SCOTTISH scientists have revealed why some diabetics suffer side effects from a widely-used drug.

In an advance which takes treatment a step further along the road to personalised medicine, the researchers at Dundee University have uncovered a genetic quirk which helps explain why the treatment can trigger stomach complaints.

The researchers say their findings suggest patients who are suffering side effects from taking the drug metformin should review their prescribed treatment with their GP.

Metformin is the medication of choice for most patients with type 2 diabetes and is used by about 1.5 million people in the UK. It is known to have benefits over other diabetes therapies, yet approximately one in four patients suffer gastrointestinal side effects with this pill, and for 1 in 20 patients these side effects are so severe metformin cannot be used.

The research, published in the journal Diabetes, provides new insight into why some patients develop these side effects and how other commonly used treatments might increase the risk of suffering them.

Ms Tanja Dujic, who undertook the work at the Medical Research Institute at Dundee University, said: "Metformin is absorbed from the gut, in part, by a transporter called OCT1. Eight per cent of the population carry genetic variants that result in markedly reduced function of this OCT1 transporter. We showed that these people are nearly twice as likely to develop gastrointestinal side effects with metformin than people with normal OCT1 function."

However, the team believe it is not all down to genetics but that other prescribed drugs can also increase the risk of the side effects occurring.

Professor Ewan Pearson, who led the study, said: "There are a number of commonly used drugs, including anti-acid drugs such as omeprazole, and some blood pressure treatments such as doxazosin or verapamil, that also interact with the OCT1 transporter. People taking these drugs are also twice as likely to get side effects from metformin. And if you are one of the 8% who are genetically susceptible and are also taking one of these drugs your risks of side effects are increased more than four-fold."

He added: "We do need to follow up this observation with a careful clinical trial, but our findings certainly suggest that if you are suffering with gastrointestinal side effects whilst being treated with metformin, it would be worthwhile reviewing your other treatment with your GP, as one of them may be making the problem worse."