The blood pressure drug, amlodipine (Pfizer's Norvasc), has seen another boost to its image after data unveiled at the World Cardiology Congress in Spain showed it cut the risk of developing new-onset diabetes by more than a third in patients with high blood pressure. The findings are from the world's largest study of hypertensive patients ever conducted in Europe, involving almost 20,000 patients.

The so-called ASCOT trial was initially set up to compare atenolol plus or minus a diuretic or amlodipine plus or minus the ACE inhibitor perindopril in controlling blood pressure. The impact of the study - which was halted early in 2004 - has had far-reaching effects in changing the way in which blood pressure is treated, and now this new analysis shows patients assigned to an amlodipine regimen were 34% less likely to develop diabetes over the five-year course of the study.

Of the 19.257 patients who enrolled in the study, 14,120 did not have diabetes at the outset but 1,366 developed the disease during the study period: 567 (8%) in the amlodipine arm and 799 (11.4%) in the atenolol arm. This could have far-reaching health consequences as both blood pressure and diabetes are risk factors for cardiovascular complications, including heart attack and stroke.

Moreover, taking aside other risk factors for diabetes - such as weight and high blood glucose levels at baseline - out of the equation, patients given the beta-blocker atenolol were significantly more at risk of developing new-onset diabetes. Overall, patients in the amlodipine arm saw an 11% reduction in total mortality, a 23% reduction in fatal and non-fatal strokes and a 24% reduction in cardiovascular death versus patients taking the beta-blocker.

This, say the researchers, provides further evidence for the move away from using beta-blockers in the treatment of hypertension. Earlier this year, the UK's National Institute for Health and Clinical Excellence issued recommendations not to use the older regimen, saying patients with high blood pressure under the age of 55 should now be treated in the first instance with an ACE inhibitor. But for those over the age of 55 and black patients, the first port of call should be a calcium channel blocker or thiazide-type diuretic.

Norvasc has lost patent protection in a number of markets around the world but is still Pfizer's second-largest product, with sales of $2.34 billion in the first half of this year mainly coming from the US market, where its patent armoury was recently upheld. These new data could add another string to the bow of its marketing weaponry, providing a healthy boost to its profit line.