Trials of a drug which could dramatically reduce the number of people having heart attacks and strokes in Britain have been halted ahead of schedule after producing outstanding results.

Researchers decided the trials had been so successful that it would be unfair to continue giving some patients a dummy version of the pill.

The magnitude of the benefit was so great we felt morally and ethically obliged to stop the trial

Professor Peter Sever

The tests show that the drug, atorvastatin, was effective on patients who had high blood pressure, but who would not normally be given treatment because their cholesterol levels were not excessively high.

Researcher Professor Peter Sever, from Imperial College London, told the BBC the trial, carried out on nearly 20,000 patients, was scheduled to run for five years, but had been stopped after three.

He said: "The magnitude of the benefit was so great in terms of reducing strokes and heart attacks that we felt morally and ethically obliged to stop the trial.

"We feel we have an obligation now - if the drug regulatory authorities allow us to - to offer the active drug to those who were previously receiving the dummy tablet."

Lifestyle measures not enough

The drug works by reducing levels of cholesterol, the build up of which is a major cause of heart disease.

Professor Sever said: "The problem in the Western world and in Britain in particular is that we have poor diets, we have a very high death rate from heart disease and strokes, and lifestyle measures are simply not adequate to reduce that risk."

The drug, produced by Pfizer under the name of Lipitor, has been available in the UK for several years, but has not previously been tested on patients who do not have high cholesterol levels.

The trial was designed to compare the effects of newer blood pressure drugs with standard therapies.

In addition, half the patients were given either atorvastatin or a placebo to measure the effects of lowering cholesterol in people who had high blood pressure, but relatively normal cholesterol levels.

Among the 5,000 patients who took atorvastatin, the risk of heart attacks or stroke was cut by a third.

Up to 50% of patients with high blood pressure also suffer from high cholesterol, and vice versa.

However, research has shown that patients with high blood pressure are more likely to be treated for their condition than are patients with high cholesterol.

In Britain, it is estimated that up to a million people with high cholesterol are either not diagnosed or not meeting their cholesterol targets with treatment.

Dr Joe Feczko, president of worldwide development at Pfizer, said: "We believe these results provide evidence that patients with high blood pressure and normal to slight elevation of cholesterol are at increased risk and can benefit from cholesterol lowering medication."

Atorvastatin cannot be prescribed for people with liver disease, or pregnant women.