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Study prompts new debate on BP drugs after ranking them by diabetes risk

Diuretics head placebo in diabetes risk table

By Richard Hoey

Diuretics raise the risk of diabetes relative not only to other antihypertensive drugs but also to placebo, a major new analysis reveals.

The study, published in the latest issue of The Lancet, is the first to precisely compare each class of blood pressure medication in terms of diabetes risk.

Researchers used a new technique called network meta-analysis to compare drug classes and placebo controls even where trials had not done so directly.

They looked at 22 trials involving 143,153 patients.

ARBs and ACE inhibitors fared best, reducing diabetes risk compared with diuretics by 43 and 33 per cent respectively.

Calcium channel blockers reduced risk by 25 per cent and placebo, most surprisingly, by 23 per cent – again in comparison with diuretics.

Experts said the raised risk against placebo was surprising but consistent with NICE guidance, which gives doctors the option of using calcium channel blockers in patients with a high diabetes risk.

Study leader Dr Peter Meyer, associate professor of preventive medicine at Rush University Medical Center in Chicago, admitted the implications for clinical practice were 'uncertain'.

He said: 'In trials the absolute risk between drugs for diabetes was small and always less than 3.6 per cent. This and relatively short follow-up limit the power to detect increased risk of cardiovascular events in patients with [drug-related] diabetes.'

He pointed out that major trials including ALLHAT had seen no such increase in events with diuretics.

Professor Morris Brown, professor of clinical pharmacology at the University of Cambridge and president of the British Hypertension Society, said the raised risk compared with placebo was 'certainly' a new finding, but questioned its clinical significance.

Professor Brown, who is also honorary consultant physician at Addenbrooke's Hospital in Cambridge, said: 'There's still some debate about the significance of diabetes caused by drugs, which in theory should be reversible. In clinical practice you should stop the drug and see whether it gets any better.

'In people who haven't got any risk factors for diabetes I wouldn't have any hesitation in using thiazide diuretics, and if anything we should be using them at higher doses.'

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