The world's most commonly-used Type 2 diabetes drug could be used to treat non-diabetic conditions, according to Dundee University researchers.
An international study led by the university said there was "strong evidence" of metformin's anti-inflammatory properties.
The researchers said this "may prove significant" in relation to non-diabetic cardiovascular disease (CVD).
Metformin has been in use for more than 50 years.
The study said the drug "continues to reveal significant possibilities for treatments other than those for diabetes."
The drug is also undergoing new clinical trials to determine if it can promote healthy ageing.
The study is being led by Professor Chim Lang and Dr Graham Rena, from the university's division of molecular and clinical medicine.
Professor Lang said: "The anti-inflammatory effects of the drug were observed, not only in those with diabetes, but also in a cohort of non-diabetic heart failure patients."
Dr Rena said: "We found that this drug acts differently to nonsteroidal anti-inflammatory drugs by inhibiting a different target."
Dr Rena said the next step would be to establish exactly how the drug inhibits this target and to identify "specific non-diabetic" patient groups that benefit from the anti-inflammatory properties.
Prof Jeremy Pearson of the British Heart Foundation said: "These findings offer further evidence that old drugs can perform new tricks.
"Repurposed medicines can much more quickly benefit patients.
"If this existing and affordable drug can be repurposed as a heart disease treatment, then this is excellent news for the 2.3 million people in the UK living with the condition.
"We look forward to seeing how the research progresses in patient studies."