French study raises questions over metformin efficacy

A meta-analysis of 13 randomised controlled trials involving more than 13,000 patients found metformin alone or combined with a sulphonylurea did not reduce all-cause or cardiovascular mortality, nor did it result in fewer cases of leg amputations, peripheral vascular disease or microvascular complications. 

“A large number of patients have taken these treatments over many years even though there is the possibility of an overall unfavourable benefit/risk ratio,” the French authors wrote. 

“We cannot exclude a 25% reduction or a 31% increase in all-cause mortality,” they said. 

Professor Jonathan Shaw, associate director of the Baker IDI Heart and Diabetes Institute, agreed evidence was lacking. 

There had been uncertainty about the combination of metformin with sulphonylureas since adverse findings in the UK Prospective Diabetes Study, included in the analysis, he said.