Heart disease patients only got a “limited” benefit from a commonly used diabetes drug, the results of a new trial show.
Metformin is recommended as the first line of treatment for people with type 2 diabetes, cutting the overactive production of glucose.
Studies carried out before the common use of statins also showed that the drug cut other heart disease risk factors like cholesterol levels and inflammatory and blood clotting markers.
A UKPDS trial found diabetes patients who were given metformin saw their risk of having a heart attack cut by 39% over 10 years.
And expectations had been raised that the cardiovascular benefits would be replicated in people without diabetes.
The new randomised trial, whose results have been published in The Lancet Diabetes & Endocrinology, saw 173 non-diabetic heart disease patients given metformin or a placebo for 18 months.
At the end of the 18-month trial the patients who’d taken metformin showed no improvement in carotid intima-media thickness (cIMT), which increased significantly, or the extent of atherosclerotic plaque in the carotid arteries. Patients taking metformin were also more likely to suffer adverse events such as diarrhoea, vomiting and nausea.
But the metformin did have similar benefits to weight loss drugs, with patients taking it losing more than 3kg and experiencing reductions in their body fat, body mass index and waist circumference. Other risk factors for the development of type 2 diabetes were also improved, with participants recording lower insulin and haemoglobin A1c levels.
Dr David Preiss, one of the authors of the Carotid Atherosclerosis: Metformin for insulin Resistance (CAMERA) study, said: “We cannot dismiss the potential cardiovascular benefit of metformin in patients without diabetes but CAMERA suggests that metformin has limited impact on important cardiovascular risk factors when patients are already on a statin.”
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