Viagra (sildenafil) is an oral drug treatment for erectile dysfunction (impotence) in men. It works by improving the blood flow to the penis, thus helping the patient achieve and maintain an erection when he is sexually stimulated. Viagra needs to be taken at least 30-60 minutes prior to sexual intercourse and remains active in the body for 4 hours. It can be taken as often as once a day. Viagra generally has mild side effects or none. However, like most medications, it is not suitable for all individuals and can be dangerous when used wrongly. Viagra is approved for use by adult men only and should not be used by women. http://www.penisenlargementz.com/cialis/generic_viagra.html