate tablets, can be used mainly to improve male sexual function, it is suitable for the treatment of erectile dysfunction, the main active ingredient is sildenafil, sildenafil belongs to the specific type 5 phosphodiesterase selective inhibitor, the drug mainly by affecting the release of nitric oxide, so as to play a therapeutic effect, because the physiological mechanism of penile erection involves the penis during sexual stimulation The physiological mechanism of erection involves the release of nitric oxide in the corpus cavernosum, which activates guanylate cyclase, leading to increased levels of guanosine cyclophosphate, which relaxes smooth muscle in the corpus cavernosum and blood flow. Sildenafil mainly acts on this pathway, enhancing the release of nitric oxide, causing the blood to flow into the cavernous body, thus improving erectile dysfunction in the penis, which works under the condition of sexual stimulation. In short, Viagra is sildenafil, which can be used mainly to improve erectile dysfunction in men.