Erectile dysfunction, or ED, is a disorder where a man cannot achieve and maintain an erection of the penis. It can have dramatic effects on them and also their partner.

A recent survey of 1 000 men in the United Kingdom, aged between 18 and 75, showed that 39% reported experiencing some form of erectile dysfunction. In the United States, an estimated 30 million men suffer from the condition.

Many report depression and the condition can put a tremendous strain on their relationships.

Erectile dysfunction can be caused by a range of underlying problems. Vascular disease, smoking, diabetes, trauma to the spine, drug abuse and psychological problems can all contribute to the development of ED. Often, these can go untreated because the man suffering from ED is too embarassed to talk to his doctor, or even his partner, about the condition.

“After a while I thought his impotence was a sign he was no longer attracted to me. Eventually we pretty much avoided sex; this was one factor that led to our divorce.” Wife of Patient

The penis is filled with spongy tissue. It is fed by two arteries which can fill it with blood to make it turgid. When a man is stimulated, nervous signals from the brain cause the release of nitric oxide (NO) into these arteries. The arteries vasodilate and more blood is allowed to flow. The increased blood flow fills the tissue with blood to cause the erection.

Viagra™ works by enhancing and maintaining the dilation of the arteries and spongy tissue. This assists the ED sufferer to achieve and maintain an erection.

Click here to see an animation of this process.

The arteries that feed the spongy tissue in the penis dilate when they receive signals from the brain. The signal is carried by nitric oxide in the blood. It switches on the enzyme which makes a molecule known as cGMP (cyclic Guanosine Monophosphate). This triggers smooth muscle in the artery wall to relax and so the blood vessel dilates .

However, the cGMP is broken down by another enzyme known as PDE (Phosphodiesterase) causing the arteries to narrow again - bringing an end to the erection. Viagra™ inhibits the PDE and stops it from breaking down the cGMP. In this way, the natural erection is maintained. It doesn't last forever - only as long as the natural stimulation remains.