|It has been estimated that ED affects 140 million men worldwide. Over half of all males with ED are believed to have some organic (medical) condition. The rest are assumed to have psychogenic causes of erectile dysfunction. Medical causes of sexual dysfunction are diabetes and nerve damage, vascular disorders or abnormalities in the genital area.
Penile erection occurs when the blood vessels delivering blood to the organ boost the delivery of blood and the blood vessels removing blood from the penis reduce the removal of blood. In healthy men, sexual stimulation causes the production and release of nitric oxide in the penis. Nitric oxide then activates the enzyme, guanylate cyclase, which leads to the production of cyclic guanosine monophosphate (cGMP). It is the cGMP that control the quantity of blood is carried to and removed from the penis.
Viagra (sildenafil) is used for the treatment of ED of either medical or psychogenic condition. Viagra inhibits an enzyme known as phosphodiesterase-5 (PDE5) which destroys the cGMP. Thus, sildenafil prevents the destruction of cGMP and allows cGMP to increase in quantity and persist longer. The longer cGMP persists, the more prolonged the engorgement of the penis.
Viagra is quickly absorbed. Maximum observed plasma concentrations are reported within 30 to 120 minutes after oral administration in the fasted state. When Viagra is taken with a high-fat meal, the rate of absorption reduces.
Viagra increases the effects of heart drugs and nitrates that are used primarily for treating angina. Patients taking nitrates should not take Viagra.
About 15% of patients taking Viagra experience side effects. The commonest side effects are splitting headaches, dyspepsia, redness in face, neck and/or chest and visual changes. Infrequentcases of sudden loss of hearing have been reported with phosphodiesterase inhibitors, such as Viagra, at times with ringing in the ears and dizziness.
Before taking sildenafil, consult your medical practitioner. If your physician has prescribed you Viagra, stringently observe the recommended dosage.