82% of patients who take VIAGRA experience an improvement in their erections. That means more than 4 out of every 5 couples who try VIAGRA benefit from it. VIAGRA improves erections in most men regardless of how long they have had ED, what caused it, or how old they are. And the effectiveness of VIAGRA has been proven in clinical studies of thousands of patients.

VIAGRA enables many men with ED to respond to sexual stimulation. When a man is sexually aroused, the arteries in the penis relax and widen, allowing more blood to flow into the penis. As the arteries in the penis expand and harden, the veins that normally carry blood away from the penis become compressed, restricting the blood flow out of the penis. With more blood flowing in and less flowing out, the penis enlarges, resulting in an erection.

Viagra, also known as Sildenafil, does not directly give a man an erection. It works by boosting the natural mechanism that leads to an erection. When a man is sexually aroused, certain tissues in his penis relax. This allows large amounts of blood to flow into the muscle, thus producing an erection. Viagra helps by elevating the levels of the chemical that causes the tissues to relax. These effects were discovered accidentally. The drug was originally developed to improve blood supply to the heart in angina sufferers.