Diabetes drugs may increase risk of heart problems
5 December 2009
Their study found that people taking drugs called sulphonylureas are more likely to have heart attacks, heart failure or die, compared to people taking another popular diabetes drug called metformin. Doctors should choose metformin when treating people with diabetes, unless they can’t take it or it doesn’t work for them, say the researchers. A group of drugs commonly used for diabetes carry an increased risk of heart problems and death when compared with a different type of diabetes drug, researchers have found.
What we know already:
If you have type 2 diabetes, it means you have too much glucose in your blood. This can damage your blood vessels, causing heart attacks and strokes, as well as damage to smaller blood vessels in your kidneys, feet, and eyes. Some people with type 2 diabetes control their blood glucose through diet and exercise, but most people need diabetes medicines.The most commonly used drugs are metformin (brand name Glucophage), and a group of medicines called sulphonylureas. Sulphonyureas include the medicines chlorpropamide, glimepiride (Amaryl), glipizide (Glibenese, Minodiab), tolbutamide, glibenclamide (Daonil, Euglucon), and gliclazide (Diamicron).
Lately, there’s been concern that some of these drugs might increase your chances of having a heart attack or getting heart failure (where the heart can’t pump blood efficiently). It’s hard to pick up these problems in the clinical studies that are done before drugs are licensed, because they may take a long time to happen, and you need to test very large groups of people to pick up these sorts of differences in risk.Another group called glitazones (also known as thiazolidinediones) are also used. There are two types: rosiglitazone (Avandia) and pioglitazone (Actos).These medicines all help keep your blood glucose under control, although they work in different ways.
What does the new study say?
This new study looked at the risks of having a heart attack, getting heart failure, or dying for any reason while taking one or more of the commonly used diabetes drugs. The researchers used figures from a big database of prescribing information, cross-checked with patient records.The study found that people were more likely to die of any cause, or to get heart failure, while taking a sulphonylurea drug, compared with while taking metformin. They were also more likely to have a heart attack, although this link was not as strong.
Of the two glitazone drugs, pioglitazone seemed to be better than rosiglitazone, although the researchers say they need to see more studies to be sure of this. People were less likely to die of any cause while taking pioglitazone, compared with while taking rosiglitazone or metformin. Neither pioglitazone nor rosiglitazone was linked to more deaths or heart attacks than metformin, although rosiglitazone was linked to an increased chance of heart failure. Doctors are already warned not to prescribe rosiglitazone for people at risk of heart failure.
Where does the study come from?
The study was done by a team of researchers based at Imperial College in London, UK. It was published in the BMJ (British Medical Journal). The study was not directly funded by anyone, although some of the researchers received grants from various research programmes.
How reliable are the findings?
The good points of this study are that it covered a lot of people (more than 90,000) over an average of 7 years each. Because of the way the data was recorded, we can compare the risks and benefits of treatments as they’re actually prescribed, taking account of the fact that people tend to take more than one drug, or move from one drug to another over time.
However, this makes it harder to account for all the different factors that could affect the results.That might mean that people who took sulphonylureas were sicker than people who took metformin, so more likely to die of any cause. Also, the study relies on all the information on the databases being correctly entered at the time. Because this was a ‘real world’ study, rather than set up by researchers from the start, there’s likely to be more human error in terms of recording data than in a clinical trial.
What should to do?
All diabetes medicines protect against the problems you get from having too much glucose in your blood. It’s important not to stop taking medicines without talking to your doctor first. If you have diabetes and you haven’t been treated with metformin before, it may be worth discussing this with your doctor, especially if you’re overweight.
From:
Tzoulaki I, Molokhia M, Curcin V et al. Risk of cardiovascular disease and all cause mortality among patients with type 2 diabetes prescribed oral antidiabetes drugs: retrospective cohort study using UK general practice research database. BMJ 2009; 339: b4731.
© BMJ Publishing Group Limited (”BMJ Group”) 2009
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