| It has been estimated that ED affects 140 million males all over the world. Over than 50% of all males with ED are considered to have some physical (medical) cause. The rest are believed to have psychological causes of erectile dysfunction. Diabetes and circulatory, neurological or urological conditions are medical causes of impotence.
Erection occurs when the blood vessels delivering blood to the penis enhance the delivery of blood and the blood vessels removing blood from the penis reduce the removal of blood. In healthy men, sexual arousal causes the production and release of nitric oxide in the penis. Afterwards, nitric oxide activates the enzyme - guanylate cyclase - which triggers the production of cyclic guanosine monophosphate (cGMP). It is the cGMP that is chiefly responsible for the erection by regulating the quantity of blood that the blood vessels dilever and carry away from the penis.
Viagra is prescribed for the treatment of impotence of either medical or psychogenic condition. Viagra inhibits an enzyme called phosphodiesterase-5 (PDE5) that destroys the cGMP. Hence, sildenafil precludes 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.
Sildenafil is quickly absorbed. Maximum observed plasma concentrations are reached within 30 to 120 minutes of oral dosing in the fasted state. When sildenafil is taken with a high fat meal, the rate of absorption decreases, with maximum concentration observed in an hour.
Sildenafil increases the effects of heart drugs and nitrates that are used primarily for treating angina. Thus, drug-to-drug interactions with cardiac drugs and nitrates can be life-threatening.
Approximately 15% of men taking Viagra have side effects. The commonest side effects are redness in face, neck and/or chest (1 in 10), headaches (1 in 6), stomach pain, sickness, diarrhea, and an inability to differentiate between the colours green and blue.
Before taking sildenafil, consult your doctor. If you are allowed to use Viagra, stringently observe the recommended dose. |
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