. The main component of Viagra is Sildenafil Citrate. Sildenafil Citrate affects the response to sexual stimulation. It acts by enhancing smooth muscle relaxation using nitric oxide, a chemical that is normally released in response to sexual stimulation. This smooth muscle relaxation allows increased blood flow into certain areas of the penis, which leads to an erection. Sildenafil Citrate is applied for the treatment of erectile dysfunction (impotence) in men and pulmonary arterial hypertension. Sildenafil Citrate may also be used for other purposes not listed above.

. Cialis (tadalafil) relaxes muscles and increases blood flow to particular areas of the body. Cialis (tadalafil) is used to treat erectile dysfunction (impotence). Cialis (tadalafil) may also be used for purposes other than those listed in this medication guide.

is used to treat erection problems in men.