In a recent study, researchers find that for people with type 2 diabetes, switching to sulfonylurea drugs is linked to a higher risk of complications than staying on the drug metformin.
Metformin usually is the first drug that will be tried for patients with type 2 diabetes.
But sulfonylureas are the most commonly prescribed “second line” treatment, and often used in combination with metformin.
The safety of sulfonylureas has been studied extensively.
However, it is unclear if there is a specific risk of adding or switching to sulfonylureas compared with staying on metformin treatment alone.
In the study, McGill researchers examined whether adding or switching to sulfonylureas is associated with an increased risk of serious complications.
The team analyzed data from the UK Clinical Practice Research Datalink for over 77,000 patients (average age 64 years) with type 2 diabetes.
These patients started metformin treatment between 1998 and 2013.
Patients who subsequently added or switched to a sulfonylurea were identified and matched to a similar patient who continued metformin alone.
The researchers then used hospital records to monitor admissions for heart attack (myocardial infarction) and ischaemic stroke, cardiovascular death, death from any cause and dangerously low blood sugar levels.
They found that after one year, sulfonylurea use was linked to a higher risk of heart attack (7.8 v 6.2 per 1000 person-years), all-cause mortality (27.3 v 21.5), and severe low blood sugar (5.5 v 0.7), compared with continuing metformin alone.
There was also a trend towards increased risks of ischaemic stroke (6.7 v 5.5 per 1000 person-years) and cardiovascular death (9.4 v 8.1) with sulfonylurea use.
In addition, compared with adding sulfonylureas to metformin treatment, switching to sulfonylureas was linked to a higher risk of heart attack and all-cause mortality.
The researchers say they cannot rule out the possibility that some of the observed risks may be due to other unmeasured (confounding) factors.
They conclude that sulfonylureas as second-line drugs are linked to an increased risk of myocardial infarction, all-cause mortality, and severe hypoglycaemia, compared with remaining on metformin monotherapy.
Other researchers comment that this new evidence helps to individualize treatment decisions and minimize harm.
The research team is led by Professor Samy Suissa at McGill University in Canada.
The study is published in The BMJ.
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Journal reference: Sulfonylureas as second line drugs in type 2 diabetes and the risk of cardiovascular and hypoglycaemic events: population based cohort study, The BMJ, DOI: www.bmj.com/content/362/bmj.k2693.