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.

Who can it help?

The drug can help impotence associated with diabetes, spinal cord injuries, prostate surgery, and even impotence with mysterious causes. Viagra was tested on 3,000 men with varying degrees of impotence. It achieved a success rate of 60-80%, depending on the dosage.

Does it have side-effects?

In a small number of cases, people who have taken Viagra have complained of headaches, flushing and stomach-ache. It can also cause some visual problems, including an increased sensitivity to light, blurred vision or an inability to tell the difference between blue and green. Men who are already taking medicines that contain nitrates, such as nitro-glycerine, are strongly advised not to use Viagra because the combination can lower blood pressure too much. There are also concerns about its safety following the deaths of a small number of American men who have taken the drug. The Food and Drug Administration is investigating.

Some people in the UK are already taking Viagra. How is that possible?

Doctors in the UK can give a drug to a patient under what is known as the "named patient" arrangement. This allows the doctor to prescribe an unlicensed drug if they are satisfied that it is the right treatment and the patient takes full responsibility for anything that goes wrong.

What other treatments are available for impotence?

Many men use vacuum devices or compression rings to get and keep an erection. It is possible to have an injection in the base of the penis to increase the flow of blood. Surgery and implants are also an option in some cases. There are also several other prescriptions and over-the-counter pills that have been recommended for impotence problems in men, but none of these have ever been proven to be as effective as Viagra.

This page contains basic information. If you are concerned about your health, you should consult a doctor.