The American study of more than 2,500 patients foundthose takingdrugs known as calcium channel blockers had a 60 per cent greater risk of heart attack than those on the cheaper beta-blocking drugs or diuretics, also used forhigh blood pressure.
Dr Bruce Psaty, epidemiologist and lead researcher at Washington University, Seattle, said that if 1,000 patients with high blood pressure were treated with diuretics or beta-blockers for one year, about 10 may be expected to have a heart attack. If they were taking calcium channel blockers, the figuremay rise to 16.
The drugs studied included nifedipine, also known as Adalat, which is the world's second best-selling drug with sales in 1993 of more than £1,300m ($2080m);dilitiazem, ninth best-sellerwith sales of more than £950m ($1520m); and verapamil,number 23, on the list andworth more than £600m ($960m)worldwide.
The British Heart Foundation described the study as "interesting" but cautioned that more research was necessary and that patients on these drugs should not stop taking them.
However, the study is forcing doctors to rethink their strategies for treating high blood pressure, which affects 25 per cent ofadultsin the UK - about 14 million people - and isa lucrative medical market.
Between 8 and 12 per cent of people will need drug treatment to reduce their risk of stroke, kidney, heart damage and other problems. Calcium channel blockers are increasingly likely to be prescribed, according to John Swales, Professor of Medicine at Leicester University, and authority on hypertension.
Salim Yusuf, Professor of Cardiology at McMaster University, in Hamilton, Canada, believed that the Seattle study had raised real concerns. Calcium channel blockers had gained their market position through a combination of positive marketing, and over-emphasis on the adverse side-effects of diuretics.
Drug manufacturers reacted angrily to the study which was presented at the American Heart Association's annual conference in San Antonio, Texas, last month. According to Scrip, a British pharmaceutical newsletter, they claimed the study was flawed because it failed to distinguish between the effects of underlying disease and those of the drugs.
A spokesman for Bayer, manufacturer of Adalat, said that calcium antagonists have been widely used for high blood pressure and heart pain.
"The efficacy and safety of the drugs have been assessed in many controlled trials," he said.Reuse content